bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quasi-periodic Particle Acceleration in a Solar Flare
Authors: Clarke Brendan P. , Hayes Laura A. , Gallagher Peter T. , Maloney Shane A. , Carley Eoin P. 
Published: April 2021

Abstract
A common feature of electromagnetic emission from solar flares is the presence of intensity pulsations that vary as a function of time. Known as quasi-periodic pulsations (QPPs), these variations in flux appear to include periodic components and characteristic timescales. Here, we analyze a GOES M3.7 class flare exhibiting pronounced QPPs across a broad band of wavelengths using imaging and time series analysis. We identify QPPs in the time series of X-ray, low-frequency radio, and extreme ultraviolet (EUV) wavelengths using wavelet analysis, and localize the region of the flare site from which the QPPs originate via X-ray and EUV imaging. It was found that the pulsations within the 171 Å, 1600 Å, soft X-ray, and hard X-ray light curves yielded similar periods of

s,

s,

s, and

s, respectively, indicating a common progenitor. The low-frequency radio emission at 2.5 MHz contained a longer period of ∼231 s. Imaging analysis indicates that the location of the X-ray and EUV pulsations originates from a hard X-ray footpoint linked to a system of nearby open magnetic field lines. Our results suggest that intermittent particle acceleration, likely due to “bursty” magnetic reconnection, is responsible for the QPPs. The precipitating electrons accelerated toward the chromosphere produce the X-ray and EUV pulsations, while the escaping electrons result in low-frequency radio pulses in the form of type III radio bursts. The modulation of the reconnection process, resulting in episodic particle acceleration, explains the presence of these QPPs across the entire spatial range of flaring emission.
On the Color–Metallicity Relation of the Red Clump and the Reddening toward the Magellanic Clouds
Authors: Nataf David M. , Cassisi Santi , Casagrande Luca , Yuan Wenlong , Riess Adam G. 
Published: April 2021

Abstract
The zero point of the reddening toward the Large Magellanic Cloud (LMC) has been the subject of some dispute. Its uncertainty propagates as a systematic error for methods that measure the extragalactic distance scale through knowledge of the absolute extinction of LMC stars. In an effort to resolve this issue, we used three different methods to calibrate the most widely used metric to predict LMC extinction, the intrinsic color of the red clump, (V − I)
RC,0, for the inner ∼3° of that galaxy. The first approach was to empirically calibrate the color zero points of the BaSTI isochrones over a wide metallicity range of Δ[Fe/H] ≈ 1.10 using measurements of red clump stars in 47 Tuc, the solar neighborhood, and NGC 6791. From these efforts, we also measure these properties of the solar neighborhood red clump, (V − I, G

BP
− K

s
, G − K

s
, G

RP
− K

s
, J − K

s
, H − K

s
, M

I
, M

Ks
)
RC,0 = (1.02, 2.75, 2.18, 1.52, 0.64, 0.15, −0.23, −1.63). The second and third methods were to compare the observed colors of the red clump to those of Cepheids and RR Lyrae in the LMC. With these three methods, we estimated the intrinsic color of the red clump of the LMC to be (V − I)
RC,0,LMC = {≈0.93, 0.91 ± 0.02, 0.89 ± 0.02}, respectively, and similarly, using the first and third methods, we estimated (V − I)
RC,0,SMC = {≈0.85, 0.84 ± 0.02}, respectively, for the Small Magellanic Cloud. We estimate the luminosities to be M

I,RC,LMC = −0.26 and M

I,RC,SMC = −0.37. We show that this has important implications for recent calibrations of the tip of the red giant branch in the Magellanic Clouds used to measure H
0.
Classical Novae Masquerading as Dwarf Novae? Outburst Properties of Cataclysmic Variables with ASAS-SN
Authors: Kawash A. , Chomiuk L. , Strader J. , Aydi E. , Sokolovsky K. V. , Jayasinghe T. , Kochanek C. S. , Schmeer P. , Stanek K. Z. , Mukai K. , Shappee B. , Way Z. , Basinger C. , Holoien T. W.-S. , Prieto J. L. 
Published: April 2021

Abstract
The unprecedented sky coverage and observing cadence of the All-Sky Automated Survey for SuperNovae (ASAS-SN) has resulted in the discovery and continued monitoring of a large sample of Galactic transients. The vast majority of these are accretion-powered dwarf nova outbursts in cataclysmic variable systems, but a small subset are thermonuclear-powered classical novae. Despite improved monitoring of the Galaxy for novae from ASAS-SN and other surveys, the observed Galactic nova rate is still lower than predictions. One way classical novae could be missed is if they are confused with the much larger population of dwarf novae. Here, we examine the properties of 1617 dwarf nova outbursts detected by ASAS-SN and compare them to classical novae. We find that the mean classical nova brightens by ∼11 mag during outburst, while the mean dwarf nova brightens by only ∼5 mag, with the outburst amplitude distributions overlapping by roughly 15%. For the first time, we show that the amplitude of an outburst and the time it takes to decline by two magnitudes from maximum are positively correlated for dwarf nova outbursts. For classical novae, we find that these quantities are negatively correlated, but only weakly, compared to the strong anticorrelation of these quantities found in some previous work. We show that, even if located at large distances, only a small number of putative dwarf novae could be misclassified as classical novae, suggesting that there is minimal confusion between these populations. Future spectroscopic follow-up of these candidates can show whether any are indeed classical novae.
Surveying the X-Ray Behavior of Novae as They Emit γ-Rays
Authors: Gordon A. C. , Aydi E. , Page K. L. , Li Kwan-Lok , Chomiuk L. , Sokolovsky K. V. , Mukai K. , Seitz J. 
Published: April 2021

Abstract
The detection of GeV γ-ray emission from Galactic novae by the Fermi-Large Area Telescope has become routine since 2010, and is generally associated with shocks internal to the nova ejecta. These shocks are also expected to heat plasma to ∼107 K, resulting in detectable X-ray emission. In this paper, we investigate 13 γ-ray emitting novae observed with the Neil Gehrels Swift Observatory, searching for 1–10 keV X-ray emission concurrent with γ-ray detections. We also analyze γ-ray observations of novae V407 Lup (2016) and V357 Mus (2018). We find that most novae do eventually show X-ray evidence of hot shocked plasma, but not until the γ-rays have faded below detectability. We suggest that the delayed rise of the X-ray emission is due to large absorbing columns and/or X-ray suppression by corrugated shock fronts. The only nova in our sample with a concurrent X-ray/γ-ray detection is also the only embedded nova (V407 Cyg). This exception supports a scenario where novae with giant companions produce shocks with external circumbinary material and are characterized by lower density environments, in comparison with novae with dwarf companions where shocks occur internal to the dense ejecta.
Hard X-Ray Emission Associated with White Dwarfs. IV. Signs of Accretion from Substellar Companions
Authors: Chu You-Hua , Toalá Jesús A. , Guerrero Martín A. , Bauer Florian F. , Bilikova Jana , Gruendl Robert A. 
Published: April 2021

Abstract
With an effective temperature of ≃200,000 K, KPD 0005+5106 is one of the hottest white dwarfs (WDs). ROSAT unexpectedly detected “hard” (∼1 keV) X-rays from this apparently single WD. We have obtained Chandra observations that confirm the spatial coincidence of this hard X-ray source with KPD 0005+5106. We have also obtained XMM-Newton observations of KPD 0005+5106, as well as PG 1159−035 and WD 0121−756, which are also apparently single and whose hard X-rays were detected by ROSAT at 3σ–4σ levels. The XMM-Newton spectra of the three WDs show remarkably similar shapes that can be fitted by models including a blackbody component for the stellar photospheric emission, a thermal plasma emission component, and a power-law component. Their X-ray luminosities in the 0.6–3.0 keV band range from 4 × 1029 to 4 × 1030 erg s−1. The XMM-Newton EPIC-pn soft-band (0.3–0.5 keV) light curve of KPD 0005+5106 is essentially constant, but the hard-band (0.6–3.0 keV) light curve shows periodic variations. An analysis of the generalized Lomb–Scargle periodograms for the XMM-Newton and Chandra hard-band light curves finds a convincing modulation (false-alarm probability of 0.41%) with a period of 4.7 ± 0.3 hr. Assuming that this period corresponds to a binary orbital period, the Roche radii of three viable types of companion have been calculated: M9V star, T brown dwarf, and Jupiter-like planet. Only the planet has a size larger than its Roche radius, although the M9V star and T brown dwarf may be heated by the WD and inflate past the Roche radius. Thus, all three types of companion may be donors to fuel accretion-powered hard X-ray emission.
Discovery and Characterization of a Rare Magnetic Hybrid β Cephei Slowly Pulsating B-type Star in an Eclipsing Binary in the Young Open Cluster NGC 6193
Authors: Stassun Keivan G. , Torres Guillermo , Johnston Cole , Stevens Daniel J. , Feliz Dax L. , Kounkel Marina , Bouma Luke G. 
Published: April 2021

Abstract
As many as 10% of OB-type stars have global magnetic fields, which is surprising given that their internal structure is radiative near the surface. A direct probe of internal structure is pulsations, and some OB-type stars exhibit pressure modes (β Cep pulsators) or gravity modes (slowly pulsating B-type stars; SPBs); a few rare cases of hybrid β Cep/SPBs occupy a narrow instability strip in the H-R diagram. The most precise fundamental properties of stars are obtained from eclipsing binaries (EBs), and those in clusters with known ages and metallicities provide the most stringent constraints on theory. Here we report the discovery that HD 149834 in the ∼5 Myr cluster NGC 6193 is an EB comprising a hybrid β Cep/SPB pulsator and a highly irradiated low-mass companion. We determine the masses, radii, and temperatures of both stars; the ∼9.7 M
⊙ primary resides in the instability strip where hybrid pulsations are theoretically predicted. The presence of both SPB and β Cep pulsations indicates that the system has a near-solar metallicity, and is in the second half of the main-sequence lifetime. The radius of the ∼1.2 M
⊙ companion is consistent with theoretical pre-main-sequence isochrones at 5 Myr, but its temperature is much higher than expected, perhaps due to irradiation by the primary. The radius of the primary is larger than expected, unless its metallicity is super-solar. Finally, the light curve shows residual modulation consistent with the rotation of the primary, and Chandra observations reveal a flare, both of which suggest the presence of starspots and thus magnetism on the primary.
Revisiting Current Concepts on the Tolerogenicity of Steady-State Dendritic Cell Subsets and Their Maturation Stages
Authors: Lutz Manfred B. , Backer Ronald A. , Clausen Björn E. 
Published: April 2021

Abstract
The original concept stated that immature dendritic cells (DC) act tolerogenically whereas mature DC behave strictly immunogenically. Meanwhile, it is also accepted that phenotypically mature stages of all conventional DC subsets can promote tolerance as steady-state migratory DC by transporting self-antigens to lymph nodes to exert unique functions on regulatory T cells. We propose that in vivo 1) there is little evidence for a tolerogenic function of immature DC during steady state such as CD4 T cell anergy induction, 2) all tolerance as steady-state migratory DC undergo common as well as subset-specific molecular changes, and 3) these changes differ by quantitative and qualitative markers from immunogenic DC, which allows one to clearly distinguish tolerogenic from immunogenic migratory DC.
Relationship between Cerebral Perfusion on Arterial Spin Labeling (ASL) MRI with Brain Volumetry and Cognitive Performance in Mild Cognitive Impairment and Dementia due to Alzheimer's Disease
Authors: Soman Shania , Raghavan Sheelakumari , Rajesh PG , Varma Ravi Prasad , Mohanan Nandini , Ramachandran Sushama S. , Thomas Bejoy , Kesavadas Chandrasekharan , Menon Ramshekhar N. 
Published: April 2021

Context:
Cerebral blood flow (CBF) measurement using arterial spin labelling (ASL) MRI sequences has recently emerged as a prominent tool in dementia research.

Aims:
To establish association between quantified regional cerebral perfusion and gray matter (GM) volumes with cognitive measures in mild cognitive impairment (MCI) and early Alzheimer's Dementia (AD), using three dimensional fast spin echo pseudo-continuous ASL MRI sequences.

Settings and Design:
Hospital-based cross-sectional study.

Methods and Material:
Three age-matched groups, i.e., 21 cognitively normal healthy controls (HC), 20 MCI and 19 early AD patients diagnosed using neuropsychological tests and who consented for multimodality 3T MRI were recruited for the study.

Statistical Analysis Used:
Statistical parametric mapping and regions of interest (ROI) multivariate analysis of variance was used to ascertain differences between patients and controls on MRI-volumetry and ASL. Linear regression was used to assess relationship between CBF with GM atrophy and neuropsychological test measures.

Results:
Compared to HC, patients with MCI and AD had significantly lower quantified perfusion in posterior cingulate and lingual gyri, over hippocampus in MCI, with no differences noted between MCI and AD. Atrophy over the middle temporal gyrus and hippocampus differentiated AD from MCI. No significant positive correlations were noted between perfusion and GM volumes in ROI with the exception of temporal neocortex. Significantly positive coefficient b-value (p < 0.01) were apparent between global cognition with CBF in precuneus, temporal neocortex and precuneus volume, with negative b-values noted between medial temporal CBF for global cognition and recall scores.

Conclusions:
ROI-based CBF measurements differentiated MCI and AD from HC; volumetry of medial and neocortical temporal GM separates AD from MCI. Correlations between CBF and neuropsychology are variable and require further longitudinal studies to gauge its predictive utility on cognitive trajectory in MCI.
Study of the efficiency and safety of subconjunctival triamcinolone acetonide in macular edema
Authors: Taoufik Abdellaoui , Yassmine Chaoui , Yassine Malek , Yassine Mouzari , Fouad Elasri , Karim Reda , Abdelbarre Oubaaz 
Published: April 2021

Purpose
To evaluate through a prospective study the efficiency and safety of triamcinolone in subconjunctival injection on macular edema (ME), in the short and medium term.

Patients and methods
All the patients included in the study underwent ophthalmologic examination and optic coherence tomography of the macula. The injection of 0.2–0.3 ml (8–12 mg) of triamcinolone was done in the subconjunctival space. We evaluated its efficiency by measuring the best-corrected visual acuity and the central macular thickness at 1, 3, and 6 months. Safety was evaluated by following up the intraocular pressure; the presence or absence of cataract and conjunctival complications at 1, 3, and 6 months; and the glycemic control.

Results
A total of 44 eyes (36 patients) were included. The overall best-corrected visual acuity and central macular thickness improved after injection. Overall, 67% of diabetic patients required reinjection at the third month. In the cases of inflammatory ME (uveitis and Irvine–Gass), the evolution has remained stable for 6 months after a single injection. No significant variation in intraocular pressure was noted after 1 month (P=0.38), after 3 months (P=0.20), or after 6 months (P=0.13). However, four patients developed ocular hypertension (10 mmHg or more above baseline), which has been well controlled with local monotherapy. Overall, 9.5% of phakic patients developed a cataract at the control of the sixth month. The change in glycated hemoglobin before and after the injection was not significant (P=0.84).

Conclusion
Subconjunctival triamcinolone acetonide seems to be an interesting and well-tolerated alternative therapy of ME in the short and medium term.
Evaluation of deep anterior lamellar keratoplasty for anterior corneal stromal pathology
Authors: Hashish Aya M. , Awad Eman A. , Sabry Dalia , El-Awady Hatem E. , El-Metwally Mohamed N. 
Published: April 2021

Settings
This study was conducted in Mansoura Ophthalmic Center, Mansoura University, Egypt, during the period from January 2018 to January 2019.

Purpose
This study aimed to evaluate the visual outcomes, topographic features, endothelial cell densities (ECD), and complications of deep anterior lamellar keratoplasty using big-bubble technique (BB-DALK) in different corneal stromal pathologies.

Patients and methods
This was a prospective, interventional study that included 24 eyes of 24 patients having corneal stromal pathologies, not involving Descemet membrane (DM) and endothelium. The primary outcome measures were the clinical, visual, and topographic outcomes (uncorrected visual acuity, best-corrected visual acuity, K1, and K2) throughout the follow-up period, whereas the secondary outcome measures were the refractive outcomes, central corneal thickness, ECD, and intraoperative and postoperative complications.

Results
A total of 21 (87.5%) patients underwent uneventful BB-DALK, and three (12.5%) cases were complicated by intraoperative DM microperforation who developed DM detachment and double anterior chamber (AC) postoperatively. One of them resolved spontaneously and the other two cases required intracameral air injection. Uncorrected visual acuity improved from 1.55±0.26 (logarithm of minimum angle of resolution) preoperatively to 0.63±0.2 1 year postoperatively (P<0.001) and best-corrected visual acuity improved from 1.08±0.11 (logarithm of minimum angle of resolution) to 0.30±0.12 (P=0.017). Refractive cylinder improved from −7.79±1.75 to −2.85±2.01 at 12 months of follow-up (P=0.007). Average K reading changed from 60.00±7.77 preoperatively to 43.43±2.98 postoperatively (P<0.001). Total ECD was 2248.08±431.13 by the end of the first year, with a mean of 8.2% endothelial cell loss. Loosening of the sutures occurred in five (20.8%) eyes between third and sixth months postoperatively. Urrets-Zavalia syndrome occurred in one of the two cases who were complicated with postoperative double AC and required intracameral air injection.

Conclusions
BB-DALK is an effective and safe technique for treatment of different corneal stromal pathologies sparing endothelium and DM.
Influence of Demographic Factors on Nerve Ultrasound of Healthy Participants in a Multiethnic Asian Population
Authors: Tan Cheng-Yin , Razali Siti Nur Omaira , Goh Khean-Jin , Shahrizaila Nortina 
Published: April 2021

Background:
High-resolution nerve ultrasound provides morphological information of peripheral nerves. We aimed to determine the normal ultrasonographic reference values of nerve cross-sectional area (CSA) in multiethnic Malaysian healthy participants.

Methods:
Nerve ultrasound of the median, ulnar, radial, tibial, fibular, and sural nerves was performed in 84 healthy participants at anatomical-defined locations. The CSA at each scanned site was measured by tracing circumferentially inside the hyperechoic rim of each nerve. Comparisons were made between genders and ethnic groups. Correlations with age, ethnicity, gender, height, weight, and body mass index (BMI) were evaluated.

Results:
CSA values and reference ranges in healthy participants were generated. Nerve CSA was significantly different in different gender (P = 0.002–0.032) and ethnic groups (P = 0.006–0.038). Men had larger nerve CSA than women, and Malay participants had larger nerve CSA compared to other ethnic groups. Nerve CSA had significant correlations to age, height, weight, and BMI (r = 0.220–0.349, P = 0.001–0.045).

Conclusion:
This study provides normative values for CSA of peripheral nerves in a multiethnic Malaysian population, which serves as reference values in the evaluation of peripheral nerve disorders. The ethnic differences in nerve CSA values should be considered during nerve ultrasound.
Mosquito Net Ownership, Utilization, and Preferences among Mobile and Migrant Populations Sleeping in Forests and Farms in Central Vietnam: A Cross-Sectional Study
Authors: Canavati Sara E. , Kelly Gerard C. , Vo Thuan Huu , Tran Long Khanh , Ngo Thang Duc , Tran Duong Thanh , Edgel Kimberly A. , Martin Nicholas J. 
Published: April 2021

ABSTRACTStrengthening vector control measures among mobile and migrant populations (MMPs) is crucial to malaria elimination, particularly in areas with multidrug-resistant malaria. Although a global priority, providing access and ensuring high coverage of available tools such as long-lasting insecticidal nets (LLINs) among these vulnerable groups remains a significant challenge. We assessed mosquito net ownership, utilization, and preference among individuals who slept in a forest and/or on a farm against those residing only in village “home” settings in a priority malaria elimination area of Vietnam. Proportions of respondents owning bed nets were similar among forest, farm, and home sleeping sites, ranging between 96% and 98%. The proportion of respondents owning hammock nets was higher for the forest group (92%), whereas ownership of hammocks in general was significantly lower for the home group (55%). Most respondents (97%) preferred to bring hammock nets to their remote sleeping site, whereas a smaller proportion (25%) also considered bed nets as an option. Respondent preferences included thick hammock nets with zippers (53%), hammocks with a flip cover (17%), and thin hammock nets with zippers (15%), with none choosing polyethylene (hard) LLINs. Although there is high coverage and access to nets for this high-priority MMP group, there was a noted gap between coverage and net use, potentially undermining the effectiveness of net-related interventions that could impact malaria prevention and elimination efforts in Vietnam. The design and material of nets are important factors for user preferences that appear to drive net use.
Impact of Testing on Sexually Transmitted Infections among Female Brothel Sex Workers in Bangladesh: A Randomized Controlled Trial
Authors: Islam Asad , Tan HongQi Alexis , Bristow Claire C. , Hasnain Md Golam , Smyth Russell , Wang Liang Choon 
Published: April 2021

Abstract.Past studies that have designed interventions to reduce the prevalence of sexually transmitted infections (STIs) have typically provided onsite treatment to sex workers who tested positive, which were expensive and difficult to implement. The purpose of this study was to examine the effect of an intervention which tested for STIs and provided information on the closest treatment facility on reducing the prevalence of STIs among female brothel-based sex workers (BSWs) in Bangladesh. The study adopted a pre–post interventional design as well as a randomized controlled study design. A baseline sample and follow-up urine sample were collected to evaluate the prevalence of STIs among participants in the treatment, but not control group. A baseline survey and interviews were also conducted for both the groups. The study found a nonsignificant reduction from baseline to follow-up in STI prevalence among intervention participants (adjusted odds ratio [aOR]: 0.74; 95% CI: 0.38, 1.45). However, the participants in the intervention group were significantly more likely to have a repeat client (aOR: 1.60; 95% CI: 1.12, 2.29) and nonsignificantly less likely to engage with a client suspected of having an STI (aOR: 0.62; 95% CI: 0.39, 1.00) than participants in the control group. The intervention testing of STIs and providing information to the positive cases about nearest treatment facilities were not effective in reducing the prevalence of STIs among BSWs. Further study of the clinical and behavioral impacts of such efforts to reduce STIs among BSWs is warranted.