bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Most Obscured AGNs in the XMM-SERVS Fields
Authors: Yan Wei , Brandt W. N. , Zou Fan , Zhu Shifu , Chen Chien-Ting J. , Hickox Ryan C. , Luo Bin , Ni Qingling , Alexander David M. , Bauer Franz E. , Vignali Cristian , Vito Fabio 
Published: June 2023

Abstract
We perform X-ray spectral analyses to derive the characteristics (e.g., column density, X-ray luminosity) of ≈10,200 active galactic nuclei (AGNs) in the XMM-Spitzer Extragalactic Representative Volume Survey, which was designed to investigate the growth of supermassive black holes across a wide dynamic range of cosmic environments. Using physical torus models (e.g., Borus02) and a Bayesian approach, we uncover 22 representative Compton-thick (CT; N
H > 1.5 × 1024 cm−2) AGN candidates with good signal-to-noise ratios as well as a large sample of 136 heavily obscured AGNs. We also find an increasing CT fraction (f
CT) from low (z < 0.75) to high (z > 0.75) redshift. Our CT candidates tend to show hard X-ray spectral shapes and dust extinction in their spectral energy distribution fits, which may shed light on the connection between AGN obscuration and host-galaxy evolution.
Distant Echoes of the Milky Way’s Last Major Merger
Authors: Chandra Vedant , Naidu Rohan P. , Conroy Charlie , Ji Alexander P. , Rix Hans-Walter , Bonaca Ana , Cargile Phillip A. , Han Jiwon Jesse , Johnson Benjamin D. , Ting 丁 Yuan-Sen 源森 , Woody Turner , Zaritsky Dennis 
Published: June 2023

Abstract
The majority of the Milky Way’s stellar halo consists of debris from our galaxy’s last major merger, the Gaia-Sausage-Enceladus (GSE). In the past few years, stars from the GSE have been kinematically and chemically studied in the inner 30 kpc of our galaxy. However, simulations predict that accreted debris could lie at greater distances, forming substructures in the outer halo. Here we derive metallicities and distances using Gaia DR3 XP spectra for an all-sky sample of luminous red giant stars, and map the outer halo with kinematics and metallicities out to 100 kpc. We obtain follow-up spectra of stars in two strong overdensities—including the previously identified outer Virgo Overdensity—and find them to be relatively metal rich and on predominantly retrograde orbits, matching predictions from simulations of the GSE merger. We argue that these are apocentric shells of GSE debris, forming 60–90 kpc counterparts to the 15–20 kpc shells that are known to dominate the inner stellar halo. Extending our search across the sky with literature radial velocities, we find evidence for a coherent stream of retrograde stars encircling the Milky Way from 50 to 100 kpc, in the same plane as the Sagittarius Stream but moving in the opposite direction. These are the first discoveries of distant and structured imprints from the GSE merger, cementing the picture of an inclined and retrograde collision that built up our galaxy’s stellar halo.
Mechanochemical Synthesis of Amorphous Silicates with an Enstatite and Forsterite Composition
Authors: Koike C. , Chihara H. 
Published: June 2023

Abstract
The presence of amorphous silicate particles in interstellar and circumstellar space has been suggested based on the observation of 9.7 and 18 μm emission bands. We have successfully synthesized amorphous silicate samples of an enstatite and forsterite composition by the mechanical milling of mixed powder consisting of SiO2–MgO and SiO2–Mg(OH)2 reagent-grade particles under different rotation frequencies and milling times. These two types of starting materials are prepared to study the effect of the OH bond on synthesis and crystallization. The amorphous samples were characterized by X-ray diffraction and infrared spectroscopy. Amorphous samples with enstatite composition are synthesized from both SiO2–MgO and SiO2–Mg(OH)2 at 300 rpm and for 300 hr. Amorphous samples with forsterite composition are synthesized from both SiO2–MgO and SiO2–Mg(OH)2. The samples from SiO2–Mg(OH)2 require 400 rpm and a long milling time of 1600 hr. After crystallization, amorphous samples with an enstatite composition synthesized from SiO2–Mg(OH)2 mainly transform into forsterite with small amounts of amorphous silica SiO2 and enstatite depending on the rotation frequencies and milling time, while those from SiO2–MgO become enstatite. The amorphous samples with a forsterite composition are crystallized to forsterite from both starting materials. The presence of H2O or OH bonds significantly affects the final products after the crystallization of amorphous silicates of enstatite composition.
Temperature of the Polar Inner Heliosheath: Connection to Solar Activity
Authors: Livadiotis G. , McComas D. J. , Zirnstein E. J. 
Published: June 2023

Abstract
We study the thermodynamics of the plasma protons in the polar regions of the inner heliosheath (IHS) and its connection with solar activity over solar cycle 24. First, we express the thermodynamic parameters of this plasma with respect to the year of energetic neutral atom (ENA) creation and perform a statistical analysis of temperatures, in order to provide a more precise characterization of the thermodynamics of IHS. Then, we perform an autocorrelation between the IHS temperature and the solar activity, using the proxies of sunspot number and fractional area of the polar coronal holes. We show that there is (i) high correlation between the time series of IHS proton temperatures and sunspot number, which is maximized for a time delay of τ ∼ 2.5 yr for both the north and south polar regions combined; (ii) high negative correlation between the temperature of the proton plasma in the north and south with the coronal hole fractional areas, where the time delay for the two poles combined is τ ∼ 2.71 ± 0.15 yr; and (iii) an asymmetry of a time-delay difference between the poles ∼0.22 yr, indicating that the southern polar ENA source region is ∼19 au closer than the northern one for a solar wind plasma protons of bulk speed of ∼400 km s−1. The findings demonstrate a connection between the IHS thermodynamics and solar activity through the solar wind, primarily manifested by the coronal holes expanding near solar minimum, which drives the expansion of fast solar wind over larger angles from high down to middle latitudes in the IHS.
Constraints on Undetected Long-period Binaries in the Known Pulsar Population
Authors: Jones Megan L. , Kaplan David L. , McLaughlin Maura A. , Lorimer Duncan R. 
Published: June 2023

Abstract
Although neutron star–black hole binaries have been identified through mergers detected in gravitational waves, a pulsar–black hole binary has yet to be detected. While short-period binaries are detectable due to a clear signal in the pulsar’s timing residuals, effects from a long-period binary could be masked by other timing effects, allowing them to go undetected. In particular, a long-period binary measured over a small subset of its orbital period could manifest via time derivatives of the spin frequency incompatible with isolated pulsar properties. We assess the possibility of pulsars having unknown companions in long-period binaries and put constraints on the range of binary properties that may remain undetected in current data, but that may be detectable with further observations. We find that for 35% of canonical pulsars with published higher-order derivatives, the precision of measurements is not enough to confidently reject binarity (period ≳2 kyr), and that a black hole binary companion could not be ruled out for a sample of pulsars without published constraints if the period is >1 kyr. While we find no convincing cases in the literature, we put more stringent limits on orbital period and longitude of periastron for the few pulsars with published higher-order frequency derivatives (n ≥ 3). We discuss the detectability of candidates and find that a sample pulsar in a 100 yr orbit could be detectable within 5–10 yr.
Investigating the Impact of Vertically Extended Coronae on X-Ray Reverberation Mapping
Authors: Lucchini Matteo , Mastroserio Guglielmo , Wang Jingyi , Kara Erin , Ingram Adam , Garcia Javier , Dauser Thomas , van der Klis Michiel , König Ole , Lewin Collin , Nathan Edward , Panagiotou Christos 
Published: June 2023

Abstract
Accreting black holes commonly exhibit hard X-ray emission, originating from a region of hot plasma near the central engine referred to as the corona. The origin and geometry of the corona are poorly understood, and models invoking either inflowing or outflowing material (or both) can successfully explain only parts of the observed phenomenology. In particular, recent works indicate that the time-averaged and variability property might originate in different regions of the corona. In this paper we present a model designed to move beyond the lamppost paradigm, with the goal of accounting for the vertical extent of the corona. In particular, we highlight the impact of including self-consistently a second lamppost, mimicking, for example, an extended jet base. We fully include the effect that the second source has on the time-dependent disk ionization, reflection spectrum, and reverberation lags. We also present an application of this new model to NICER observations of the X-ray binary MAXI J1820+070 near its hard-to-soft state transition. We demonstrate that in these observations, a vertically extended corona can capture both spectral and timing properties, while a single-lamppost model can not. In this scenario, the illumination responsible for the time-averaged spectrum originates close to the black hole, while the variability is likely associated with the ballistic jet.
First Evidence of Multi-iron Subpopulations in the Bulge Fossil Fragment Candidate Liller 1*
Authors: Crociati Chiara , Valenti Elena , Ferraro Francesco R. , Pallanca Cristina , Lanzoni Barbara , Cadelano Mario , Fanelli Cristiano , Origlia Livia , Leanza Silvia , Dalessandro Emanuele , Mucciarelli Alessio , Rich R. Michael 
Published: June 2023

Abstract
In the context of a project aimed at characterizing the properties of the so-called Bulge Fossil Fragments (the fossil remnants of the bulge formation epoch), here we present the first determination of the metallicity distribution of Liller 1. For a sample of 64 individual member stars we used ESO-MUSE spectra to measure the equivalent width of the Ca II triplet and then derive the iron abundance. To test the validity of the adopted calibration in the metal-rich regime, the procedure was first applied to three reference bulge globular clusters (NGC 6569, NGC 6440, and NGC 6528). In all the three cases, we found single-component iron distributions, with abundance values fully in agreement with those reported in the literature. The application of the same methodology to Liller 1 yielded, instead, a clear bimodal iron distribution, with a subsolar component at [Fe/H] = −0.48 dex (σ = 0.22) and a supersolar component at [Fe/H] = +0.26 dex (σ = 0.17). The latter is found to be significantly more centrally concentrated than the metal-poor population, as expected in a self-enrichment scenario and in agreement with that found in another bulge system, Terzan 5. The obtained metallicity distribution is astonishingly similar to that predicted by the reconstructed star formation history of Liller 1, which is characterized by three main bursts and a low, but constant, activity of star formation over the entire lifetime. These findings provide further support to the possibility that, similar to Terzan 5, Liller 1 is also a Bulge Fossil Fragment.
Energy Flux and Particle Flux in Steady-state Solutions of Nuclear Star Clusters
Authors: Rom Barak , Linial Itai , Sari Re’em 
Published: June 2023

Abstract
We examine the effects of two-body interactions in a nuclear star cluster surrounding a supermassive black hole. We evaluate the energy flux, analogously to the particle flux calculation of Bahcall and Wolf. We show that there are two types of power-law steady-state solutions: one with zero energy flux and constant particle flux and the other with constant energy flux and zero particle flux. We therefore prove that a zero particle flux solution, which corresponds to the case of an accreting supermassive black hole, can be obtained by requiring a constant energy flux. Consequently, this solution can be derived by simple dimensional analysis, bypassing the need for detailed calculation. Finally, we show that this characteristic, of zero particle flux for constant energy flux and vice versa, is not unique to the Keplerian potential of a supermassive black hole but holds for any central potential of the form ϕ ∝ r
−β
.
Regenerative endodontic treatment of immature permanent teeth after mechanical instrumentation with XP-Endo Finisher
Authors: Hristov Krasimir , Doitchinova Liliya , Gateva Natalia 
Published: June 2023

Introduction: The traditional treatment of immature permanent teeth with necrotic pulp involves creating an apical barrier by using calcium hydroxide or an MTA plug for an extended period of time. A novel therapeutic approach called regenerative endodontic procedures (REP) is used to allow root development to continue.
Aim: To investigate the response of immature permanent teeth and necrotic pulp to REP using a modified clinical protocol involving minimal mechanical instrumentation and irrigation with 10% citric acid.
Materials and methods: We treated 30 immature permanent teeth with necrotic pulp in 28 patients aged 7-14 years using a modified protocol for regenerative endodontics. The protocol included mechanical instrumentation of the root canal with the appropriate file for 2 minutes in total and irrigation with 10% citric acid.
Results: The root walls increased their thickness in 28 (93%) of the treated cases. In 16 (53%) cases, we found radiographic signs of continued root development; in six (20%), there was thickening of the canal walls and closure of the apex but no elongation; in four (13%), there was obliteration of the root canal; in two (7%), there was healing of the periapical lesion without any change in the length of the root walls or closure of the apex; and only two cases (7%) showed no signs of healing, but the teeth remained asymptomatic.
Conclusions: The use of mechanical instrumentation with the appropriate files in REP shortens the clinical protocol, which is advantageous when treating children’s dental issues.
Impact of gingival phenotype on the periodontal disease
Authors: Pashova-Tasseva Zdravka , Mlachkova Antoaneta , Tosheva Ekaterina 
Published: June 2023

Aim: The aims of the present study were to explore the relations between the gingival phenotype (GP) and the periodontal health status and find the prevalence of a specific gingival phenotype in a small Bulgarian population.
Materials and methods: We recruited 50 patients attending our dental practice with different periodontal diagnoses. A detailed periodontal status was taken to assess the diagnosis of each participant. Several clinical methods for evaluation of the gingival thickness and keratinized tissue width, including the TRAN method, transgingival probing, and direct measurement, were used. The data were summarized and analyzed statistically.
Results: We found a significant prevalence of the thick gingival phenotype, in particular the thick flat type. The patients with periodontitis had a higher distribution of the thick gingival phenotype, while in those with gingivitis, the thin scalloped gingival phenotype was noted. In regards to the gingival thickness (GT), 36 participants were found to have GT &gt;1 mm, and the remaining 14 had GT ≤1 mm. Statistically significant differences were found in the keratinized tissue width and the width of attached gingiva in the different gingival phenotypes. No significant differences were found in the age and sex of participants.
Conclusions: We found a significant prevalence of the thick (with a mild prevalence of thick flat to thick scalloped) versus thin gingival phenotype in the studied sample. The highest relative proportion of patients with periodontitis was among the subsample of individuals with thick flat gingival phenotype. Regarding gingivitis, the highest proportion was in the thin scalloped phenotype subsample – 42.9%. The highest prevalence of periodontal health was among the individuals with thick scalloped GP (50%), followed by the thin scalloped GP (35.7%).
Immunohistochemical phenotype of colorectal carcinoma in patients with KRAS mutation and mismatch repair status
Authors: Tashkova Desislava , Ilieva Nevena , Serteva Denitsa , Feodorova Yana , Mehterov Nikolay , Mollova Angelina , Bachurska Svitlana 
Published: June 2023

Introduction: Aberrant expression of CK7/CK20/CDX2 is reported in percentage of colorectal carcinomas (CRC).
Aim: The objective of this study was to investigate specific morphological and immunohistochemical characteristics of colorectal carcinoma with KRAS mutation status and microsatellite instability.
Materials and methods: Seventy-one patients with CRC and examined KRAS mutation status were included in the investigation. Immunohistochemistry was performed using antibodies to CK7, CK20, CDX2, PMS2, and MSH6. An automatic immunostainer (Ventana BenchMark GX) was used following the manufacturer’ instructions. Fisher’s exact test was used for statistical analysis (p value &lt;0.05).
Results: Immunohistochemical analysis was performed for CK7, CK20, CDX2, PMS2, and MSH6. Aberrant expression of the typical immunohistochemical profile CK7/CK20/CDX2 was observed in 50% of the cases. The highest sensitivity and specificity were established for CDX2, with 93% of the cases demonstrating positive nuclear expression in the tumor cells. As for the microsatellite status, 20% of the examined colorectal cancers showed loss in expression for one or both of the mismatch repair proteins - PMS2 and MSH6, which was associated with loss of expression for CK20 and CDX2 as well. Downhill correlation was found also between CK20 expression and the presence of mutation in the gene for KRAS.
Conclusions: Our results may support the heterogeneity of colorectal carcinoma. Statistically significant correlation was found between the expression of CK20 and CDX2 and microsatellite deficient and KRAS mutant colorectal cancers. This may lead to application of immunohistochemical screening panel for selection of patients with CRC for genetic testing. Further studies on large cohorts correlating different immunohistochemical profiles to molecular subtypes of colorectal carcinoma are needed for better understanding of the pathogenesis and behavior of colorectal carcinoma.
Comparative analysis of tensile strength between three types of retraction cords
Authors: Makakova Desislava R. , Alexandrov Svetlin , Vlahova Angelina 
Published: June 2023

Introduction: Gingival retraction is the withdrawal of the marginal gingiva away from the tooth. This procedure creates a space between the prepared tooth and the gingival tissues to catch more fine details of the impression material. The most common retraction device used in clinical practice is the retraction cord.
Aim: The study aims to evaluate the tensile strength of retraction cords designed with different braiding technology.
Materials and methods: A total of 150 experimental units were studied. They were divided into 3 groups of 50 each according to the type of retraction cord (Ultrapak #00, braided cord without core, and braided cord with monofilament core). We tested the tensile strength in the LMT 100 micro-tensile apparatus. The data were analyzed using SPSS v. 21. A critical significance level of p&lt;0.05 is used.
Results: The comparative analysis of the tensile strength of the retraction cords shows a statistically significant difference between the braided and the knitted threads (Ultrapak #00) (p&lt;0.001). The results indicated the highest tensile strength of the cord with monofilament 41.95 N/mm2, followed closely by the cord with the same cotton braid without monofilament with average strength of 39.80 N/mm2, and last came the Ultrapak cord 22.11 N/mm2.
Conclusions: The braided retraction cords show higher tensile strength compared to the Ultrapak #00 cord, which is made using knitting technology.
Extrapleural harvesting of the internal thoracic artery – impact on early postoperative results and pulmonary function
Authors: Kyuchukov Dimitar , Stoycheva Stanislava , Nachev Gencho 
Published: June 2023

Introduction: The internal thoracic artery (ITA) has proven to be the best graft for surgical myocardial revascularization, especially in the configuration left ITA (LITA) to the anterior descending branch of left coronary artery (LAD). Its harvesting is usually accompanied by pleurotomy, followed by drainage tube placement into the pleural cavity, using the so called intrapleural method. Extrapleural technique for LITA harvesting is also practiced in many cardiac surgery centers and with this technique the pleura is left intact.
Aim: The aim of our study was to investigate the impact of both techniques of LITA harvesting on lung function and incidence of postoperative complications early after operation.
Materials and methods: We analyzed retrospectively data of 82 operated patients scheduled for surgical myocardial revascularization and meeting certain inclusion and exclusion criteria. The patients were divided into two groups depending on the way LITA was prepared. Lung parameters and incidence of surgical complications were registered in the early postoperative period until day 30.
Results: The patients from both groups had similar preoperative characteristics and risk factors. Those with preserved pleura showed significantly better results of the studied pulmonary parameters and lower complications event rate during early postoperative follow-up.
Conclusions: Maintaining the pleura integrity during LITA harvesting is beneficial for lung function and reduces the rate of complications in the early postoperative period.