المؤلفون: Kumar, Amit, Sharma, Kaushal, Vinkó, Jozsef, Steeghs, Danny, Gompertz, Benjamin, Lyman, Joseph, Dastidar, Raya, Singh, Avinash, Ackley, Kendall, Pursiainen, Miika

المصدر: Monthly Notices of the Royal Astronomical Society; Jul2024, Vol. 531 Issue 3, p3297-3309, 13p

مصطلحات موضوعية: MAGNETARS, GAMMA ray bursts, SUPERNOVAE, MACHINE learning, MEDIAN (Mathematics), LIGHT curves

مستخلص: We present the semi-analytical light curve modelling of 13 supernovae associated with gamma-ray bursts (GRB-SNe) along with two relativistic broad-lined (Ic-BL) SNe without GRB association (SNe 2009bb and 2012ap), considering millisecond magnetars as central-engine-based power sources for these events. The bolometric light curves of all 15 SNe in our sample are well-regenerated utilizing a χ²-minimization code, MINIM , and numerous parameters are constrained. The median values of ejecta mass (M ej), magnetar's initial spin period (P i), and magnetic field (B) for GRB-SNe are determined to be ≈5.2 M⊙, 20.5 ms, and 20.1 × 10¹⁴ G, respectively. We leverage machine learning (ML) algorithms to comprehensively compare the three-dimensional parameter space encompassing M ej, P i, and B for GRB-SNe determined herein to those of H-deficient superluminous SNe (SLSNe-I), fast blue optical transients (FBOTs), long GRBs (LGRBs), and short GRBs (SGRBs) obtained from the literature. The application of unsupervized ML clustering algorithms on the parameters M ej, P i, and B for GRB-SNe, SLSNe-I, and FBOTs yields a classification accuracy of ∼95 per cent. Extending these methods to classify GRB-SNe, SLSNe-I, LGRBs, and SGRBs based on P i and B values results in an accuracy of ∼84 per cent. Our investigations show that GRB-SNe and relativistic Ic-BL SNe presented in this study occupy different parameter spaces for M ej, P i, and B than those of SLSNe-I, FBOTs, LGRBs, and SGRBs. This indicates that magnetars with different P i and B can give birth to distinct types of transients. [ABSTRACT FROM AUTHOR]

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المؤلفون: Xie, Yushan, Shan, Huanyuan, Li, Nan, Li, Ran, Jullo, Eric, Su, Chen, Cao, Xiaoyue, Kneib, Jean-Paul, Acebron, Ana, He, Mengfan, Yao, Ji, Wang, Chunxiang, Li, Jiadong, Li, Yin

المصدر: Monthly Notices of the Royal Astronomical Society; Jun2024, Vol. 531 Issue 1, p1179-1190, 12p

مصطلحات موضوعية: PROPERTIES of matter, GRAVITATIONAL lenses, GALAXY clusters, MEDIAN (Mathematics), DARK energy, EQUATIONS of state, COSMOGRAPHY

مستخلص: Cluster-scale strong lensing is a powerful tool for exploring the properties of dark matter and constraining cosmological models. However, due to the complex parameter space, pixelized strong lens modelling in galaxy clusters is computationally expensive, leading to the point-source approximation of strongly lensed extended images, potentially introducing systematic biases. Herein, as the first paper of the ClUsteR strong Lens modelIng for the Next-Generation observations (CURLING) program, we use lensing ray-tracing simulations to quantify the biases and uncertainties arising from the point-like image approximation for JWST -like observations. Our results indicate that the approximation works well for reconstructing the total cluster mass distribution, but can bias the magnification measurements near critical curves and the constraints on the cosmological parameters, the total matter density of the universe Ωm, and dark energy equation of state parameter w. To mitigate the biases, we propose incorporating the extended surface brightness distribution of lensed sources into the modelling. This approach reduces the bias in magnification from 46.2 per cent to 0.09 per cent for μ ∼ 1000. Furthermore, the median values of cosmological parameters align more closely with the fiducial model. In addition to the improved accuracy, we also demonstrate that the constraining power can be substantially enhanced. In conclusion, it is necessary to model cluster-scale strong lenses with pixelized multiple images, especially for estimating the intrinsic luminosity of highly magnified sources and accurate cosmography in the era of high-precision observations. [ABSTRACT FROM AUTHOR]

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المؤلفون: Ward, B A, Eales, S A, Ivison, R J, Arumugam, V

المصدر: Monthly Notices of the Royal Astronomical Society; Jun2024, Vol. 530 Issue 4, p4887-4901, 15p

مصطلحات موضوعية: DUST, EMISSIVITY, GALAXIES, MEASUREMENT errors, INVERSE relationships (Mathematics), MEDIAN (Mathematics)

مستخلص: Variations in the dust emissivity index, |$\beta$|⁠ , within and between galaxies, are evidence that the chemistry and physics of dust must vary on large scales, although the nature of the physical and/or chemical variations is still unknown. In this paper, we estimate values of |$\beta$| and dust temperature for a sample of 109 dusty star-forming galaxies (DSFGs) over the range, |$2 \ \lt\ z \ \lt\ 6$|⁠. We compare the results obtained with both an optically thin model and a general opacity model, finding that our estimates of |$\beta$| are similar between the models but our estimates of dust temperature are not. We find no evidence of a change in |$\beta$| with redshift, with a median value of |$\beta = 1.96$| for the optically thin model with a confidence interval (16–84 per cent) of 1.67 to 2.35 for the population. Using simulations, we estimate the measurement errors from our procedure and show that the variation of |$\beta$| in the population results from intrinsic variations in the properties of the dust in DSFGs. At a fixed far-infrared luminosity, we find no evidence for a change in dust temperature, |$T_{\textrm {dust}}$|⁠ , with redshift. After allowing for the effects of correlated measurement errors, we find an inverse correlation between |$\beta$| and |$T_{\textrm {dust}}$| in DSFGs, for which there is also evidence in low-redshift galaxies. [ABSTRACT FROM AUTHOR]

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المؤلفون: Aly, Antar, Tsapaki, Virginia, Ahmed, Ayman Zakaria, Own, Ahmed, Patro, Satya, Naemi, Huda Al, Kharita, Mohammad Hassan

المصدر: Radiation Protection Dosimetry; Jun2024, Vol. 200 Issue 8, p755-762, 8p

مصطلحات موضوعية: CLINICAL indications, CEREBRAL arteriovenous malformations, NEURORADIOLOGY, CEREBROVASCULAR disease, MEDIAN (Mathematics), STROKE

مستخلص: This study focuses on patient radiation exposure in interventional neuroradiology (INR) procedures, a field that has advanced significantly since its inception in the 1980s. INR employs minimally invasive techniques to treat complex cerebrovascular diseases in the head, neck, and spine. The study establishes diagnostic reference levels (DRLs) for three clinical indications (CIs): stroke (S), brain aneurysms (ANs), and brain arteriovenous malformation (AVM). Data from 209 adult patients were analyzed, and DRLs were determined in terms of various dosimetric and technical quantities. For stroke, the established DRLs median values were found to be 78 Gy cm², 378 mGy, 118 mGy, 12 min, 442 images, and 15 runs. Similarly, DRLs for brain AN are 85 Gy cm², 611 mGy, 95.5 mGy, 19.5, 717 images, and 26 runs. For brain AVM, the DRL's are 180 Gy cm², 1144 mGy, 537 mGy, 36 min, 1375 images, and 31 runs. Notably, this study is unique in reporting DRLs for specific CIs within INR procedures, providing valuable insights for optimizing patient safety and radiation exposure management. [ABSTRACT FROM AUTHOR]

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المؤلفون: Ma, Yifu, Kong, Yuehong, Zhang, Shuying, Peng, Yong, Xu, Meiling, Zhang, Junjun, Xu, Hong, Hong, Zhihui, Xing, Pengfei, Qian, Jianjun, Zhang, Liyuan

المصدر: Journal of Radiation Research; May2024, Vol. 65 Issue 3, p337-349, 13p

مصطلحات موضوعية: LYMPHOPENIA, LYMPHOCYTE count, BLOOD cell count, MEDIAN (Mathematics), PROGRESSION-free survival, OVERALL survival

مستخلص: Lymphocytes, which are highly sensitive to radiation, play a crucial role in the body's defense against tumors. Radiation-induced lymphopenia has been associated with poorer outcomes in different cancer types. Despite being the largest secondary lymphoid organ, the spleen has not been officially designated as an organ at risk. This study hypothesizes a connection between spleen irradiation and lymphopenia and seeks to establish evidence-based dosage limits for the spleen. We retrospectively analyzed data from 96 patients with locally advanced gastric cancer who received postoperative chemoradiotherapy (CRT) between May 2010 and May 2017. Complete blood counts were collected before, during and after CRT. We established a model for predicting the minimum absolute lymphocyte count (Min ALC) and to investigate potential associations between spleen dosimetric variables and Min ALC. The median follow-up was 60 months. The 5-year overall survival (OS) and disease-free survival (DFS) were 65.2% and 56.8%, respectively. The median values of pre-treatment ALC, Min ALC and post-treatment ALC were 1.40 × 10⁹, 0.23 × 10⁹ and 0.28 × 10⁹/L, respectively. Regression analysis confirmed that the primary tumor location, number of fractions and spleen V5 were significant predictors of Min ALC during radiation therapy. Changes in ALC (ΔALC) were identified as an independent predictor of both OS and DFS. Spleen V5 is an independent predictor for Min ALC, and the maximum dose of the spleen is associated with an increased risk of severe lymphopenia. Therefore, these doses should be restricted in clinical practice. Additionally, ΔALC can serve as a prognostic indicator for adjuvant radiotherapy in gastric cancer. [ABSTRACT FROM AUTHOR]

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المؤلفون: Kopsacheili, Maria, Jiménez-Palau, Cristina, Galbany, Lluís, Boumis, Panayotis, González-Díaz., Raúl

المصدر: Monthly Notices of the Royal Astronomical Society; May2024, Vol. 530 Issue 1, p1078-1117, 40p

مصطلحات موضوعية: SUPERNOVA remnants, INTEGRAL field spectroscopy, LUMINOSITY, MEDIAN (Mathematics)

Reviews & Products: NEW General Catalogue of Nebulae & Clusters of Stars

مستخلص: In this study, we use MUSE Integral Field Spectroscopy (IFS), along with multiline diagnostics, for the optical identification of supernova remnants (SNRs) in the galaxy NGC 7793. We find in total 238 SNR candidates, 225 of them new identifications, increasing significantly the number of known SNRs in this galaxy. The velocity dispersion of the candidate SNRs was calculated, giving a mean value of |$\rm 27\, km\, s^{-1}$|⁠. We construct the H  |$\rm {\alpha }$|⁠ , [S  ii ], [O  iii ], and [S  ii ]–H  |$\rm {\alpha }$| luminosity functions, and for the first time, the [N  ii ], [N  iI ]–H  |$\rm {\alpha }$|⁠ , [N  ii ]–[S  ii ], [O  iii ]–[S  ii ], and [O  iii ]–[N  ii ] luminosity functions of the candidate SNRs. Shock models, along with the observed multiline information were used, in order to estimate shock velocities. The |$\rm \sim 65{{\ \rm per\ cent}}$| of the SNRs present velocities < 300  |$\rm km\, s^{-1}$|⁠. There is a clear correlation between shock velocity and [O  iii ]/H  |$\rm {\beta }$| ratio, and a less clear but still evident correlation in the relation between shock velocity and the [S  ii ]/H  |$\rm {\alpha }$|⁠ , [N  ii ]/H  |$\rm {\alpha }$| ratios. We also use the [S  ii ]6716/31 ratio of the SNR candidates to calculate their post-shock density, assuming different temperatures. The median value of the density of our sample is |$\rm \sim 80\, cm^{-3}$|⁠ , for a temperature of |$\rm T = 10^4\, K$|⁠. No correlation between shock velocity and density, or density and SNRs with [S  ii ]/H  |$\rm {\alpha }$| > 0.4 and [S  ii ]/H  |$\rm {\alpha }$| < 0.4 is observed. [ABSTRACT FROM AUTHOR]

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المؤلفون: Reyes-Reyes, S D, Stutz, A M, Megeath, S T, Xu, Fengwei, Álvarez-Gutiérrez, R H, Sandoval-Garrido, N, Liu, H -L

المصدر: Monthly Notices of the Royal Astronomical Society; Apr2024, Vol. 529 Issue 3, p2220-2233, 14p

مصطلحات موضوعية: STAR formation, PARALLAX, MEDIAN (Mathematics), MAGNETIC fields, FIBERS

مستخلص: While intensively studied, it remains unclear how the star formation (SF) in infrared dark clouds (IRDCs) compares to that of nearby clouds. We study G351.77-0.53 (henceforth G351), a cluster-forming filamentary IRDC. We begin by characterizing its young stellar object (YSO) content. Based on the average parallax of likely members, we obtain a Gaia distance of |$\sim \, 2.0\pm 0.14$|  kpc, resolving the literature distance ambiguity. Using our Herschel-derived N(H2) map, we measure a total gas mass of 10 200 M⊙ (within 11 pc²) and the average line-mass profile of the entire filament, which we model as |$\lambda =~1660 (w/\rm pc)^{0.62}\, \, {\rm M}_{\odot }\, \rm {pc}^{-1}$|⁠. At w < 0.63 pc, our λ profile is higher and has a steeper power-law index than λ profiles extracted in Orion A and most of its substructures. Based on the YSOs inside the filament area, we estimate the SF efficiency (SFE) and SF rate (SFR). We calculate a factor of 5 incompleteness correction for our YSO catalogue relative to Spitzer surveys of Orion A. The G351 SFE is ∼1.8 times lower than that of Orion A and lower than the median value for local clouds. We measure SFR and gas masses to estimate the efficiency per free-fall time, ϵff. We find that ϵff is ∼1.1 dex below the previously proposed mean local relation, and |$\sim \, 4.7\times$| below Orion A. These observations indicate that local SF-relations do not capture variations present in the Galaxy. We speculate that cloud youth and/or magnetic fields might account for the G351 inefficiency. [ABSTRACT FROM AUTHOR]

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المؤلفون: Issahaku, Shiraz, Boadu, Mary, Inkoom, Stephen, Hasford, Francis, Sackey, Theophilus A

المصدر: Radiation Protection Dosimetry; Apr2024, Vol. 200 Issue 6, p564-571, 8p

مصطلحات موضوعية: COMPUTED tomography, CONE beam computed tomography, MEDIAN (Mathematics), ADULTS, LUMBER

مستخلص: The International Atomic Energy Agency, as part of the new regional project (RAF/9/059), recommend the establishment of diagnostic reference levels (DRLs) in Africa. In response to this recommendation, this project was designed to establish and utilise national DRLs of routine computed tomography (CT) examinations. These were done by estimating CT dose index and dose length product (DLP) from a minimum of 20 patient dose report of the most frequently used procedures using 75th percentile distribution of the median values. In all, 22 centres that formed 54% of all CT equipment in the country took part in this study. Additionally, a total of 2156 adult patients dose report were randomly selected, with a percentage distribution of 60, 12, 21 and 7% for head, chest, abdomen–pelvis and lumber spine, respectively. The established DRL for volume CT dose index were 60.0, 15.7, 20.5 and 23.8 mGy for head, chest, abdomen–pelvis and lumber spine, respectively. While the established DRL for DLP were 962.9, 1102.8, 1393.5 and 824.6 mGy-cm for head, chest, abdomen–pelvis, and lumber spine, respectively. These preliminary results were comparable with data from 16 other African countries, European Commission and the International Commission on Radiological Protection. Hence, this study would serve as a baseline for the establishment of a more generalised regional and national adult DRLs for Africa and other developing countries. [ABSTRACT FROM AUTHOR]

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المؤلفون: Griffiths, R, Bardou, L, Butterley, T, Osborn, J, Wilson, R, Bustos, E, Tokovinin, A, Le Louarn, M, Otarola, A

المصدر: Monthly Notices of the Royal Astronomical Society; 3/30/2024, Vol. 529 Issue 1, p320-330, 11p

مصطلحات موضوعية: TURBULENCE, STANDARD deviations, SURFACE waves (Seismic waves), MEDIAN (Mathematics), MOTION, ATMOSPHERIC turbulence

مستخلص: A six-night optical turbulence monitoring campaign has been carried at Cerro Paranal observatory in 2023 February and March to facilitate the development and characterization of two novel atmospheric site monitoring instruments – the ring-image next-generation scintillation sensor (RINGSS) and 24-h Shack Hartmann image motion monitor (24hSHIMM) in the context of providing optical turbulence monitoring support for upcoming 20–40 m telescopes. Alongside these two instruments, the well-characterized Stereo-SCIDAR and 2016-MASS-DIMM were operated throughout the campaign to provide data for comparison. All instruments obtain estimates of optical turbulence profiles through statistical analysis of intensity and wavefront angle-of-arrival fluctuations from observations of stars. Contemporaneous measurements of the integrated turbulence parameters are compared and the ratios, bias, unbiased root mean square error, and correlation of results from each instrument assessed. Strong agreement was observed in measurements of seeing, free atmosphere seeing, and coherence time. Less correlation is seen for isoplanatic angle, although the median values agree well. Median turbulence parameters are further compared against long-term monitoring data from Paranal instruments. Profiles from the three small-telescope instruments are compared with the 100-layer profile from the stereo-SCIDAR. It is found that the RINGSS and SHIMM offer improved accuracy in characterization of the vertical optical turbulence profile over the MASS-DIMM. Finally, the first results of continuous optical turbulence monitoring at Paranal are presented which show a strong diurnal variation and predictable trend in the seeing. A value of 2.65 arcsec is found for the median daytime seeing. [ABSTRACT FROM AUTHOR]

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المؤلفون: Edmund, Elisha, Kamuzora, Mary, Muhogora, Wilbroad, Ngoya, Patrick, Muhulo, Alex, Amirali, Assad, Makoba, Atumaini, Ngoye, Wilson, Ngaile, Justin, Majatta, Salma, Ngulimi, Miguta, Mwambinga, Salome, Kaijage, Tunu

المصدر: Radiation Protection Dosimetry; Mar2024, Vol. 200 Issue 4, p409-416, 8p

مصطلحات موضوعية: DIGITAL mammography, BREAST, MEDIAN (Mathematics), RADIATION doses, MAMMOGRAMS, INFORMATION measurement

مصطلحات جغرافية: TANZANIA

مستخلص: The aim of this study was to evaluate the mean glandular dose (MGD), to assess the potential for optimization, and to propose diagnostic reference levels (DRLs). MGD was estimated from air kerma measurements and patient information collected during mammography examinations. The 75th percentile values were determined as the third quartile of the median MGD values for all hospitals, and DRLs set as 75th percentile of MGD values. The estimated median values of MGD ranged from 1.5 to 3.9 mGy for craniocaudal projection for median range of 15–59 mm compressed breast thickness (CBT). For a CBT range of 15–63 mm, the median MGD value was 1.5–5.1 mGy for medio-lateral oblique projection. Comparison with other studies showed that the MGD values obtained in this study were relatively high. The magnitude and wide variation of the exposure parameters suggest existing potential for optimization. The training of radiology staff was identified as a top priority. [ABSTRACT FROM AUTHOR]

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