| 1. |
- Doi, Yasuo, et al.
(författare)
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The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 899:1
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Tidskriftsartikel (refereegranskat)abstract
- We present new observations of the active star formation region NGC 1333 in the Perseus molecular cloud complex from the James Clerk Maxwell Telescope B-Fields In Star-forming Region Observations (BISTRO) survey with the POL-2 instrument. The BISTRO data cover the entire NGC 1333 complex (∼1.5 pc ? 2 pc) at 0.02 pc resolution and spatially resolve the polarized emission from individual filamentary structures for the first time. The inferred magnetic field structure is complex as a whole, with each individual filament aligned at different position angles relative to the local field orientation. We combine the BISTRO data with low- and high- resolution data derived from Planck and interferometers to study the multiscale magnetic field structure in this region. The magnetic field morphology drastically changes below a scale of ∼1 pc and remains continuous from the scales of filaments (∼0.1 pc) to that of protostellar envelopes (∼0.005 pc or ∼1000 au). Finally, we construct simple models in which we assume that the magnetic field is always perpendicular to the long axis of the filaments. We demonstrate that the observed variation of the relative orientation between the filament axes and the magnetic field angles are well reproduced by this model, taking into account the projection effects of the magnetic field and filaments relative to the plane of the sky. These projection effects may explain the apparent complexity of the magnetic field structure observed at the resolution of BISTRO data toward the filament network.
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| 2. |
- Psaltis, Dimitrios, et al.
(författare)
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Gravitational Test beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole
- 2020
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 125:14
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Tidskriftsartikel (refereegranskat)abstract
- The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to the first measurement of the size of a black-hole shadow. This observation offers a new and clean gravitational test of the black-hole metric in the strong-field regime. We show analytically that spacetimes that deviate from the Kerr metric but satisfy weak-field tests can lead to large deviations in the predicted black-hole shadows that are inconsistent with even the current EHT measurements. We use numerical calculations of regular, parametric, non-Kerr metrics to identify the common characteristic among these different parametrizations that control the predicted shadow size. We show that the shadow-size measurements place significant constraints on deviation parameters that control the second post-Newtonian and higher orders of each metric and are, therefore, inaccessible to weak-field tests. The new constraints are complementary to those imposed by observations of gravitational waves from stellar-mass sources.
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| 3. |
- Roelofs, F., et al.
(författare)
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SYMBA: An end-to-end VLBI synthetic data generation pipeline: Simulating Event Horizon Telescope observations of M 87
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 636
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Tidskriftsartikel (refereegranskat)abstract
- Context. Realistic synthetic observations of theoretical source models are essential for our understanding of real observational data. In using synthetic data, one can verify the extent to which source parameters can be recovered and evaluate how various data corruption effects can be calibrated. These studies are the most important when proposing observations of new sources, in the characterization of the capabilities of new or upgraded instruments, and when verifying model-based theoretical predictions in a direct comparison with observational data. Aims. We present the SYnthetic Measurement creator for long Baseline Arrays (SYMBA), a novel synthetic data generation pipeline for Very Long Baseline Interferometry (VLBI) observations. SYMBA takes into account several realistic atmospheric, instrumental, and calibration effects. Methods. We used SYMBA to create synthetic observations for the Event Horizon Telescope (EHT), a millimetre VLBI array, which has recently captured the first image of a black hole shadow. After testing SYMBA with simple source and corruption models, we study the importance of including all corruption and calibration effects, compared to the addition of thermal noise only. Using synthetic data based on two example general relativistic magnetohydrodynamics (GRMHD) model images of M 87, we performed case studies to assess the image quality that can be obtained with the current and future EHT array for different weather conditions. Results. Our synthetic observations show that the effects of atmospheric and instrumental corruptions on the measured visibilities are significant. Despite these effects, we demonstrate how the overall structure of our GRMHD source models can be recovered robustly with the EHT2017 array after performing calibration steps, which include fringe fitting, a priori amplitude and network calibration, and self-calibration. With the planned addition of new stations to the EHT array in the coming years, images could be reconstructed with higher angular resolution and dynamic range. In our case study, these improvements allowed for a distinction between a thermal and a non-thermal GRMHD model based on salient features in reconstructed images.
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| 4. |
- Wielgus, Maciek, et al.
(författare)
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Monitoring the Morphology of M87* in 2009-2017 with the Event Horizon Telescope
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 901:1
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Tidskriftsartikel (refereegranskat)abstract
- The Event Horizon Telescope (EHT) has recently delivered the first resolved images of M87*, the supermassive black hole in the center of the M87 galaxy. These images were produced using 230 GHz observations performed in 2017 April. Additional observations are required to investigate the persistence of the primary image feature-a ring with azimuthal brightness asymmetry-and to quantify the image variability on event horizon scales. To address this need, we analyze M87* data collected with prototype EHT arrays in 2009, 2011, 2012, and 2013. While these observations do not contain enough information to produce images, they are sufficient to constrain simple geometric models. We develop a modeling approach based on the framework utilized for the 2017 EHT data analysis and validate our procedures using synthetic data. Applying the same approach to the observational data sets, we find the M87* morphology in 2009-2017 to be consistent with a persistent asymmetric ring of similar to 40 mu as diameter. The position angle of the peak intensity varies in time. In particular, we find a significant difference between the position angle measured in 2013 and 2017. These variations are in broad agreement with predictions of a subset of general relativistic magnetohydrodynamic simulations. We show that quantifying the variability across multiple observational epochs has the potential to constrain the physical properties of the source, such as the accretion state or the black hole spin.
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| 5. |
- Kim, Tai Lim, et al.
(författare)
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Tea Consumption and Risk of Cancer: An Umbrella Review and Meta-Analysis of Observational Studies
- 2020
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Ingår i: ADVANCES IN NUTRITION. - : OXFORD UNIV PRESS. - 2161-8313. ; 11:6, s. 1437-1452
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Forskningsöversikt (refereegranskat)abstract
- Tea is one of the most widely consumed beverages, but its association with cancer risk remains controversial and unclear. We performed an umbrella review to clarify and determine the associations between tea consumption and various types of cancer by summarizing and recalculating the existing meta-analyses. Meta-analyses of observational studies reporting associations between tea consumption and cancer risk were searched on PubMed and Embase. Associations found to be statistically significant were further classified into levels of evidence (convincing, suggestive, or weak), based on P value, between-study heterogeneity, prediction intervals, and small study effects. Sixty-four observational studies (case-control or cohort) corresponding to 154 effect sizes on the incidence of 25 types of cancer were included. Forty-three (27.9%) results in 15 different types of cancer were statistically significant. When combining all studies on the same type of cancer, 19 results in 11 different types of cancer showed significant associations with lower risk of gastrointestinal tract organ cancer (oral, gastric, colorectal, biliary tract, and liver cancer), breast cancer, and gynecological cancer (endometrial and ovarian cancer) as well as leukemia, lung cancer, and thyroid cancer. Only the reduced risk of oral cancer in tea-consuming populations (OR = 0.62; 95% CI: 0.55, 0.72; P value < 10(-6)) was supported by convincing evidence. Suggestive evidence was found for 6 results on biliary tract, breast, endometrial, liver, and oral cancer.To summarize, tea consumption was shown to have protective effects on some types of cancer, particularly oral cancer. More well-designed prospective studies are needed with consideration of other factors that can cause biases.
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| 6. |
- Lee, Keum Hwa, et al.
(författare)
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Efficacy of Corticosteroids in Patients with SARS, MERS and COVID-19: A Systematic Review and Meta-Analysis
- 2020
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Ingår i: Journal of Clinical Medicine. - : MDPI. - 2077-0383. ; 9:8
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Forskningsöversikt (refereegranskat)abstract
- (1) Background: The use of corticosteroids in critical coronavirus infections, including severe acute respiratory syndrome (SARS), Middle East Respiratory Syndrome (MERS), or Coronavirus disease 2019 (COVID-19), has been controversial. However, a meta-analysis on the efficacy of steroids in treating these coronavirus infections is lacking. (2) Purpose: We assessed a methodological criticism on the quality of previous published meta-analyses and the risk of misleading conclusions with important therapeutic consequences. We also examined the evidence of the efficacy of corticosteroids in reducing mortality in SARS, MERS and COVID-19. (3) Methods: PubMed, MEDLINE, Embase, and Web of Science were used to identify studies published until 25 April 2020, that reported associations between steroid use and mortality in treating SARS/MERS/COVID-19. Two investigators screened and extracted data independently. Searches were restricted to studies on humans, and articles that did not report the exact number of patients in each group or data on mortality were excluded. We calculated odds ratios (ORs) or hazard ratios (HRs) under the fixed- and random-effect model. (4) Results: Eight articles (4051 patients) were eligible for inclusion. Among these selected studies, 3416 patients were diagnosed with SARS, 360 patients with MERS, and 275 with COVID-19; 60.3% patients were administered steroids. The meta-analyses including all studies showed no differences overall in terms of mortality (OR 1.152, 95% CI 0.631-2.101 in the random effects model,p= 0.645). However, this conclusion might be biased, because, in some studies, the patients in the steroid group had more severe symptoms than those in the control group. In contrast, when the meta-analysis was performed restricting only to studies that used appropriate adjustment (e.g., time, disease severity), there was a significant difference between the two groups (HR 0.378, 95% CI 0.221-0.646 in the random effects model,p< 0.0001). Although there was no difference in mortality when steroids were used in severe cases, there was a difference among the group with more underlying diseases (OR 3.133, 95% CI 1.670-5.877,p< 0.001). (5) Conclusions: To our knowledge, this study is the first comprehensive systematic review and meta-analysis providing the most accurate evidence on the effect of steroids in coronavirus infections. If not contraindicated, and in the absence of side effects, the use of steroids should be considered in coronavirus infection including COVID-19.
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| 7. |
- Kim, Hyung Min, et al.
(författare)
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Characterization and Antioxidant Activity Determination of Neutral and Acidic Polysaccharides from Panax Ginseng C. A. Meyer
- 2020
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Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 25:4
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Tidskriftsartikel (refereegranskat)abstract
- Panax ginseng (P. ginseng) is the most widely consumed herbal plant in Asia and is well-known for its various pharmacological properties. Many studies have been devoted to this natural product. However, polysaccharide’s components of ginseng and their biological effects have not been widely studied. In this study, white ginseng neutral polysaccharide (WGNP) and white ginseng acidic polysaccharide (WGAP) fractions were purified from P. ginseng roots. The chemical properties of WGNP and WGAP were investigated using various chromatography and spectroscopy techniques, including high-performance gel permeation chromatography, Fourier-transform infrared spectroscopy, and high-performance liquid chromatography with an ultra-violet detector. The antioxidant, anti-radical, and hydrogen peroxide scavenging activities were evaluated in vitro and in vivo using Caenorhabditis elegans as the model organism. Our in vitro data by ABTS (2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid), reducing power, ferrous ion chelating, and hydroxyl radical scavenging activity suggested that the WGAP with significantly higher uronic acid content and higher molecular weight exhibits a much stronger antioxidant effect as compared to that of WGNP. Similar antioxidant activity of WGAP was also confirmed in vivo by evaluating internal reactive oxygen species (ROS) concentration and lipid peroxidation. In conclusion, WGAP may be used as a natural antioxidant with potent scavenging and metal chelation properties.
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| 8. |
- Li, Shan Shan, et al.
(författare)
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Coupled U-Pb and Rb-Sr laser ablation geochronology trace Archean to Proterozoic crustal evolution in the Dharwar Craton, India
- 2020
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Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 343
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Tidskriftsartikel (refereegranskat)abstract
- © 2020 Elsevier B.V. The Western Dharwar Craton (WDC) and the Karwar Block (KB) in southern Peninsular India provide important windows to Earth's early crustal evolution and continental growth as these domains likely represent fragments of the first landmass or supercontinent on our planet. Here we employ, for the first time, a coupled laser ablation zircon U-Pb dating and in-situ Rb-Sr dating of micas (biotite, muscovite) and feldspars to evaluate the Meso- to Neoarchean crustal evolution and Proterozoic magmatism/metamorphism in the Karwar Block. This novel approach based on integrated geochronological results show that the WDC and KB experienced (i) a major Mesoarchean continental growth event (c. 3.2 to 2.9 Ga), (ii) younger Neoarchean and Paleoproterozoic magmatism/migmatization (syn- and post-tectonic granite formation events at c. 2.8–2.6 Ga and 2.2 Ga, respectively), and (iii) Mesoproterozoic metamorphism/thermal imprint (as young as 1.2 Ga). The zircon εHf(t) values exhibit a range from +0.4 to +9.8 in amphibolite, hornblende gneiss and trondhjemite (3.28–3.08 Ga), as well as the +6.1 to +9.7 range for 2.96 Ga old zircons in porphyritic granite, which suggests juvenile source for the magmatism that constructed this crustal block. Overall, this study illustrates the benefits of using coupled zircon U-Pb and in-situ Rb-Sr mica and feldspar dating approaches, as the former (U/Pb) provides robust constraints or a ‘baseline age’ for initial crystallization of crustal sequences whereas the latter (Rb/Sr) is sensitive to younger magmatic and metamorphic events. Thus, the integration of these two laser ablation ICP-MS based geochronometers applied to crustal evolution studies, has the potential to provide more comprehensive insights into continental growth in the early Earth, and later magmatic and metamorphic history of the region.
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| 9. |
- Qadri, Yazdan Ahmad, et al.
(författare)
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The Future of Healthcare Internet of Things: A Survey of Emerging Technologies
- 2020
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Ingår i: IEEE Communications Surveys and Tutorials. - : IEEE. - 1553-877X. ; 22:2, s. 1121-1167
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Tidskriftsartikel (refereegranskat)abstract
- The impact of the Internet of Things (IoT) on the advancement of the healthcare industry is immense. The ushering of the Medicine 4.0 has resulted in an increased effort to develop platforms, both at the hardware level as well as the underlying software level. This vision has led to the development of Healthcare IoT (H-IoT) systems. The basic enabling technologies include the communication systems between the sensing nodes and the processors; and the processing algorithms for generating an output from the data collected by the sensors. However, at present, these enabling technologies are also supported by several new technologies. The use of Artificial Intelligence (AI) has transformed the H-IoT systems at almost every level. The fog/edge paradigm is bringing the computing power close to the deployed network and hence mitigating many challenges in the process. While the big data allows handling an enormous amount of data. Additionally, the Software Defined Networks (SDNs) bring flexibility to the system while the blockchains are finding the most novel use cases in H-IoT systems. The Internet of Nano Things (IoNT) and Tactile Internet (TI) are driving the innovation in the H-IoT applications. This paper delves into the ways these technologies are transforming the H-IoT systems and also identifies the future course for improving the Quality of Service (QoS) using these new technologies.
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