| 1. |
- Akiyama, Kazunori, et al.
(författare)
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First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization
- 2023
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Ingår i: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 957:2
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Tidskriftsartikel (refereegranskat)abstract
- Event Horizon Telescope (EHT) observations have revealed a bright ring of emission around the supermassive black hole at the center of the M87 galaxy. EHT images in linear polarization have further identified a coherent spiral pattern around the black hole, produced from ordered magnetic fields threading the emitting plasma. Here we present the first analysis of circular polarization using EHT data, acquired in 2017, which can potentially provide additional insights into the magnetic fields and plasma composition near the black hole. Interferometric closure quantities provide convincing evidence for the presence of circularly polarized emission on event-horizon scales. We produce images of the circular polarization using both traditional and newly developed methods. All methods find a moderate level of resolved circular polarization across the image (〈|v|〉 < 3.7%), consistent with the low image-integrated circular polarization fraction measured by the Atacama Large Millimeter/submillimeter Array (|vint| < 1%). Despite this broad agreement, the methods show substantial variation in the morphology of the circularly polarized emission, indicating that our conclusions are strongly dependent on the imaging assumptions because of the limited baseline coverage, uncertain telescope gain calibration, and weakly polarized signal. We include this upper limit in an updated comparison to general relativistic magnetohydrodynamic simulation models. This analysis reinforces the previously reported preference for magnetically arrested accretion flow models. We find that most simulations naturally produce a low level of circular polarization consistent with our upper limit and that Faraday conversion is likely the dominant production mechanism for circular polarization at 230 GHz in M87*
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| 2. |
- Roelofs, F., et al.
(författare)
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Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes
- 2023
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Ingår i: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 957:2
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Tidskriftsartikel (refereegranskat)abstract
- The Event Horizon Telescope (EHT) is a millimeter very long baseline interferometry (VLBI) array that has imaged the apparent shadows of the supermassive black holes M87* and Sagittarius A*. Polarimetric data from these observations contain a wealth of information on the black hole and accretion flow properties. In this work, we develop polarimetric geometric modeling methods for mm-VLBI data, focusing on approaches that fit data products with differing degrees of invariance to broad classes of calibration errors. We establish a fitting procedure using a polarimetric “m-ring” model to approximate the image structure near a black hole. By fitting this model to synthetic EHT data from general relativistic magnetohydrodynamic models, we show that the linear and circular polarization structure can be successfully approximated with relatively few model parameters. We then fit this model to EHT observations of M87* taken in 2017. In total intensity and linear polarization, the m-ring fits are consistent with previous results from imaging methods. In circular polarization, the m-ring fits indicate the presence of event-horizon-scale circular polarization structure, with a persistent dipolar asymmetry and orientation across several days. The same structure was recovered independently of observing band, used data products, and model assumptions. Despite this broad agreement, imaging methods do not produce similarly consistent results. Our circular polarization results, which imposed additional assumptions on the source structure, should thus be interpreted with some caution. Polarimetric geometric modeling provides a useful and powerful method to constrain the properties of horizon-scale polarized emission, particularly for sparse arrays like the EHT.
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| 3. |
- Prather, Ben, et al.
(författare)
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Comparison of Polarized Radiative Transfer Codes Used by the EHT Collaboration
- 2023
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 950:1
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Tidskriftsartikel (refereegranskat)abstract
- Interpretation of resolved polarized images of black holes by the Event Horizon Telescope (EHT) requires predictions of the polarized emission observable by an Earth-based instrument for a particular model of the black hole accretion system. Such predictions are generated by general relativistic radiative transfer (GRRT) codes, which integrate the equations of polarized radiative transfer in curved spacetime. A selection of ray-tracing GRRT codes used within the EHT Collaboration is evaluated for accuracy and consistency in producing a selection of test images, demonstrating that the various methods and implementations of radiative transfer calculations are highly consistent. When imaging an analytic accretion model, we find that all codes produce images similar within a pixel-wise normalized mean squared error (NMSE) of 0.012 in the worst case. When imaging a snapshot from a cell-based magnetohydrodynamic simulation, we find all test images to be similar within NMSEs of 0.02, 0.04, 0.04, and 0.12 in Stokes I, Q, U, and V, respectively. We additionally find the values of several image metrics relevant to published EHT results to be in agreement to much better precision than measurement uncertainties.
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| 4. |
- Torne, Pablo, et al.
(författare)
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A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set
- 2023
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 959:1
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Tidskriftsartikel (refereegranskat)abstract
- In 2017 the Event Horizon Telescope (EHT) observed the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz (lambda = 1.3 mm). The fundamental physics tests that even a single pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT data sets. The high observing frequency means that pulsars-which typically exhibit steep emission spectra-are expected to be very faint. However, it also negates pulse scattering, an effect that could hinder pulsar detections in the Galactic center. Additionally, magnetars or a secondary inverse Compton emission could be stronger at millimeter wavelengths than at lower frequencies. We present a search for pulsars close to Sgr A* using the data from the three most sensitive stations in the EHT 2017 campaign: the Atacama Large Millimeter/submillimeter Array, the Large Millimeter Telescope, and the IRAM 30 m Telescope. We apply three detection methods based on Fourier-domain analysis, the fast folding algorithm, and single-pulse searches targeting both pulsars and burst-like transient emission. We use the simultaneity of the observations to confirm potential candidates. No new pulsars or significant bursts were found. Being the first pulsar search ever carried out at such high radio frequencies, we detail our analysis methods and give a detailed estimation of the sensitivity of the search. We conclude that the EHT 2017 observations are only sensitive to a small fraction (less than or similar to 2.2%) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region.
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| 5. |
- Jorstad, S.G., et al.
(författare)
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The Event Horizon Telescope Image of the Quasar NRAO 530
- 2023
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 943:2
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Tidskriftsartikel (refereegranskat)abstract
- We report on the observations of the quasar NRAO 530 with the Event Horizon Telescope (EHT) on 2017 April 5-7, when NRAO 530 was used as a calibrator for the EHT observations of Sagittarius A*. At z = 0.902, this is the most distant object imaged by the EHT so far. We reconstruct the first images of the source at 230 GHz, at an unprecedented angular resolution of similar to 20 mu as, both in total intensity and in linear polarization (LP). We do not detect source variability, allowing us to represent the whole data set with static images. The images reveal a bright feature located on the southern end of the jet, which we associate with the core. The feature is linearly polarized, with a fractional polarization of similar to 5%-8%, and it has a substructure consisting of two components. Their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. The jet extends over 60 mu as along a position angle similar to -28 degrees. It includes two features with orthogonal directions of polarization (electric vector position angle), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet. The outermost feature has a particularly high degree of LP, suggestive of a nearly uniform magnetic field. Future EHT observations will probe the variability of the jet structure on microarcsecond scales, while simultaneous multiwavelength monitoring will provide insight into the high-energy emission origin.
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| 6. |
- Rutten, Martijn G. S., et al.
(författare)
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Normalization of hepatic ChREBP activity does not protect against liver disease progression in a mouse model for Glycogen Storage Disease type Ia
- 2023
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Ingår i: Cancer & Metabolism. - : Springer Nature. - 2049-3002. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundGlycogen storage disease type 1a (GSD Ia) is an inborn error of metabolism caused by a defect in glucose-6-phosphatase (G6PC1) activity, which induces severe hepatomegaly and increases the risk for liver cancer. Hepatic GSD Ia is characterized by constitutive activation of Carbohydrate Response Element Binding Protein (ChREBP), a glucose-sensitive transcription factor. Previously, we showed that ChREBP activation limits non-alcoholic fatty liver disease (NAFLD) in hepatic GSD Ia. As ChREBP has been proposed as a pro-oncogenic molecular switch that supports tumour progression, we hypothesized that ChREBP normalization protects against liver disease progression in hepatic GSD Ia.MethodsHepatocyte-specific G6pc knockout (L-G6pc−/−) mice were treated with AAV-shChREBP to normalize hepatic ChREBP activity.ResultsHepatic ChREBP normalization in GSD Ia mice induced dysplastic liver growth, massively increased hepatocyte size, and was associated with increased hepatic inflammation. Furthermore, nuclear levels of the oncoprotein Yes Associated Protein (YAP) were increased and its transcriptional targets were induced in ChREBP-normalized GSD Ia mice. Hepatic ChREBP normalization furthermore induced DNA damage and mitotic activity in GSD Ia mice, while gene signatures of chromosomal instability, the cytosolic DNA-sensing cGAS-STING pathway, senescence, and hepatocyte dedifferentiation emerged.ConclusionsIn conclusion, our findings indicate that ChREBP activity limits hepatomegaly while decelerating liver disease progression and protecting against chromosomal instability in hepatic GSD Ia. These results disqualify ChREBP as a therapeutic target for treatment of liver disease in GSD Ia. In addition, they underline the importance of establishing the context-specific roles of hepatic ChREBP to define its therapeutic potential to prevent or treat advanced liver disease.
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| 7. |
- Salganik, E., et al.
(författare)
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Temporal evolution of under-ice meltwater layers and false bottoms and their impact on summer Arctic sea ice mass balance
- 2023
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Ingår i: Elementa: Science of the Anthropocene. - 2325-1026. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Low-salinity meltwater from Arctic sea ice and its snow cover accumulates and creates under-ice meltwater layers below sea ice. These meltwater layers can result in the formation of new ice layers, or false bottoms, at the interface of this low-salinity meltwater and colder seawater. As part of the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC), we used a combination of sea ice coring, temperature profiles from thermistor strings and underwater multibeam sonar surveys with a remotely operated vehicle (ROV) to study the areal coverage and temporal evolution of under-ice meltwater layers and false bottoms during the summer melt season from mid-June until late July. ROV surveys indicated that the areal coverage of false bottoms for a part of the MOSAiC Central Observatory (350 by 200 m2) was 21%. Presence of false bottoms reduced bottom ice melt by 7-8% due to the local decrease in the ocean heat flux, which can be described by a thermodynamic model. Under-ice meltwater layer thickness was larger below first-year ice and thinner below thicker second-year ice. We also found that thick ice and ridge keels confined the areas in which under-ice meltwater accumulated, preventing its mixing with underlying seawater. While a thermodynamic model could reproduce false bottom growth and melt, it could not describe the observed bottom melt rates of the ice above false bottoms. We also show that the evolution of under-ice meltwaterlayer salinity below first-year ice is linked to brine flushing from the above sea ice and accumulating in the meltwater layer above the false bottom. The results of this study aid in estimating the contribution of underice meltwater layers and false bottoms to the mass balance and salt budget for Arctic summer sea ice.
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| 8. |
- Senanayake, Indunil C., et al.
(författare)
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Fungal diversity notes 1611–1716: taxonomic and phylogenetic contributions on fungal genera and species emphasis in south China
- 2023
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Ingår i: Fungal Diversity. - 1560-2745 .- 1878-9129. ; 122, s. 161-403
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Tidskriftsartikel (refereegranskat)abstract
- This article is the 15th contribution in the Fungal Diversity Notes series, wherein 115 taxa from three phyla, nine classes, 28 orders, 48 families, and 64 genera are treated. Fungal taxa described and illustrated in the present study include a new family, five new genera, 61 new species, five new combinations, one synonym, one new variety and 31 records on new hosts or new geographical distributions. Ageratinicolaceae fam. nov. is introduced and accommodated in Pleosporales. The new genera introduced in this study are Ageratinicola, Kevinia, Pseudomultiseptospora (Parabambusicolaceae), Marasmiellomycena, and Vizzinia (Porotheleaceae). Newly described species are Abrothallus altoandinus, Ageratinicola kunmingensis, Allocryptovalsa aceris, Allophoma yuccae, Apiospora cannae, A. elliptica, A. pallidesporae, Boeremia wisteriae, Calycina papaeana, Clypeococcum lichenostigmoides, Coniochaeta riskali-shoyakubovii, Cryphonectria kunmingensis, Diaporthe angustiapiculata, D. campylandrae, D. longipapillata, Diatrypella guangdongense, Dothiorella franceschinii, Endocalyx phoenicis, Epicoccum terminosporum, Fulvifomes karaiensis, F. pannaensis, Ganoderma ghatensis, Hysterobrevium baoshanense, Inocybe avellaneorosea, I. lucida, Jahnula oblonga, Kevinia lignicola, Kirschsteiniothelia guangdongensis, Laboulbenia caprina, L. clavulata, L. cobiae, L. cosmodisci, L. nilotica, L. omalii, L. robusta, L. similis, L. stigmatophora, Laccaria rubriporus, Lasiodiplodia morindae, Lyophyllum agnijum, Marasmiellomycena pseudoomphaliiformis, Melomastia beihaiensis, Nemania guangdongensis, Nigrograna thailandica, Nigrospora ficuum, Oxydothis chinensis, O. yunnanensis, Petriella thailandica, Phaeoacremonium chinensis, Phialocephala chinensis, Phytophthora debattistii, Polyplosphaeria nigrospora, Pronectria loweniae, Seriascoma acutispora, Setoseptoria bambusae, Stictis anomianthi, Tarzetta tibetensis, Tarzetta urceolata, Tetraploa obpyriformis, Trichoglossum beninense, and Tricoderma pyrrosiae. We provide an emendation for Urnula ailaoshanensis Agaricus duplocingulatoides var. brevisporus introduced as a new variety based on morphology and phylogeny.
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| 9. |
- Buchanan, Christy M., et al.
(författare)
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Developmental Trajectories of Parental Self-Efficacy as Children Transition to Adolescence in Nine Countries : Latent Growth Curve Analyses
- 2023
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Ingår i: Journal of Youth and Adolescence. - : Plenum Publishing. - 0047-2891 .- 1573-6601. ; 53, s. 1047-1065
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about the developmental trajectories of parental self-efficacy as children transition into adolescence. This study examined parental self-efficacy among mothers and fathers over 3 1/2 years representing this transition, and whether the level and developmental trajectory of parental self-efficacy varied by cultural group. Data were drawn from three waves of the Parenting Across Cultures (PAC) project, a large-scale longitudinal, cross-cultural study, and included 1178 mothers and 1041 fathers of children who averaged 9.72 years of age at T1 (51.2% girls). Parents were from nine countries (12 ethnic/cultural groups), which were categorized into those with a predominant collectivistic (i.e., China, Kenya, Philippines, Thailand, Colombia, and Jordan) or individualistic (i.e., Italy, Sweden, and USA) cultural orientation based on Hofstede's Individualism Index (Hofstede Insights, 2021). Latent growth curve analyses supported the hypothesis that parental self-efficacy would decline as children transition into adolescence only for parents from more individualistic countries; parental self-efficacy increased over the same years among parents from more collectivistic countries. Secondary exploratory analyses showed that some demographic characteristics predicted the level and trajectory of parental self-efficacy differently for parents in more individualistic and more collectivistic countries. Results suggest that declines in parental self-efficacy documented in previous research are culturally influenced.
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| 10. |
- He, Yibo, et al.
(författare)
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A subset of antibodies targeting citrullinated proteins confers protection from rheumatoid arthritis.
- 2023
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Although elevated levels of anti-citrullinated protein antibodies (ACPAs) are a hallmark of rheumatoid arthritis (RA), the in vivo functions of these antibodies remain unclear. Here, we have expressed monoclonal ACPAs derived from patients with RA, and analyzed their functions in mice, as well as their specificities. None of the ACPAs showed arthritogenicity nor induced pain-associated behavior in mice. However, one of the antibodies, clone E4, protected mice from antibody-induced arthritis. E4 showed a binding pattern restricted to skin, macrophages and dendritic cells in lymphoid tissue, and cartilage derived from mouse and human arthritic joints. Proteomic analysis confirmed that E4 strongly binds to macrophages and certainRA synovial fluid proteins such as α-enolase. The protective effect of E4 was epitope-specific and dependent on the interaction between E4-citrullinated α-enolase immune complexes with FCGR2B on macrophages, resulting in increased IL-10 secretion and reduced osteoclastogenesis. These findings suggest that a subset of ACPAs have therapeutic potential in RA.
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