Hasil untuk "gr-qc"

A. Acharyya, A. Archer, P. Bangale et al.

In 2017 September, a high-energy neutrino event detected by the IceCube Neutrino Observatory (IceCube-170922A) was associated, at the 3 σ level, with a gamma-ray flare from the blazar TXS 0506+056. Cosmic rays that are accelerated in astrophysical sources can escape from their jets and interact with background radiation fields. Interactions with the extragalactic background light can produce pions and hence neutrinos, while interactions with the cosmic microwave background predominantly drive inverse Compton scattering, contributing to electromagnetic cascades in intergalactic space. The resulting secondary gamma-ray emission can be detected with high-energy gamma-ray telescopes. Here, we report on a new search for such cosmogenic cascade emission from the blazar TXS 0506+056, using a combined data set from the Fermi Large Area Telescope and VERITAS. We compare the gamma-ray spectrum and neutrino observations with the predictions of cosmic-ray-induced cascades in intergalactic space. The observed gamma-ray spectrum is modeled as a combination of the primary spectrum and the cascade spectrum. We apply a Monte Carlo simulation with a Δ χ ^2 -based likelihood analysis to jointly determine the best-fit parameters of a proton emission spectrum describing the data and derive constraints on the proton escape luminosity. Assuming an LP primary photon spectrum, we find consistency with a proton injection spectral index of α _p  ≃ 2.0 and a cutoff energy of E _p,max  ≃ 1.3 × 10 ^16 eV and constrain the isotropic proton escape luminosity to 1 × 10 ^44 erg s ^−1 ≲ L _p,esc  ≲ 3 × 10 ^45 erg s ^−1 at the 90% confidence level.

Guardiola Esther Natalia, Sumitro Sutiman Bambang, Widyarti Sri

It is well known that bitter gourd and noni fruit contain high levels of beneficial chemicals, but tastes and flavour are less appealing. Due to enzymatic transformation, fermentation can change bioactive compounds that minimize bad taste and unpleasant odor. This study aimed to assess the phenol and flavonoid content and antioxidant activity of bitter gourd (Momordica charantia L.) and noni fruit (Morinda citrifolia) during fermentation in honey. Blendered-bitter gourd (BG) or noni fruit (NF) each is mixed with honey and distilled water in a ratio of 3:1:10, then fermented for 90 days at room temperature and anaerobic conditions. Total phenol (TPC), total flavonoid content (TFC), and antioxidant activity were measured every two weeks. TPC in fermented NF increased from 56.62 mg GAE/gr to 156.59 GAE in the 6-week. TPC in BG increased from 56.96 GAE/g to 146.39 GAE/g during 12-week fermentation. TFC of fermented NF increased from 4.55 mg QC/g to 12.92 mg QC/g in 12-week fermentation. TFC of fermented BG increased from 9.86 QC/g to 41.69 QC/g in 12 weeks of fermentation. The antioxidant activity of fermented BM and BP showed the highest antioxidant activity in the 6-week (0,574 mg TEAC/g and 0.528 mg TEAC/g). The results indicate that fermentation in honey can increase total phenol and flavonoid content, and the antioxidant activity of bitter gourd and noni fruit.

B. C. Lütfüoğlu

Abstract We calculate quasinormal modes and gray-body factors of a massive scalar field in the background of three compact objects in the Weyl gravity: Schwarzschild-like back holes, known as Mannheim–Kazanas solution, non-Schwrazschild-like black holes and traversable wormholes found recently in (Jizba and Mudruňka in Phys Rev D 110(12):124006, 2024, https://doi.org/10.1103/PhysRevD.110.124006 , arXiv:2409.08344 [gr-qc]). We show that the spectrum of the massive field is qualitatively different from massless o ne both in the frequency and time domains. While the mass term leads to much longer lifetime of the modes, the arbitrarily long-lived modes, known as quasi-resonances, are not achieved.

S. V. Bolokhov

Abstract Two models for Schwarzschild-like black holes with quantum corrections, derived from the Hamiltonian constraints approach to quantum gravity while preserving general covariance, have been developed in Zhang et al. (Phys. Rev. D 111, L081504, 2025, arXiv:2407.10168 [gr-qc]). In this work, we study the quasinormal modes of a massive scalar field and demonstrate that the spectrum includes arbitrarily long-lived modes, known as quasi-resonances. Precise calculations using the Leaver method show good agreement with WKB data and time-domain integration within the range where these methods are reliable, specifically for small field masses.

Deborah Neyrinck-Leglantier, Deborah Neyrinck-Leglantier, Deborah Neyrinck-Leglantier et al.

IntroductionPeople living with HIV (PLWH) now benefit from combined antiviral treatments that durably control viral replication. These antiretroviral treatments decrease mortality and improve quality of life in PLWH, but do not completely control the excessive non-specific activation of the immune system in PLWH. This chronic immune activation is a key element of HIV immunopathology that contributes to the pathophysiology of inflammatory comorbid conditions, such as cardiovascular disorders, cancer and autoimmune diseases. Circulating non-exosomal extracellular vesicles, also known as microparticles (MPs) are detected in these diseases and have been linked to immune activation. The objective of this study was to characterize the MPs present in PLWH and to assess their association with chronic immune activation.MethodsWe performed flow cytometry for the complete phenotypic characterization of MPs from fresh plasma from PLWH and from people without HIV as the control group. The absolute number, size and cellular origin of MPs were evaluated. The immunoregulatory profile was determined by cell origin, for MPs derived from platelets (PMPs), monocytes (MMPs) and T lymphocytes (LMPs).ResultsPLWH had significantly more circulating MPs than controls, for MPs of all sizes originating from T lymphocytes, red blood cells, neutrophils, dendritic cells, B lymphocytes and endothelial cells. PMPs and MMPs were not more numerous in PLWH, but the immunoregulatory phenotypes of these MPs differed between PLWH and controls. These differences in immunoregulatory molecule expression profile were also observed for LMPs. PDL1, ICOSL, CCR5, TGFβ1, MHC classes I and II, TRAIL, CXCR4, OX40, DC-SIGN, CTLA4 and PDL2 were more strongly expressed on the surface of MPs from PLWH than on those from controls.ConclusionMPs are an important element in intercellular communication, making it possible to transfer phenotypes and functions to immune cells. The significantly higher numbers of MPs expressing diverse immunomodulatory molecules in PLWH may make a major contribution to the maintenance and/or the development of immune-cell activation in these individuals.

Katie A. Crotts, Brenda C. Matthews, Gaspard Duchêne et al.

The Gemini Planet Imager (GPI) has excelled in imaging debris disks in the near-infrared. The GPI Exoplanet Survey imaged 24 debris disks in polarized H -band light, while other programs observed half of these disks in polarized J and/or K 1 bands. Using these data, we present a uniform analysis of the morphology of each disk to find asymmetries suggestive of perturbations, particularly those due to planet–disk interactions. The multiwavelength surface brightness, disk color, and geometry permit the identification of any asymmetries such as warps or disk offsets from the central star. We find that 19 of the disks in this sample exhibit asymmetries in surface brightness, disk color, disk geometry, or a combination of the three, suggesting that for this sample, perturbations, as seen in scattered light, are common. The relationship between these perturbations and potential planets in the system is discussed. We also explore correlations among stellar temperatures, ages, disk properties, and observed perturbations. We find significant trends between the vertical aspect ratio and the stellar temperature, disk radial extent, and the dust grain size distribution power law, q . We also confirm a trend between the disk color and stellar effective temperature, where the disk becomes increasingly red/neutral with increasing temperature. Such results have important implications for the evolution of debris disk systems around stars of various spectral types.

Stella Yimiao Zhang, Gaspard Duchêne, Robert J. De Rosa et al.

The HR 2562 system is a rare case where a brown dwarf companion resides in a cleared inner hole of a debris disk, offering invaluable opportunities to study the dynamical interaction between a substellar companion and a dusty disk. We present the first ALMA observation of the system as well as the continued Gemini Planet Imager monitoring of the companion’s orbit with six new epochs from 2016 to 2018. We update the orbital fit, and in combination with absolute astrometry from GAIA, place a 3 σ upper limit of 18.5 M _J on the companion’s mass. To interpret the ALMA observations, we used radiative transfer modeling to determine the disk properties. We find that the disk is well resolved and nearly edge-on. While the misalignment angle between the disk and the orbit is weakly constrained, due to the short orbital arc available, the data strongly support a (near) coplanar geometry for the system. Furthermore, we find that the models that describe the ALMA data best have inner radii that are close to the companion’s semimajor axis. Including a posteriori knowledge of the system’s SED further narrows the constraints on the disk’s inner radius and places it at a location that is in reasonable agreement with (possibly interior to) predictions from existing dynamical models of disk truncation by an interior substellar companion. HR 2562 has the potential over the next few years to become a new test bed for dynamical interaction between a debris disk and a substellar companion.

A. Di Teodoro, E. Contreras

Abstract In this work, we construct a modified version of the Einstein field equations for a vacuum and spherically symmetric spacetime in terms of the Riemann–Liouville fractional derivative. The main difference between our approach and other works is that we ensure that both the classical differential equations and the classical solutions are exactly recovered in the limit when the fractional parameter is turned off. We assume that the fractional equations are valid inside and near the horizon radius and match the classical solution at the horizon. Our approach resembles the Herrera–Witten strategy (Adv High Energy Phys 2018:3839103, 2018, https://doi.org/10.1155/2018/3839103 , arXiv:1806.07143 [gr-qc]), where the authors constructed an alternative black hole solution by assuming that inside the horizon the spacetime is hyperbolically symmetric and matches the classical spherically symmetric exterior solution at one point at the horizon. We obtain that, depending on the value of the fractional parameter, the solutions can be interpreted as a regular black hole or a gravastar. As a final step, we compute the fractional curvature scalars and show that the solution is regular everywhere inside the horizon.

Shreejit Jadhav, Mihir Shrivastava, Sanjit Mitra

The ability of deep learning (DL) approaches to learn generalised signal and noise models, coupled with their fast inference on GPUs, holds great promise for enhancing gravitational-wave (GW) searches in terms of speed, parameter space coverage, and search sensitivity. However, the opaque nature of DL models severely harms their reliability. In this work, we meticulously develop a DL model stage-wise and work towards improving its robustness and reliability. First, we address the problems in maintaining the purity of training data by deriving a new metric that better reflects the visual strength of the ‘chirp’ signal features in the data. Using a reduced, smooth representation obtained through a variational auto-encoder (VAE), we build a classifier to search for compact binary coalescence (CBC) signals. Our tests on real LIGO data show an impressive performance of the model. However, upon probing the robustness of the model through adversarial attacks, its simple failure modes were identified, underlining how such models can still be highly fragile. As a first step towards bringing robustness, we retrain the model in a novel framework involving a generative adversarial network (GAN). Over the course of training, the model learns to eliminate the primary modes of failure identified by the adversaries. Although absolute robustness is practically impossible to achieve, we demonstrate some fundamental improvements earned through such training, like sparseness and reduced degeneracy in the extracted features at different layers inside the model. We show that these gains are achieved at practically zero loss in terms of model performance on real LIGO data before and after GAN training. Through a direct search on ${\sim}8.8$ days of LIGO data, we recover two significant CBC events from GWTC-2.1 (Abbott et al 2022 https://arxiv.org/abs/2108.01045 [gr-qc]), GW190519_153544 and GW190521_074359. We also report the search sensitivity obtained from an injection study.

Saeid Ebrahimi, Vahid Kamali, Asma Alaei

Abstract High dissipative regime of warm pseudoscalar inflation model (Kamali in Phys Rev D 100:043520, arXiv:1901.01897 [gr-qc], 2019) with an approximately constant value of dissipation parameter Q is studied. Intermediate solution of the scale-factor related to the accelerated expansion of the Universe which is rolled out by observational data in the context of standard (cold) model of inflation is used. There is a region of free parameters phase-space of the model which is interestingly compatible with recent observational data. It is discussed that the model is also compatible with the swampland criteria in a broad range of parameters phase-space and TCC in a limited area of parameters.

The Event Horizon Telescope Collaboration, Kazunori Akiyama, Juan Carlos Algaba et al.

In 2017 April, the Event Horizon Telescope (EHT) observed the near-horizon region around the supermassive black hole at the core of the M87 galaxy. These 1.3 mm wavelength observations revealed a compact asymmetric ring-like source morphology. This structure originates from synchrotron emission produced by relativistic plasma located in the immediate vicinity of the black hole. Here we present the corresponding linear-polarimetric EHT images of the center of M87. We find that only a part of the ring is significantly polarized. The resolved fractional linear polarization has a maximum located in the southwest part of the ring, where it rises to the level of ∼15%. The polarization position angles are arranged in a nearly azimuthal pattern. We perform quantitative measurements of relevant polarimetric properties of the compact emission and find evidence for the temporal evolution of the polarized source structure over one week of EHT observations. The details of the polarimetric data reduction and calibration methodology are provided. We carry out the data analysis using multiple independent imaging and modeling techniques, each of which is validated against a suite of synthetic data sets. The gross polarimetric structure and its apparent evolution with time are insensitive to the method used to reconstruct the image. These polarimetric images carry information about the structure of the magnetic fields responsible for the synchrotron emission. Their physical interpretation is discussed in an accompanying publication.

The Event Horizon Telescope Collaboration, Kazunori Akiyama, Juan Carlos Algaba et al.

Event Horizon Telescope (EHT) observations at 230 GHz have now imaged polarized emission around the supermassive black hole in M87 on event-horizon scales. This polarized synchrotron radiation probes the structure of magnetic fields and the plasma properties near the black hole. Here we compare the resolved polarization structure observed by the EHT, along with simultaneous unresolved observations with the Atacama Large Millimeter/submillimeter Array, to expectations from theoretical models. The low fractional linear polarization in the resolved image suggests that the polarization is scrambled on scales smaller than the EHT beam, which we attribute to Faraday rotation internal to the emission region. We estimate the average density n _e ∼ 10 ^4–7 cm ^−3 , magnetic field strength B ∼ 1–30 G, and electron temperature T _e ∼ (1–12) × 10 ^10 K of the radiating plasma in a simple one-zone emission model. We show that the net azimuthal linear polarization pattern may result from organized, poloidal magnetic fields in the emission region. In a quantitative comparison with a large library of simulated polarimetric images from general relativistic magnetohydrodynamic (GRMHD) simulations, we identify a subset of physical models that can explain critical features of the polarimetric EHT observations while producing a relativistic jet of sufficient power. The consistent GRMHD models are all of magnetically arrested accretion disks, where near-horizon magnetic fields are dynamically important. We use the models to infer a mass accretion rate onto the black hole in M87 of (3–20) × 10 ^−4 M _⊙ yr ^−1 .

Gagnon S, Saab M

Steven Gagnon,1– 3 Marc Saab1,2,4– 6 1Département d’ophtalmologie et d’oto-rhino-laryngologie – chirurgie cervico-faciale, Université Laval, Québec, QC, Canada; 2Hôpital Régional de Rimouski, Centre intégré de santé et de services sociaux du Bas-Saint-Laurent, Rimouski, QC, Canada; 3Centre Universitaire d’ophtalmologie (CUO), Hôpital du Saint-Sacrement, Québec, QC, Canada; 4Hôpital Charles-LeMoyne, Centre intégré de santé et de services sociaux de la Montérégie-Centre, Greenfield Park, QC, Canada; 5Service d’ophtalmologie, Université de Sherbrooke, Sherbrooke, QC, Canada; 6Département d’ophtalmologie, Université de Montréal, Montréal, QC, CanadaCorrespondence: Steven Gagnon 1083, rue du Chevreau, Lévis, QC G6Z 3C3, CanadaEmail gagn0n@hotmail.comPurpose: Endogenous endophthalmitis is uncommon but potentially dangerous. We present a fatal presentation of endogenous Nocardial endophthalmitis in the context of steroid use for treatment of giant cell arteritis.Case Presentation: An 84-year-old Caucasian female presented to the local emergency room with severe headaches, myalgia and shoulder and calf muscle pain. She was treated for a presumed diagnosis of giant-cell arteritis with corticosteroids and subsequently developed an intense retro-orbital pain in the right eye. Fundus examination revealed a white, vascularized chorioretinal mass at the equator of the eye in the inferotemporal quadrant. Antibiotics were given and a vitrectomy was performed. The culture of the vitreous showed Nocardia nova and a diagnosis of disseminated Nocardiosis was made.Conclusion and Significance: Although uncommon, it is important that ophthalmologists are aware of Nocardial infections as a differential diagnosis of retinal mass, particularly in immunocompromised patients.Keywords: Nocardiosis, systemic, Nocardia, eye, intraocular, endophthalmitis, endogenous

Sofia Kostopoulou, Georgia Ntatsi, Gerasimos Arapis et al.

The GC/EI/MS metabolite profiles of Lemna minor L. plants were recorded following treatments with sub-lethal concentrations of the herbicidal active ingredients (a.i.) metribuzin and glyphosate, and various of their binary mixtures. The raw GC/EI/MS total ion chromatograms (*.cdf format) of the Lemna's endo-metabolomes were recorded, which are included in this article. Since Lemna is a model organism in ecotoxicological studies, the dataset could serve as a reference for Lemna metabolomics studies related to the investigation of the effects of phytotoxic compounds and their mixtures on its metabolism. Also, the dataset could be a valuable resource for the discovery of validated biomarkers of the toxicity of mixtures. The dataset support the research article “Kostopoulou et al., Assessment of the effects of metribuzin, glyphosate, and their mixtures on the metabolism of the model plant Lemna minor L. applying metabolomics. “Chemosphere 239, 2020, 124582.” Keywords: Combined toxicity, Ecotoxicogenomics, Phytotoxicity, Lemna metabolomics

Chenel V, Mortenson WB, Guay M et al.

Vanessa Chenel,1,2 W Ben Mortenson,3–5 Manon Guay,6,7 Jeffrey William Jutai,8,9 Claudine Auger1,2 1School of Rehabilitation, Faculty of Medicine, Université de Montréal, 2Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR) – Institut universitaire sur la réadaptation en déficience physique de Montréal, Centre intégré universitaire de santé et de services sociaux du Centre-Sud-de-l’Île-de-Montréal, Montreal, QC, 3Department of Occupational Science and Occupational Therapy, Faculty of Medicine, University of British Columbia, 4GF Strong Rehabilitation Centre, 5International Collaboration on Repair Discoveries, University of British Columbia, Vancouver Coastal Health Research Institute, Vancouver, BC, 6School of Rehabilitation, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 7Research Centre on Aging, Centre intégré universitaire de santé et de services sociaux de l’Estrie – Centre hospitalier universitaire de Sherbrooke, Sherbrooke, QC, 8Interdisciplinary School of Health Sciences, University of Ottawa, 9Bruyère Research Institute, Ottawa, ON, Canada Abstract: In order to promote self-determination, patients have to be actively involved with their care providers in health-care decision making, especially when such decisions involve personal preferences. Decision aids (DAs) are tools that can contribute to patient-centered decision-making processes. To benefit from previous fieldwork and avoid duplicating developmental efforts and producing many similar DAs, the adaptation of existing DAs to new cultural contexts is a resource-saving option. However, there are no guidelines on how to culturally adapt and validate DAs. This study aimed to identify and document existing procedures for the cultural adaptation and validation of patient DAs. A scoping review examined studies conducting cultural adaptation and/or validation of patient DAs. The following databases were searched in February 2016: CINAHL, EMBASE, Medline (Ovid), PASCAL, PsychINFO, and PubMed. From the 13 studies selected, 11 main procedures were identified: appraisal of the original DA, assessment of the new cultural context, translation, linguistic adaptation, cultural adaptation, usability testing, exploration of DA acceptability, test-retest reliability, content validity, con­struct validity, and criterion validity. A conceptual synthesis of these studies suggests there are four phases in the adaptation/validation process of DAs aimed at: 1) exploring the original DA and the new cultural context, 2) adapting the original DA to the new cultural context, 3) lab testing the preliminary version of the adapted DA, and 4) field testing the adapted DA in a real use context. By facilitating the adaptation and broader implementation of DAs, patients may ultimately be empowered in decision-making processes. Keywords: decision making, decision support techniques, translation, cultural adaptation, validation studies

T. Jacobson

I. Kanatchikov

D. Giulini

G. Gibbons, C. Wells