Search Results (1,148)

Despite several efforts to investigate the accretion disk and torus, near-simultaneous broadband studies of the nuclear regions of radio-quiet AGNs remain lacking. NGC 4151, one of the closest and brightest Seyfert galaxies, provides an excellent laboratory for probing the circum-nuclear regions of AGNs. A detailed, near-simultaneous broadband spectral study of NGC 4151 is carried out during one of its historic minimum activity states, using archival data from the Ultraviolet (UV) to the Infrared (IR) regions. We used the radiative transfer code SKIRT to model the source and to constrain the properties of the torus. We found that the observed broadband spectral energy distribution is best explained by a two-torus geometry with a polar conical shell structure. Full article

The basement of the Rattlesnake Creek terrane (RCT) in the Klamath Mountains is a mélange of metamorphosed sedimentary and igneous blocks. Recent work shows that the overlying RCT cover sequence has a North American provenance but formed after accretion to the continental margin, so it is unclear if the basement mélange formed exotic or endemic to North America. This study presents petrography and zircon geochronology from RCT metasedimentary blocks and crosscutting intrusions. The southernmost RCT preserves both Early Jurassic and Middle-Late Jurassic cover sequence deposits and records continental clasts and 33% pre-Mesozoic zircons at ~201 Ma, effectively none at ~191 Ma, and 79–90% from 168 to 163 Ma. During active magmatism 207–193 Ma, the RCT was receiving continental sediment, inconsistent with a distant intraoceanic arc. We interpret that the RCT subduction zone formed proximal to North America in the Late Triassic and that there was a sediment pathway to the RCT at ~201 Ma. During Middle to Late Jurassic rifting and subsequent Nevadan compression, the cover sequences were dismembered and incorporated into the mélange by tectonic and sedimentary processes. The age and provenance of metasedimentary deposits in the RCT is inconsistent with west-dipping subduction models in the Klamath Mountains region. Full article

Morphological variability on Mediterranean embayed sandy beaches is largely driven by wave storms and episodic sediment inputs from local streams during intense rainfall. While storm impacts are well documented, the combined influence of stream discharge, wave forcing and morphological response remains poorly understood. This study examines these interactions at Castell beach, one of the few non-urbanised, stream-fed embayed beaches on the northwestern Mediterranean, during two high-energy storms with heavy rainfall: December 2019 and January 2020 (Storm Gloria). Morphological changes in the subaerial and submerged beach, and stream dynamics were assessed using repeated RTK–GNSS surveys, orthophotos and echo-sounder bathymetry. Results show the stream mouth shifted along the beach (east, central or west) during heavy rainfall episodes depending on wave direction and pre-existing topography, tending toward more wave-sheltered zones. The storms induced contrasting responses: the first caused slight subaerial accretion, whereas Storm Gloria produced subaerial erosion and nearshore sediment deposition from both beach and stream sources. This material was subsequently reworked and reincorporated into the subaerial beach under calmer conditions, with full recovery by February 2022. These findings highlight the role of stream–wave interactions in sediment dynamics and the capacity of highly protected embayed beaches to adapt to extreme events. Full article

Double-double radio galaxies (DDRGs) display inner and outer jets or lobes thought to result from intermittent accretion. Due to randomly triggered accretion events, the lifetime of the retriggered jet is not expected to have any connection to the time of quiescence between jets, yet we show that a correlation between the two quantities may exist, which we interpret as resulting from continued accretion through the quiescent jet phase. Despite continuous accretion, a jet is absent because its presence depends on a non-zero value of black hole spin, but accretion transitions the system from counter-rotation to corotation, and therefore through zero black hole spin where a jet cannot form. The time of jet quiescence depends on how long it takes to spin the black hole up again in corotation, which is longer for lower accretion rates. Once the black hole spin is large enough for a renewed jet, this inner jet will last longer the lower the accretion rate is. Hence, in a continuous accretion scenario, longer quiescent times tend to associate to longer inner jet times. In addition, DDRG jets are of FRII morphology which we show to result from the absence of a tilt in the accretion disk in the transition through zero black hole spin, ensuring the absence of an FRI jet in a way that connects with our understanding of X-shaped radio galaxies. Both correlated timescales as well as sameness in jet morphology offers evidence in favor of our picture. Full article

The mangrove ecosystems in Muara Angke, Jakarta, serve as a national benchmark for sustainable mangrove management in Indonesia, yet face significant urban pressures threatening their long-term viability. This study evaluates the ecological integrity and governance effectiveness of this critical ecosystem, covering Wildlife Reserve, Nature Park, Protected Forest, and Production Forest areas totaling 327.7 hectares. An exploratory mixed-methods approach was employed over four months (June–September 2025), integrating vegetation diversity assessments through plot sampling, avifauna surveys via point count methods, herpetofauna identification using Visual Encounter Surveys, water quality assessments through systematic literature review, geospatial analysis of mangrove dynamics using Sentinel-2A imagery (2015–2025), and social-governance evaluation using close-ended questionnaires and One Score One Criteria Scoring System. Results revealed moderate to severe water pollution with phosphate and nitrate exceeding standards, moderate vegetation diversity (13 species; Shannon-Wiener H′ = 1.466–1.728), high avifaunal diversity (55 species; H′ = 3.54) confirming significance along the East Asian-Australasian Flyway, and significant sediment accretion (32 hectares) attributed to coastal reclamation. Management evaluation identified critical conservation compliance deficiencies (score 1.43/7). The findings indicate urgent need for integrated interventions including pollution control, ecosystem-based restoration, enhanced monitoring, and cross-sector policy integration to prevent rapid mangrove degradation and ensure sustainability of this ecologically significant urban mangrove ecosystem. Full article

We investigate the thin accretion disk around Bardeen black hole (BH) surrounded by perfect fluid dark matter (PFDM), focusing on how the magnetic charge g and dark matter (DM) parameter b affect its radiative properties. The results show that increasing g slightly enhances the energy flux, radiation temperature, luminosity, and efficiency, while shifting the innermost stable circular orbit ($r_{\mathrm{isco}}$) inward. Additionally, the influence of b is found to be dominant, making it a key parameter in distinguishing PFDM-surrounded Bardeen BH from their Schwarzschild counterparts. Full article

Accreting neutron stars exhibit pulsed X-rays and complex temporal variability across multi-wavelengths and different timescales. This variability could be driven by various physical processes including instability or inhomogeneous motions within the accretion flow, thermonuclear bursts on the neutron star surface. In this review, we present a concise overview of the observational features for millihertz (mHz) quasi-periodic oscillations (QPOs) at a frequency range of ∼1–1000 mHz observed in light curves of X-ray pulsars for both low-mass X-ray binaries and high-mass X-ray binaries, based on recent X-ray missions, e.g., NICER, Insight-HXMT and NuSTAR. We further summarize current theoretical interpretations, discuss remaining challenges and propose potential directions for future studies to advance the understanding of the nature and physical origin of these QPOs. Full article

During late December 2021, an ice accretion disaster occurred in North Xinjiang, especially in the western part. It is found that the meteorological conditions suitable for the occurrence of ice accretion disasters are when the temperature is between −14 °C and −3 °C, the relative humidity is greater than 80%, the wind speed is between 4.5 m s⁻¹ and 7.5 m s⁻¹, and the pressure is between 919 hPa and 928 hPa. The ice accretion disaster is influenced by large-scale circulation, including the two-trough and one-ridge geopotential height structure in the middle troposphere and the spatially moving Ural Mountain blocking high pressure. Furthermore, using the artificial intelligence-based Pangu model and machine learning algorithms within the application of multiple linear regression and the leave-ten-out cross-validation, a skillful forecast correction model for ice accretion thickness in North Xinjiang is constructed. The prediction model has significant prediction skill for ice accretion thickness in North Xinjiang with 24 h, 48 h, and even 72 h in advance. The findings of the study can improve the timeliness of business system in the short-term and immediate forecast of ice accretion thickness, providing more reliable technical support for the ice prevention and disaster reduction of the power grids. Full article

Anti-icing materials have attracted considerable research interest due to their potential applications in preventing ice accretion and growth. However, a major challenge in the field is how to enhance durability while maintaining anti-icing performance. This study proposes a facile fabrication method for anti-icing coatings with anti-aging and self-healing abilities. A three-dimensionally cross-linked block copolymer, synthesized from polydimethylsiloxane, 4-aminophenyl disulfide, and trimethylolpropane triglycidyl ether, yielded a coating with excellent anti-icing/de-icing performance, including a low ice adhesion strength (29.2 kPa) and a high icing delay time (1389 s). The introduction of 4-aminophenyl disulfide enables dynamic disulfide bond reorganization and aromatic framework formation, synergistically conferring the icephobic coating with self-repair mechanisms and an anti-aging function. The coating exhibited a rapid self-healing capability (within 4 h), which is facilitated by the dynamic exchange of its hydrogen and disulfide bonds. Furthermore, the material demonstrated outstanding durability against physical wear and ultraviolet radiation. After being subjected to a 1000-cycle abrasion test and ultraviolet aging, the coating successfully retained more than 70% of its original performance in both icing delay time and ice adhesion strength. This paper proposes a facile strategy for developing self-healing and anti-aging anti-icing coatings and proposes innovative strategies for multifunctional anti-icing coatings. Full article

Goat meat is widely valued as a healthy option due to its lean nature, yet strategies to further optimize its intrinsic nutritional composition remain a key objective. This study examined the influence of melatonin on muscle development and visceral fat deposition in cashmere goats, focusing on its role in augmenting systemic antioxidant capacity and modifying gut microbiota. Thirty goat kids were randomly assigned to a control or a melatonin-treated (2 mg/kg body weight) group. Melatonin implantation induced a metabolic shift characterized by reduced visceral fat deposition (perirenal, omental, and mesenteric fat; p < 0.05) without impacting intramuscular fat. Concurrently, it promoted muscle accretion, as demonstrated by an increase in crude protein content and hypertrophy of muscle fibers in the Longissimus thoracis et lumborum, Gluteus medius, and Biceps femoris muscles (p < 0.05). These effects were underpinned by an enhanced systemic antioxidant capacity (elevated CAT, GSH-Px, T-AOC, and reduced MDA; p < 0.05), changes in gut microbiota, and a concomitant improvement in gastrointestinal morphology, evidenced by increased rumen papilla length and intestinal villus height. Melatonin enriched beneficial genera (e.g., Succiniclasticum, Butyrivibrio, Akkermansia), which were significantly correlated with reduced adiposity and improved protein deposition. These improvements resulted from the concerted actions of an enhanced systemic antioxidant defense system and a beneficially modulated gut microbial community. This trial observed no effect on intramuscular fat deposition, suggesting that improving intramuscular fat may require a systematic fattening regimen. This study provides a scientific foundation for employing melatonin as a nutritional strategy in goat production to improve meat quality. Full article

The James Webb Space Telescope (JWST) has begun to revolutionize our view of the Cosmos. The discovery of Blue Monsters (i.e., ultra-compact yet very bright high-z galaxies) and the Little Red Dots (i.e., very compact dustless strong Balmer break cosmic dawn sources) pose significant challenges to pre-JWST era models of the assembly of first stars and galaxies. In addition, JWST data further strengthen the problem posed by the origin of the supermassive black holes that power the most distant quasars observed. Stars powered by Dark Matter annihilation (i.e., Dark Stars) can form out of primordial gas clouds during the cosmic dawn era and subsequently might grow via accretion and become supermassive. In this paper we argue that Supermassive Dark Stars (SMDSs) offer natural solutions to the three puzzles mentioned above. Full article

Beach nourishment is a widely used strategy to mitigate coastal erosion, yet its long-term geological impacts remain poorly understood. This study provides a multi-decadal synthesis of shoreline change and sedimentological evolution on the nourished beaches of Cape May and Wildwood, New Jersey, USA. Using shoreline positions from 1991 to 2024, we identify contrasting trajectories: Wildwood exhibits ‘persistent transition’ with severe northern erosion (EPR: −10.0 m/yr) feeding southwards accretion, while Cape May demonstrates a ‘managed equilibrium’ with widespread accretion (mean EPR: +1.15 m/yr). Wave energy correlations account for less than 15% of shoreline variability, indicating natural drivers have been superseded by human sediment inputs. Direct sediment comparison shows substantial textural transformation, with median grain sizes increasing from 153 to 435 μm to 467–982 μm and sorting degrading from very well to moderately well sorted, reflecting sustained disequilibrium. These findings are synthesized into a conceptual model where nourishment initiates feedback cycles that create human-dependent morphodynamic trajectories. This study concludes that the long-term resilience of developed coasts will depend on a strategic evolution from managing ‘sand as volume’ toward stewarding ‘sediment as a system,’ where textural compatibility is a primary determinant of success. Full article

Pt-Fe alloys with abundant inclusions are from the Camumbi River placer deposit, Ecuador. They are derived from unknown Alaskan–Uralian-type intrusion(s) within the Late Cretaceous Naranjal accreted terrane. Compositions of our previously documented chilled silicate glass inclusions are increasingly fractioned from hydrous ferrobasalt to rhyolite in terms of TAS (total alkalis vs. silica). Their liquid lines of descent change from tholeiitic to the calc-alkaline magma series. Here, we document seven rare composite inclusion parageneses of Cu–PGM (platinum-group mineral) sulfides, each coexisting with and exsolved from related fractionated silicate glass (melt). Differentiation is dominated by fractional crystallization in PGM bulk compositions from tholeiitic silicate melts at the highest T (temperature): ~1018 °C. Silicate glass inclusions following the lower T calc-alkaline trend coexist with sulfide PGM parageneses that were likely differentiated, in terms of Pt-Rh-Pd and BMs (base metals), by incongruent melting due to decompression and S-degassing at ~983–830 °C. S-saturated sulfide melts become S-undersaturated below 845 °C. The calculated temperatures are for silicate glass. Pt-rich braggite shows increasing fractionation towards Pd-rich vysotskite within one inclusion paragenesis. A late braggite–vysotskite fractionation trend shows decreasing minor base metals (BMs). Thiospinels are dominated by cuprorhodsite. Minor thiospinels indicate Fe and then strong Ni enrichment at the lowest T. Decompression exsolutions, deflation, and the partial melting of some sulfide inclusion parageneses support rapid ascent to higher crustal levels within a deep-sourced cumulate intrusion. Full article

We review some aspects of accretion disks physics, spacetime photon shell and photon orbits, related to retrograde (counter-rotating) motion in Kerr black hole (BH) spacetimes. In this brief review, we examine the counter-rotating components of the Kerr BH shadow boundary, under the influence of counter-rotating accretion tori, accreting flows and proto-jets (open critical funnels of matter, associated with the tori) orbiting around the central BH. We also analyze the redshifted emission arising from counter-rotating structures. Regions of the shadows and photon shell are constrained in their dependence of the BH spin and observational angle. The effects of the counter-rotating structures on these are proven to be typical of the fast-spinning BHs, and accordingly can be observed only in the restricted classes of the Kerr BH spacetimes. This review is intended as a concise guide to the main properties of counter-rotating fluxes and counter-rotating disks in relation to the photon shell and the BH shadow boundary. Our findings may serve as the basis for different theoretical frameworks describing counter-rotating accretion flows with observable imprints manifesting at the BH shadow boundary. The results can eventually enable the distinction of counter-rotating fluxes through their observable imprints, contributing to constraints on both the BH spin and the structure of counter-rotating accretion disks. In particular, photon trajectories and their impact parameters can manifest in the morphology of the BH shadow. Such features, when accessible through high-resolution imaging and spectral or polarization measurements, could provide a direct avenue for testing different theoretical models on accretion disk dynamics and their BH attractors. Full article

The paper assesses brown seaweed diversity following the catastrophic events of the 2010 Deepwater Horizon (DWH) oil spill in offshore deep bank habitats at 45–90 m depth in the northwestern Gulf of Mexico, and their potential regeneration and recovery in the region. Innovative approaches to expeditionary and exploratory research resulted in the discovery, identification, and classification of brown seaweed diversity associated with rhodoliths (free-living carbonate nodules predominantly accreted by crustose coralline algae). Whereas the rhodoliths collected in situ at our research sites pre-DWH were teeming with brown algae growing on their surface, post-DWH they looked dead, bare, and bleached. These post-DWH impacts appear long-lasting, with little macroalgal growth recovery in the field. However, these apparent “dead” rhodoliths collected post-DWH at banks offshore Louisiana showed macroalgal regeneration starting within three weeks when placed in microcosms in the laboratory, with 19 brown algal species emerging from the bare rhodoliths’ surface. Some taxa corresponded to new records for the GMx (genus Cutleria and Dictyota cymatophila). Padina vickersiae is resurrected from synonymy with P. gymnospora. Reproductive sori evidence is presented for Lobophora declerckii. A detailed nomenclatural list, morphological plates, and phylogenetic/barcoding trees of brown seaweed that emerged from rhodoliths’ surfaces in laboratory microcosms are provided. These findings provide key molecular and morphological insights that reinforce species boundaries and highlight the significance of mesophotic rhodolith beds as previously overlooked reservoirs of cryptic brown algal diversity. Full article