Hasil untuk "Geophysics. Cosmic physics"

Xianliang Wu, Hong Li, Fanghua Xu

Abstract Oceanic mesoscale eddies are often asymmetric, exhibiting horizontal deformation and vertical tilt, yet the implications of these structural asymmetries for finer‐scale dynamics remain poorly understood. Based on a series of high‐resolution numerical experiments, we found that asymmetric anticyclones act as potent catalysts for submesoscale motions compared to symmetric counterparts. This catalysis follows a clear dynamical pathway. Initial asymmetries in elliptical and vertically tilting anticyclones rapidly develop vortex Rossby waves (VRWs) of azimuthal wavenumber‐2 and wavenumber‐1, respectively, through axisymmetrization. The breakdown of these VRWs generates small‐scale filaments, fronts and vortices along the periphery of the anticyclone, accompanied by strong strain and frontogenesis. Submesoscale instabilities, including mixed barotropical/baroclinic and symmetric instability then appear, driving vigorous submesoscale motions. Frontogenetic tendency analysis reveals that this frontogenesis is primarily driven by two ageostrophic processes, horizontal advection and vertical straining. Our findings elucidate a potential mechanism in idealized simulations whereby mesoscale eddy asymmetries catalyze submesoscale motions.

Beibei Zhou, Yingshuang Li, Feng Xu et al.

As a key vehicle for ecological conservation, National Parks (NPs) require accurate and timely land cover (LC) information for refined management. However, complex terrain and frequent human activities pose challenges to efficient LC extraction. This study focuses on the Chengdu section of the Giant Panda National Park and proposes a framework of multisource data integration, dynamic feature selection, algorithm performance evaluation, temporal sample migration, and LC change analysis. Sentinel-1, Sentinel-2 A, and SRTM data are integrated to construct 67 multidimensional features. Recursive feature elimination combined with Bayesian optimization is used for feature selection, and the classification performance of random forest (RF), support vector machine, and classification and regression tree are compared. Spectral angle mapper and spectral Euclidean distance are introduced for temporal sample migration. Results show that the RF classifier with optimized features yields the best performance, achieving an overall accuracy of 0.9330 and a Kappa coefficient of 0.9196, significantly outperforming GLC_FCS30D, Esri Land Cover, and China Land Cover Dataset. Accuracy after sample migration remains above 0.8800 annually. The framework effectively identified bamboo forests critical to panda habitats. For example, using only water indexes, bamboo forest producer accuracy was 0.0555, but increased to 0.8571 with added spectral and vegetation features. From 2018 to 2023, woodland increased by 64.77 km<inline-formula><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula> and bamboo forest by 22.26 km<inline-formula><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula>, while barren land and construction land increased by 116.04km and 174.28 km<inline-formula><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula>. The proposed framework effectively enhances LC monitoring in mountainous environments and provides technical support for conservation planning and ecological supervision in NPs.

Huiyu Ding, Jun Liu, Zhihui Wang et al.

The core of hyperspectral image (HSI) classification lies in the effective fusion of spatial-spectral features. However, traditional methods are limited by the capacity of handcrafted feature representation, while deep learning methods face challenges such as overfitting with small sample sizes and high computational complexity. This article proposes a Mamba-driven multiscale spatial-spectral fusion network (M²S²F-Net). This network extracts spatial-spectral features at different granularities through the spatial-spectral multigranularity feature extraction module, adaptively enhances the spatial-spectral correlation through the spatial-spectral fusion attention module, optimizes feature fusion by combining local and global streams with the feature fusion enhanced vision transformer, and establishes long-sequence dependencies using the dual-path feature fusion mamba. The M²S²F-Net employs a multistage feature fusion strategy of &#x201C;coarse fusion-fine optimization-strong screening&#x201D; to achieve efficient classification with few samples. The network was validated on three publicly available HSI datasets to demonstrate its superiority in few-shot scenarios, with significant improvements in classification accuracy. It also exhibited remarkable classification performance across different numbers of training samples.

Zih-Wei Tang, Liang-Chi Wang, Huei-Fen Chen et al.

Abstract To address the environmental changes in the South China coastal region and to investigate the interplay among sea-level fluctuations, monsoon variability, and sediment dynamics, a sediment core from the Pinqing Lagoon was extracted, covering the last 8.5 ka. Furthermore, multiple proxies were analyzed in the core, including grain size end-members (EM1, EM2, and EM3), magnetic susceptibility and S-ratio, the carbon (C) isotopic composition of organic matter, its carbon and nitrogen (N) contents, the resulting C/N ratio, and Itrax XRF-derived elemental ratios such as Mn/Ti, Si/Ti, K/Ti, and Fe/Ti. The results reveal that changes in sea level play a primary role in shaping the lagoon sedimentary and geochemical evolution, with EASM-driven runoff acting as a secondary control on terrestrial sediment supply, especially during low sea-level phases. During the 8.5–6.8 ka, low water levels, strong EASM-driven runoff, and dominant terrestrial C₄ plant input resulted in coarse detrital sedimentation (high EM2 and low S-ratio) and poor bottom water oxygenation (low Mn/Ti). Between 6.8 and 5.8 ka, despite already high sea levels, the lagoon underwent rapid deepening, with a shift toward in-situ aquatic productivity, improved oxygenation, and finer sedimentation (EM1 dominance and high S-ratio), likely reflecting local geomorphological changes. From 5.8 to 4.2 ka, as sea level stabilized, the lagoon became stratified and marine-influenced, with low oxygenation, minimal terrestrial input, and background fine-grained sedimentation. After 4.2 ka, stable high water levels and low runoff persisted. A prominent EM3 peak between 0.4 and 0.2 ka, coinciding with the Late Little Ice Age (LIA), reflects frequent typhoon-induced high-energy deposition, supported by coarse grain size, elevated MS, and increased Si/Ti, K/Ti, and Fe/Ti ratios. Overall, the results highlight that long-term sea-level fluctuations primarily controlled lagoonal sedimentation and oxygenation, while EASM variability shaped runoff-driven detrital input.

Paolo Ventura, Silvia Tosi, Flavia Dell’Agli et al.

Planetary nebulae, among the most fascinating objects in the sky, have been extensively investigated in the past years, because their study provides important information on the low and intermediate mass stellar populations of the host environment, formed earlier than ∼100 Myr ago. We report on the recent progresses achieved in the study of this class of objects, regarding the dust and gas content of the nebula, which allows us to reconstruct the dust formation process occurred during the previous asymptotic giant branch phase, and the chain of events occurred since the stars leave the asymptotic giant branch until the planetary nebula stage. The possibility offered by these studies to assess the role played by the stars of low and intermediate mass as dust manufactures in the Universe is also commented.

Gourab Giri, Gourab Giri, Christian Fendt et al.

This review explores the field of X-shaped radio galaxies (XRGs), a distinctive subset of winged radio sources that are identified by two pairs of jetted lobes which aligned by a significant angle, resulting in an inversion-symmetric structure. These lobes, encompassing active (primary) and passive (secondary) phases, exhibit a diverse range of properties across the multiple frequency bands, posing challenges in discerning their formation mechanism. The proposed mechanisms can broadly be categorized into those related either to a triaxial ambient medium, into which the jet propagates, or to a complex, central AGN mechanism, where the jet is generated. The observed characteristics of XRGs as discovered in the most substantial sample to date, challenge the idea that there is universal process at work that produces the individual sources of XRGs. Instead, the observational and numerical results rather imply the absence of an universal model and infer that distinct mechanisms may be at play for the specific sources. By scrutinizing salient and confounding properties, this review intends to propose the potential direction for future research to constrain and constrict individual models applicable to XRGs.

Xuanting Hao

Abstract Breaking‐wave induced bioluminescence is a critical component of the biogeochemical process in the ocean. Understanding bioluminescence is important for monitoring red tides caused by bioluminescent microorganisms. In this study, we present the first numerical effort to quantify bioluminescent light intensity based on high‐fidelity direct numerical simulations of breaking waves and a quantitative bioluminescent model. The dynamics of breaking waves are extensively validated through comparison with existing studies. We find that the time‐averaged and Lagrangian‐averaged shear stress saturates as surface tension effects decrease and wave steepness increases. The spatial distribution of light intensity correlates with the wave crest overturning and air bubbles generated in plunging breakers. Furthermore, we observe that the maximum light intensity asymptotically approaches the emission of single cells, suggesting the potential for cost‐effective prediction models in future studies.

Qian WU, Wenjie HE, Xiejun ZHANG et al.

Objective: To analyze and summarize the clinical and MRI manifestations of patients with idiopathic normal pressure hydrocephalus (iNPH) diagnosed via surgery in order to improve the understanding of this disease. Methods: We performed a retrospective analysis of the clinical and preoperative MR (including 3DT1WI, T2WI, and T2 FLAIR) data of 56 patients with iNPH diagnosed via shunt surgery at our hospital to evaluate and describe MR linear parameters and common radiological features. Results: Among the 56 patients with iNPH, 91.1%, 60.7%, and 42.9% showed gait disturbance, cognitive impairment, and urinary disturbance, respectively; the classical triad accounted for 23.2%. The most common comorbidities were hypertension (51.8%), diabetes (28.6%), and PD (12.5%). In the analysis of the 56 patients’ MR images, 82.1% had acute callosal angle and 39.3%, positive disproportionately enlarged subarachnoid space (DESH) signs , with a mean DESH score of (5.24±1.27). Conclusion: Patients with confirmed iNPH most often also have hypertension, diabetes mellitus, and PD. The classical triad is less frequent, and the positive rate of typical MR signs is not high. Thus, the accurate diagnosis and prognosis prediction of negative patients remains challenging and should be combined with other clinical examinations to clarify the diagnosis and treatment.

Yoann Arhant, Olga Lopera Tellez, Xavier Neyt et al.

Seabed characterization consists in the study of the physical and biological properties of the of ocean floors. Sonar is commonly employed to capture the acoustic backscatter reflected from the seabed. It has been extensively used for automatic target recognition (ATR) within mine countermeasures (MCM) operations in shallow waters. However, conventional machine learning (ML) and deep learning approaches face challenges in automatically mapping the seabed due to noise and limited labels. Thus, this article introduces the Deep Supervised Semantic Segmentation model for Seabed Characterization (D4SC), tailored for addressing challenges associated with sonar data. D4SC employs convolutional neural networks, specific high-resolution (HR) synthetic aperture sonar (SAS) data preprocessing and data augmentation methods, including the novel boundary pixel label rejection, and moves from the low-label regime. Performance comparisons against standard methods in the literature are conducted, demonstrating D4SC&#x0027;s superiority on challenging HR SAS survey datasets from real-world MCM exercises at sea. In addition, this work thoroughly explores the effect of the quality of the datasets, the robustness of training models on Out-of-Distribution data, and the estimation of epistemic uncertainty to refine predictions at large scale.

Anna Rogowitz, Marcel Thielmann, Katrin Kraus et al.

Abstract We performed deformation experiments on omphacite‐garnet aggregates at a temperature of 1000°C, a confining pressure of 2.5 GPa, and a strain rate of 3 × 10−6 s−1 and complemented them by numerical simulations to gain insight into the role of garnet fraction for the deformation behavior of dry eclogite, with a focus on strain weakening mechanisms. We determined the spatial and temporal evolution of strain and strain rate by basing numerical simulations on experimentally derived microstructures, and thereby identified characteristic deformation mechanisms. Pure omphacite and garnet aggregates deform by two different mechanisms. Internally strained clasts and low‐angle grain boundaries indicate crystal plasticity for omphacitite; the fracture dominated fabric of garnetite documents brittle deformation. Electron channeling contrast imaging, however, revealed low‐angle grain boundaries and free dislocations in garnet crystals, suggesting that minor crystal plasticity accompanies the brittle failure. Eclogitic aggregates show varying deformation behavior between the two end‐members shifting from crystal plastic toward brittle deformation with increasing garnet content. All samples exhibit strain weakening. The intensity of weakening shows a positive correlation with the garnet content. Our combined experimental, numerical, and microstructural investigations suggest that the majority of strain weakening is associated with crystal plastic processes in omphacite. Numerical simulations and experiments show that a garnet content above 25% enhances the activity of crystal plastic processes in omphacite and results in strain localization, which subsequently weakens the eclogite.

Yufan Wu, Zhen Huang, Qixiong Gu et al.

Abstract Water and mud inrush caused by fault is a geological disaster characterized by high frequency and huge destructiveness. It is important to study the evolutionary laws of water inrush in fault fracture zones with various filling types. The effect of filling gradation on the mesoscopic structure and seepage characteristics of fault fracture zones was investigated. The law of water inrush evolution and water inrush characteristics of fault-fractured zones with different filling gradations and strong zoning filling characteristics were studied. The results showed that for the larger Talbot gradation indices, the mass of water inrush and the fractal dimension of the lost particles were larger, the peak water pressure and the mass of the lost particles were smaller, and the duration of the initial impermeability stage was shorter for the same loading water pressure. For the fault fracture zones with strong zoning filling characteristics, the peak water pressure, the mass of water surges, and the mass of lost particles were larger, the fractal dimension of the lost particles was smaller, and the duration of the initial impermeability stage was shorter for the fracture zones with larger filling gradation were used as the initial impermeability zones. Furthermore, with larger filling gradation, we observed a greater proportion of large pores, a larger equivalent throat radius, higher pore connectivity, and coordination numbers. Filling gradation and confining pressure greatly affected the permeability of the fault. The permeability decreased by 98.71% when the Talbot gradation indices decreased from 1.25 to 0.6, and decreased by 58.4% when the confining pressure increased from 5 MPa to 15 MPa.

E. Mottola

Gravity and general relativity are considered as an Effective Field Theory (EFT) at low energies and macroscopic distances. The effective action of the conformal anomaly of light or massless quantum fields has significant effects on macroscopic scales, due to associated light cone singularities that are not captured by an expansion in local curvature invariants. A compact local form for the Wess-Zumino effective action of the conformal anomaly and stress tensor is given, requiring the introduction of a new light scalar field, which it is argued should be included in the low energy effective action for gravity. This scalar conformalon couples to the conformal part of the spacetime metric and allows the effective value of the vacuum energy, described as a condensate of an exact 4-form abelian gauge field strength F = dA, to change in space and time. This is achieved by the identification of the torsion dependent part of the Chern-Simons 3-form of the Euler class with the gauge potential A, which enters the effective action of the conformal anomaly as a J · A interaction analogous to electromagnetism. The conserved 3-current J describes the worldtube of 2-surfaces that separate regions of differing vacuum energy. The resulting EFT thus replaces the fixed constant Λ of classical gravity, and its apparently unnaturally large sensitivity to UV physics, with a dynamical condensate whose ground state value in empty flat space is Λeff = 0 identically. By allowing Λeff to vary rapidly near the 2-surface of a black hole horizon, the proposed EFT of dynamical vacuum energy provides an effective Lagrangian framework for gravitational condensate stars, as the final state of complete gravitational collapse consistent with quantum theory. The possible consequences of dynamical vacuum dark energy for cosmology, the cosmic coincidence problem, and the role of conformal invariance for other fine tuning issues in the Standard Model are discussed.

Vikanisa Rahmadany, Martinus Edwin Tjahjadi, Fransisca Dwi Agustina

The morphologies of the Pandansari Village (Ngantang District, Malang Regency, Indonesia) are vulnerable to landslide disasters that may damage human properties, infrastructures, and even fatalities. Landslide disaster mitigation can be carried out by conducting disaster-prone mapping utilizing Unmanned Aerial Vehicle (UAV) photogrammetry along with geographic information systems (GIS) to produce precise Digital Elevation Model/Digital Terrain Model (DEM/DTM). The purpose of this study is to analyze areas prone to landslides using precision DTM data from UAV technology integrated with geospatial data. DEM is widely used for disaster mapping applications in the form of DTM, representing the ground surface. DTM can be generated from UAV images with photogrammetric processing and additional procedures for removing non-ground objects. This study utilizes PCI Geomatics software to remove vegetation and human-made objects off the ground surfaces semi-automatically. The evaluation revealed that LE 90% of the DTM has only deviated at approximately 0.81 m. This value follows the introductory map geometric accuracy provisions according to BIG No.15 of 2014 for a scale of 1:2500 in class 2. The landslide hazard map classifications using the landslide estimation Puslittanak are dominated by a high classification landslide hazard level with an area of 20.1 ha (48%). In addition, the validation of the landslide-prone map using the accuracy assessment method obtained a percentage of 83%.

G. A. S. Picanço, C. M. Denardini, P. A. B. Nogueira et al.

<p>This work uses the Disturbance Ionosphere indeX (DIX) to evaluate the ionospheric responses to equatorial plasma bubble (EPB) events from 2013 to 2020 over the Brazilian equatorial and low latitudes. We have compared the DIX variations during EPBs to ionosonde and All-Sky Imager data, aiming to evaluate the physical characteristics of these events. Our results show that the DIX was able to detect EPB-related TEC disturbances in terms of their intensity and occurrence times. Thus, the EPB-related DIX responses agreed with the ionosphere behavior before, during, and after the studied cases. Finally, we found that the magnitude of those disturbances followed most of the trends of solar activity, meaning that the EPB-related total electron content variations tend to be higher (lower) in high (low) solar activity.</p>

Sebastian M. Richiano, Fernando J. Gómez, Renata G. Netto

 Estimados lectores de LAJSBA, como saben, nuestra revista ha renovado su equipo editorial para el período 2018-2022. Como Editor (Sebastian Richiano) y Editores Asociados (Renata Netto y Fernando Gómez), queremos contactarnos con ustedes por primera vez, en este caso iniciando el Volumen 25. Nos gustaría agradecer a la Comisión Directiva de la Asociación Argentina de Sedimentología por confiar en nosotros para esta tarea tan importante y comprometida. La revista, desde su inicio en 2005 (en continuación de la AASRevista que se publicara desde 1994), ha ido mejorando progresivamente su calidad y su visibilidad dentro de la comunidad científica. Esto se debe principalmente al esfuerzo de los diferentes equipos editoriales y, en este sentido, nos gustaría agradecer al ex editor Ernesto Schwarz y a la ex editora asociada Diana Cuadrado por su importante labor durante los últimos 4 años.

Peng Zhang

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kiloton liquid scintillator detector with neutrino mass hierarchy determination as primary physics goal. The other measurements, including precise neutrino oscillation parameters, solar neutrino, geo-neutrino, supernova neutrinos and the diffuse supernova neutrinos background, will be performed at the same time. The detector will be built in a 700 meter deep underground laboratory. A multi-eto detector, composed of a Top Tracker and a Water Cherenkov, will be installed for cosmic muon detection and background reduction. The Top Tracker detector is placed above the central detector, and is composed of three layers of scintillating strips. The outer part of the Central Detector is filled with water and equipped with about 2400 MCP-PMTs (20 inches) to form the Water Cherenkov detector used for muon tagging. Thanks to the Veto detector, the cosmic muon induced fast neutron background can be reduced to a level of about 0.06/day.

K. Sato, Y. Itow, H. Menjo et al.

Atmospheric neutrino flux calculation ATMNC has greatly contributed to the physics of neutrino experiments including Super-Kamiokande. Since next-generation large-scale experiments, such as Hyper-Kamiokande, are expected a large improvement of statistical errors, it is desirable to reduce systematic errors associated with uncertainty of the flux calculation. The dominant uncertainty of the ATMNC calculation arises from insufficient understanding of the hadron interactions inside air showers caused by cosmic rays. In order to improve the accuracy of the hadron interaction model, many precision measurements for hadron production using accelerator beams have been performed or planned. In this report, we discuss a strategy to update ATMNC calculation to reduce its uncertainty by incorporating such measurements.

M. Daniel

VERITAS has been observing the northern sky at TeV energies with full sensitivity since 2007. Consisting of a ground based array of four 12 m imaging atmospheric Cherenkov telescopes, sited in southern Arizona, it is one of the world’s most sensitive detectors of gamma-rays between 85 GeV to 30 TeV. VERITAS maintains a broad scientific programme in many areas of astroparticle physics, including, but not limited to: studies of the acceleration, propagation and indirect measurements of cosmic rays and their spectra; searching for indirect detection signatures of dark matter candidates; and tests of fundamental physics, such as setting constraints on Lorentz invariance violation. There is also an active multi-messenger programme with partners in the electromagnetic, neutrino, and gravitational wave sectors. We review here the current status and some recent results from VERITAS and examine the prospects for future studies.

W. Wan

O n May 20, 2020, Professor Weixing Wan of the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS), a world renowned space scientist and planetary physicist, passed away at age of 62. Prof. Wan was an academician of the Chinese Academy of Sciences (CAS). He served as a member of the 13th National People's Congress Standing Committee, and of the 14th Central Committee of Jiusan Society. He also served as the chief scientist of China's first Mars exploration mission, Tianwen-1, and the director of the Key Laboratory of Earth and Planetary Physics of the CAS. His passing is a great loss to the science community. This article was especially written in memory of him.

Alessandro Sandrin

Play analysis has been widely used in hydrocarbon exploration for decades with great success. In recent years, progress has also been made to describe reservoir properties of very low permeability reservoirs. However, comparatively little research has been conducted into play analysis for such reservoirs, which may lead to misleading estimates of their hydrocarbon potential. Here, the concept of a semi-conventional play is defined and characterised as having a reservoir of such low permeability that a hydrocarbon column can form down-dip of an effective dry trap. A new exploration approach is proposed for such plays using the Chalk Group Play in the Danish North Sea as an example. It is suggested that together with the usual risk elements, a more detailed analysis of ‘charge’ is necessary, paying particular attention to identifying possible hydrocarbon entry-points, palaeostructures and the maximum distance from these entry-points that the hydrocarbons may have reached since they first entered the reservoir. The application of this novel approach for semi-conventional plays in mature basins could help unlock further resources in proximity of existing fields, and reduce the risk of failure in frontier exploration.