Search Results (1,174)

Quantifying groundwater storage in karst aquifers remains challenging because of their heterogeneous structure and the scarcity of direct observations. This study proposes a pragmatic approach for characterizing storage and water availability in karst systems at the regional scale using long-term hydrographs from 16 Swiss karst springs and rivers. We distinguish between seasonal storage, associated with recharge events, and low-water storage, which sustains discharge during periods without significant recharge. Seasonal storage was estimated at approximately 30–70 mm for most investigated systems, while total storage reached up to about 140 to 180 mm at some sites, based on recharge–discharge modelling. Low-water storage was estimated to be on the order of 200 mm across most investigated systems, despite differences in hydrogeological settings. Analysis of low-water recession curves showed that most natural springs analyzed in this study followed a similar master recession curve, with low-water conditions defined as beginning at a specific transition discharge of 11.25 L s⁻¹ km⁻². This similarity provides the basis for a regional drought index that estimates the volume of remaining groundwater storage and forecasts discharge several weeks in advance. The results also support a conceptual model in which epikarstic, epiphreatic, and deeper storage compartments attenuate short-term discharge variability while sustaining low-water discharge over prolonged periods. Comparison with non-karst catchments shows that karst hydrogeological systems dampen peak flows but sustain baseflow through distinct storage reservoirs. This approach delivers quantitative indicators to assess drought, manage groundwater, and foresee water shortages in karst regions. Future work will test its validity outside the Swiss dataset. Despite discussed uncertainties in discharge measurements and catchment delineation, results demonstrate that dedicated hydrograph-based analyses can yield robust and transferable insights into karst groundwater storage at regional scales. Full article

Seepage pressure time series of concrete dams are governed by reservoir water level, rainfall, temperature and long-term aging effects, featured by strong nonstationarity and complex multi-scale fluctuations. Existing decomposition–ensemble methods ignore nonlinear coupling among scale components, suffering low prediction accuracy and poor physical interpretability. Current model fusion schemes fail to adapt to differentiated evolution mechanisms of frequency-varying seepage components and cannot fully mine implicit cross-scale nonlinear correlations. To overcome these drawbacks, this study proposes a concrete dam seepage pressure prediction approach integrating ensemble empirical mode decomposition, multi-scale preprocessing, and optimized dual-model selection combining ridge regression and Transformer–BiLSTM. Ensemble empirical mode decomposition adaptively denoises and decouples raw seepage series into high-, medium- and low-frequency IMFs according to oscillation cycles. A normalized Comprehensive Optimization Index is constructed to parallelly train ridge regression and Transformer–BiLSTM for each component and select the optimal submodel dynamically. A fully connected nonlinear fusion layer reconstructs multi-scale predictions to retain inherent component coupling features, replacing traditional simple linear superposition. Engineering cases verify that the proposed model efficiently captures periodic laws of key influencing factors, significantly boosting prediction accuracy and generalization capacity, thus possessing prominent theoretical and practical engineering application values. Full article

Background: Hantavirus pulmonary syndrome (HPS), also designated hantavirus cardiopulmonary syndrome, is caused by New World hantaviruses, principally Sin Nombre virus in North America and Andes virus in South America. The syndrome is characterized by rapidly progressive noncardiogenic pulmonary edema and myocardial depression, with case fatality rates of 25% to 40%. A 2026 outbreak aboard an expedition cruise ship in the South Atlantic, comprising 13 cases and three deaths, confirmed that Andes virus can be transmitted between humans in a confined setting remote from the rodent reservoir. Methods: Virological, pathophysiological, clinical, and therapeutic aspects of HPS were reviewed, with particular emphasis on cardiopulmonary mechanisms. Sources were identified through PubMed, Scopus, and Google Scholar, with priority given to original research articles, clinical series, and controlled trials published through 2025. Literature published in English and Spanish was included. Results: Pathogenic hantaviruses enter endothelial cells and platelets via αvβ3 integrins, disrupting the VEGF-VEGFR2 signaling axis and rendering endothelial cells hypersensitive to physiological VEGF concentrations. Expansion of CD8+ T cells and activated macrophages releases TNF-alpha, IFN-gamma, and nitric oxide, amplifying microvascular permeability and contributing to myocardial depression. Autopsy studies demonstrate direct hantaviral myocarditis with viral antigen in cardiac endothelium and interstitial macrophages. Transpulmonary thermodilution confirms simultaneous hypovolemia, reduced global ejection fraction, and elevated extravascular lung water. Because the incubation period is long and the cardiopulmonary phase is substantially immune-mediated, seroconversion precedes rather than follows clinical deterioration, which preserves the diagnostic utility of IgM serology in a disease that can kill within 48 h. VA-ECMO initiated at the first signs of cardiopulmonary decompensation has reported survival rates approaching 80% in selected experienced centers. No antiviral has demonstrated efficacy in controlled trials during the cardiopulmonary phase, and no licensed vaccine exists. Conclusions: HPS produces a mixed shock state through increased microvascular permeability, T cell-mediated immunopathology, and direct myocarditis. Management follows a stepwise algorithm: suspected HPS triggers immediate complete blood count with peripheral blood smear and concurrent hantavirus IgM serology and RT-PCR, followed by ICU admission, conservative fluid resuscitation guided by transpulmonary thermodilution, and early contact with an ECMO-capable center at the first sign of rising lactate, falling cardiac index, refractory shock, arrhythmia, or rapid oxygenation failure. Full article

Full-field water saturation is central to waterflood surveillance but cannot be observed continuously across a reservoir, whereas well histories provide sparse dynamic evidence. We formulate target-time saturation reconstruction as a mapping from static geology, well locations, scheduled controls, simulated multi-well production responses, and development time to a two-dimensional saturation field. The water-balance-guided saturation network (WB-SatNet) combines a U-Net spatial pathway, a fixed-order gated recurrent unit (GRU) history encoder, explicit time conditioning, and a closed-boundary water-storage consistency term. Experiments used 400 geological realizations, 800 simulation runs, six target times, realization-wise train/validation/test splitting, and three random seeds. On the held-out test set, WB-SatNet achieved a mean absolute error (MAE) of 0.01175, a coefficient of determination (${\mathrm{R}}^2$) of 0.98145, a structural similarity index measure (SSIM) of 0.99177, a flooded-area intersection over union (IoU) of 0.95523, and a global storage-consistency error of 0.00944. Its mean MAE was 6.31% lower than that of TCN-U-Net, the strongest temporal convolutional network baseline. Target-time, component-ablation, flooded-area, storage-consistency, history-window, noise, and operating-regime analyses support a monitoring-oriented interpretation. These results indicate that WB-SatNet provides an effective framework for production-history-conditioned water-saturation reconstruction and waterflood state monitoring in the investigated setting. Full article

Carbon dioxide water-alternating-gas (CO₂-WAG) flooding simultaneously enables carbon emission mitigation, improved oil displacement efficiency, and expanded gas sweep coverage. Nevertheless, the field performance of this technology remains significantly constrained by gravity override effects, especially in ultra-thick oil reservoirs. In this work, a synthetic heterogeneous dipping mechanistic reservoir model is constructed. Using a quantitative metric for gravity override index in WAG processes, the variation patterns of gravity override under various operational factors are systematically analyzed. Furthermore, the eXtreme Gradient Boosting (XGBoost) machine learning algorithm is employed to conduct feature importance analysis of the controlling factors, identifying parameters with the most substantial impacts. The results indicate that well spacing, oil production rate, WAG injection strategy, and WAG slug duration all exert pronounced effects on both gravity override index and oil recovery factor. Gravity override is confirmed as the dominant factor governing the production performance of WAG flooding in ultra-thick reservoirs. In addition, an optimal combination of operational parameters exists that counterbalances the adverse effects of gravitational and viscous forces, thereby maximizing gas sweep efficiency, delaying gas breakthrough, and enhancing oil recovery. This study provides valuable insights and technical guidance for gas channeling mitigation, vertical gas sweep improvement, and efficient development of analogous ultra-thick reservoirs. Full article

Deep shale reservoirs in the tectonically complex margin of the southern Sichuan Basin have experienced multistage deformation, resulting in strong spatial heterogeneity of the present-day geostress field. However, the influence of stress heterogeneity on multiscale pore structure evolution and reservoir quality remains poorly constrained. Here, we integrate in-situ stress measurements, overburden porosity and permeability experiments, CO₂/N₂ adsorption, high-pressure mercury intrusion, SEM-MAPS (Scanning Electron Microscopy-MAPS) pore imaging, stress well profile interpretation, and multifractal analysis to quantify the controls of present-day geostress heterogeneity on pore structure evolution in deep Longmaxi Formation shale. The results show that the present-day stress regime is characterized by a strike-slip pattern (σ_H > σ_v > σ_h), with significant variations among different structural deformation zones. Increasing structural deformation results in enhanced differential stress, increasing by 30–80% from gentle structures to tight folds and fault-affected zones, accompanied by a 60–70° rotation of the maximum principal stress orientation. Differential stress, effective stress, differential stress coefficient, and stress structure index exhibit strong negative correlations with porosity, whereas permeability decreases nonlinearly with increasing stress, indicating progressive pore-throat compression and connectivity degradation under heterogeneous stress conditions. Multifractal analysis reveals that pore-size domains exhibit different sensitivities to stress heterogeneity. The macropore fractal dimension (DN3) shows the strongest response, followed by mesopores (DN2), whereas micropores (DN1) exhibit relatively limited variations. Fault-affected zones and strongly deformed regions display higher DN3 values (>2.8), reflecting enhanced complexity of macropore and fracture networks. In contrast, gentle structural zones characterized by curvature values <0.10 km⁻¹ and distances >500 m from faults exhibit relatively low and stable fractal dimensions (<2.73), indicating more homogeneous pore structures. Increasing stress heterogeneity induces the transformation of organic matter pores from regular subcircular shapes to flattened and slit-like morphologies, accompanied by pore-size migration toward smaller scales (<15 nm) and enhanced pore heterogeneity (Df > 1.35). These findings reveal that present-day geostress heterogeneity governs shale pore fractal evolution and promotes the transition from micropore-dominated to heterogeneous macropore–fracture systems. This study provides quantitative insights into stress-controlled pore evolution and reservoir quality evaluation in deep shale reservoirs under complex tectonic settings. Full article

High-fidelity reservoir simulation is too costly for multi-query tasks such as history matching and production optimisation. Existing reduced-order models (ROMs) mitigate this cost but generally lack uncertainty quantification, spatial sparsity, and interpretable mode-to-geology mappings. We introduce USX-PGD (Uncertainty-aware, Sparse, and eXplainable Proper Generalised Decomposition), a non-intrusive ROM for two-phase immiscible flow that addresses all three gaps within a single greedy Alternating Least Squares framework. USX-PGD is benchmarked against Proper Orthogonal Decomposition (POD), standard Proper Generalised Decomposition (PGD), and an intermediate Uncertainty-aware Sparse PGD (US-PGD) variant, on a formation-aware upscaled coarse-grid ($30\times 110\times 34$ cells) representation of the SPE10 Model 2 benchmark, a heterogeneous two-phase reservoir with permeability contrasts spanning six orders of magnitude. US-PGD adds sparsity-promoting thresholding and bootstrap resampling to certify a confidence interval on reconstruction accuracy; USX-PGD further adds formation energy decomposition, mode dominance mapping, breakthrough attribution, and mode sensitivity indexing, attributing the reduced-order modes to identifiable geological formations. All four methods reproduce the reference production curves to within $11.03$–$11.05\%$ NRMS at online reconstruction times of 51–63 ms; the sparse and explainable variants achieve comparable accuracy while additionally providing $41.8\%$ spatial sparsity and a certified $95\%$ confidence interval. All four ROMs compress and replay an already-simulated trajectory, not predict new, unsimulated scenarios; USX-PGD is offered as a reproducible, physically transparent foundation for such multi-query workflows, with predictive extension identified as future work. Full article

Deep coalbed methane (CBM) represents a strategic successor field for unconventional oil and gas exploration and development in China, and fluid mobility is a key parameter determining CBM recovery rates. Existing NMR-based studies on coal rock pore structure and fluid mobility suffer from three deficiencies: a lack of coal rock classification based on T₂ spectral morphology, failure to incorporate fractal characteristics into pore classification, and insufficient understanding of fluid mobilization mechanisms in different pore types during gas-driven recovery. This study investigates deep coal rocks of the Taiyuan Formation in the Linxing Block, eastern Ordos Basin, using low-field nuclear magnetic resonance (LF-NMR), saturation gas displacement experiments, and fractal theory. Deep coal rocks were classified into three types based on T₂ spectral peak morphology under saturated conditions: Type I (central main peak), Type II (left-shifted main peak), and Type III (balanced bimodal peak). A fractal-based method was established to subdivide fluid-filled pores into four types: P1-1, P1-2, P1-3, and P2. Through multiple nitrogen displacement experiments, the fluid mobilization characteristics of each pore type at different displacement stages were quantitatively characterized. A fluid mobility index was proposed to comprehensively evaluate the overall fluid mobility of coal rocks. The results indicate that Type I coal rocks exhibit the highest fluid mobility (54.83% after three displacement cycles), with P1-3 pores as the primary mobile fluid reservoir, whereas Type II and Type III coal rocks show lower mobility (27.70% and 32.89%, respectively), with P1-2 pores as the dominant contributors. Pore structure complexity exhibits a significant nonlinear evolutionary relationship with fluid mobility. The fluid mobility index demonstrates a strong positive correlation with the degree of mobile fluid, validating its effectiveness in characterizing fluid mobility in deep coal rock reservoirs. These findings provide a theoretical foundation for sweet spot identification and development optimization in deep coal gas reservoirs. Full article

Strong heterogeneity in unconventional reservoirs leads to complex fracture propagation and challenges in quantitative stimulation evaluation. This study integrates true triaxial fracturing experiments, three-dimensional CT reconstruction, multi-field coupled numerical simulation, and multiple linear regression to investigate the fracture behavior of Gulong shale (Q1, Q9) and tight sandstone under supercritical carbon dioxide (SC-CO₂) fracturing. A fracture complexity index (FCI) that incorporates fractal dimension, spatial uniformity, and aperture distribution is proposed as a quantitative metric. The results show that SC-CO₂ significantly reduces breakdown pressure and increases fracture complexity compared to water. For Q9 shale, SC-CO₂ gives a breakdown pressure of 32.91 MPa (10.46% lower than water), a fractal dimension of 2.41, and an FCI of 8.92. In tight sandstone, the SC-CO₂ breakdown pressure is 34.12 MPa, whereas water increases it to 44.50 MPa; the fractal dimension and FCI are only 2.05 and 3.40, respectively, lower than those of shale fractured with water. Multiple linear regression quantifies contribution weights: lithological weak-plane development dominates fracture complexity (41.6%), far exceeding the brittleness index. The injection rate mainly controls stimulation scale: the damage area ratio rises from 1.79% to 2.90% when the rate increases from 10 to 40 mL/min. The horizontal stress difference is key to complexity enhancement: the fractal dimension increases from 1.9230 to 1.9901 as the stress difference rises from 0 to 4 MPa. The numerical simulations further reveal the coupled thermal-hydraulic-mechanical effects. The proposed FCI-based evaluation and regression models provide a quantitative framework for optimizing SC-CO₂ fracturing design in heterogeneous unconventional reservoirs. Full article

Dam removal is a direct measure to restore river connectivity, but the assessment of its ecological effects has long been constrained by the lack of continuous monitoring data across multiple trophic levels. Based on eight years (2017–2024) of continuous field monitoring data from the Heishui River, a first-order tributary of the Jinsha River, this study systematically analyzed the spatiotemporal dynamics of phytoplankton, zooplankton, and fish communities before and after the removal of the Laomuhe Dam. Ecopath models were constructed annually for six ecological units to quantitatively assess the restructuring effect of dam removal on the structure and function of the aquatic food web. The results showed that: (1) Plankton communities were highly sensitive to the disturbance of dam removal. In the early stage after dam removal (2019), the diversity of phytoplankton and zooplankton across the whole river suffered a cliff-like decline; the Shannon index of zooplankton in the former reservoir area plummeted from 3.06 to 0.81. During the recovery period, diatoms and rotifers acted as pioneer groups for phytoplankton and zooplankton, respectively, and were the first to recover. By 2024, the proportion of copepods rose to the highest level during the study period, and the dominant group of the community shifted from rotifers to copepods. (2) Fish communities responded rapidly and positively to the restoration of connectivity. In the upstream reach adjacent to the dam site, the number of species increased from 3 before dam removal to 12 afterward; in the downstream reach, it increased from 2 to 15, with diversity index increases of 172% and 246%, respectively. (3) Ecopath model analysis revealed a recovery pattern of “structure first, function delayed” in the food web—species number and community composition could be re-established shortly after connectivity restoration, but the recovery of functional indicators such as the system omnivory index (SOI) and energy transfer efficiency (total primary production/total respiration, TPP/TR) lagged significantly behind. By the end of the study period, the upstream dewatered reach had not yet reached the level of the natural reference reach, and the downstream recovery rate and degree were better than those upstream. This study provides comprehensive time-series evidence for the long-term response of aquatic ecosystems to low-head dam removal and offers valuable references for guiding adaptive management of mountain rivers after dam removal. Full article

Industrial data products create economic value through embodied technical resources, current decision use, and future deployment rights. This article develops a Cost–Premium Valuation System (CPVS) that measures these channels as a quality-adjusted cost anchor, a data-attributable utility premium, and an activation-adjusted real-option premium. A recoverability coefficient connects the cost term to current technical, legal, and commercial usability, and an integration weight combines recoverable cost evidence with the business-based value indication. The application concerns a geological simulation and prediction model for oil and gas reservoirs. Enterprise records and two structured five-expert procedures produce a quality coefficient of 0.854 and a data-factor contribution rate of 47.6%. The cost anchor is CNY 166.957 million, the utility premium is CNY 143.544 million, and the option premium is CNY 87.078 million, giving an integrated value of CNY 205.156 million at an integration weight of 0.60. A fourteen-parameter analysis and 10,000 triangular draws yield a 5th–95th percentile range of CNY 181.368–214.347 million. Black–Scholes, a five-step CRR lattice, and a three-tranche rollout tree produce activation-adjusted option values within 1.04% of one another. The Reliability-Weighted Parameter Exposure index equals 0.4227 and ranks the inputs by combined value influence and evidence priority. CPVS thereby connects technical condition, cash flow, deployment readiness, and evidence quality with data maintenance, investment review, reuse preparation, and transaction design. Full article

The evaluation of fault sealing is important research content in the early evaluation of underground gas storage construction. To accurately predict the pressure limit of the fault, a new method involving the analysis of fault lateral sealing and a comprehensive evaluation of mechanical stability is proposed in this paper. The results show that the Shale Gouge Ratio values of the faults in the reservoir building area are all greater than the critical value, which can ensure the lateral sealing of this area. After reservoir development, pressure failure causes the horizontal principal stress to decrease, but the effective normal stress and shear stress on the cross section increase, the fault stability index increases to 0.8, and the risk of fault reactivation risk increases. The simulation results show that when the pressure decreases to 35.5 MPa or increases to 65.5 MPa, the Fault F1 stability index first approaches the critical value of 1, and the fault appears to fall into slip instability. This study shows that the safe operating pressure range of this reconstructed gas storage reservoir is 35.5~65.5 MPa. The quantitative evaluation results are given in this paper, and it also gives early warning of potential risks. Full article

High-altitude Andean páramo ecosystems are critical socio-ecological assets that provide key regulating and supporting services, yet they remain highly vulnerable to climate change and anthropogenic pressures. Understanding these services requires frameworks that integrate biophysical capacity with social valuation and demographic accessibility. In this study, we mapped and assessed belowground and aboveground carbon storage and species habitat provision across the altitudinal gradient (3160–4400 m.a.s.l.) of Cajas National Park (PNC), Ecuador, using a spatially explicit socio-ecological approach. Carbon stocks were modeled following The Intergovernmental Panel on Climate Change (IPCC) 2019 Refined Guidelines, combining reference soil organic carbon (SOC) stocks with aboveground biomass coefficients. Habitat provision was modeled through a multi-factor suitability index integrating Normalized Difference Vegetation Index (NDVI), elevation, water bodies, and interpolated climate surfaces. Biophysical supplies were weighted via a Delphi-based expert consultation and integrated with demographic census data (173,672 inhabitants in four adjacent parishes) to estimate actual service capture and effective benefits. Total carbon stocks in PNC were estimated at 1.49 million Mg C, with volcanic Andisols acting as the primary reservoir (97.5% of the total stock). Habitat suitability was highly heterogeneous, with critical refuge patches clustered around the park’s lacustric network and stable microclimatic zones. Socio-ecological mapping revealed that the eastern boundary of the park represents the highest hotspot of effective benefit capture, directly supplying vital water regulation and cultural services to the peri-urban populations of Sayausí and Baños. These results demonstrate the utility of integrating standard IPCC guidelines with the ECOSER protocol, offering a repeatable and transparent framework to guide spatial conservation planning and sustainable land-use zoning in vulnerable high-altitude protected areas. Full article

Background: Atrial stiffness can be estimated non-invasively using speckle-tracking echocardiography (STE) and has recently emerged as an outcome predictor. We aimed to assess left atrial (LA) and right atrial (RA) phasic function; the LA stiffness index (LASI), the RA stiffness index (RASI) and their sum; and the biatrial stiffness index (BASI) in dilated cardiomyopathy (DCM), and to test whether combining the two atria adds prognostic information over either index alone. Methods: A total of 121 patients with non-ischaemic DCM in sinus rhythm were followed prospectively for a composite endpoint of all-cause death, non-fatal cardiac arrest, or hospitalisation for heart failure decompensation. LASI was defined as the mitral E/e′ ratio divided by LA reservoir strain, RASI as the tricuspid Et/e′t ratio divided by RA reservoir strain, and BASI as the sum of the two. Cox models were adjusted for NYHA class, LV ejection fraction (LVEF), maximal LA volume (LAVmax) and pulmonary artery systolic pressure (PASP). Results: After 19 ± 11 months, 55 patients reached the endpoint. LA reservoir and contraction strain, all three components of RA strain and all three stiffness indices were significantly impaired in patients with events. All stiffness indices were independent outcome predictors in multivariable Cox regression (HR 2.79 [95% CI, 1.35–5.75], p = 0.006 for LASI, HR 1.84 [95% CI, 1.02–3.29], p = 0.04 for RASI and HR 2.74 [95% CI, 1.36–5.51], p = 0.005 for BASI). BASI showed the greatest increase in risk prediction (Δ likelihood ratio χ² test = 10.3, p = 0.001) over NYHA class, left ventricular ejection fraction, LA maximal volume and pulmonary artery systolic pressure. BASI showed the highest discrimination (AUC = 0.73); however, it was not significantly better than LASI or RASI alone. Conclusions: Left and right atrial stiffness are both associated with adverse outcome in DCM and add prognostic information to an LV-centred risk model. Their unweighted sum performs at least as well as either component and offers a single parsimonious measure, whose incremental clinical value remains to be established in larger, externally validated cohorts. Full article

This study assessed environmental changes observed during an integrated programme of microbiological bioremediation and macrophyte management in the Pasternik Reservoir in Starachowice, Poland. The monitoring programme included water and sediment analyses, repeated measurements of soft organic fraction thickness, observations of macrophyte management, Sentinel-2 Maximum Chlorophyll Index mapping, and historical catchment modelling. During the monitoring period, the mean thickness of soft organic fractions decreased by 78%, sediment dry matter increased, and several water quality variables showed favourable temporal changes. Rapid macrophyte regrowth required repeated cutting and increased the practical demands of vegetation management. Sentinel-2 imagery revealed marked spatial and seasonal variation in the red edge optical signal within the reservoir. The Maximum Chlorophyll Index was interpreted as a relative optical indicator rather than as a quantitative chlorophyll a product. Nutrient Delivery Ratio modelling was used only to provide historical catchment context for 1990–2018. Because the study involved one reservoir and did not include an untreated reference site, the observed changes cannot be attributed exclusively to the management programme. The study shows the value of combining field measurements, satellite observations, and catchment information in the adaptive monitoring of small eutrophic reservoirs. Full article