Flow Pathways Research Articles

The long lives of subducted spice and vorticity anomalies in the subtropical oceans

Abstract Subtropical cells, which exist in nearly all ocean basins, connect subducting subtropical waters to upwelling sites along the equator. This tight link between the subtropics and the tropics, on a scale of 5-15 years, is well-established in a time-averaged sense by modeling and observations. Recently, evidence has emerged of spice and potential vorticity anomaly persistence along mean flow pathways on isopycnals. We provide the first global view of subtropical water mass anomaly propagation, using both an observational dataset and the Estimating the Circulation and Climate of the Ocean (ECCO) state estimate Version 4 Release 4. In this global synthesis that complements the existing body of largely regional studies, we find long-lived interannual water mass anomalies that translate along mean advective pathways in all ventilated subtropical gyres. They are detectable over multiple years and several thousand kilometers. Some anomalies are persistent enough to reach both the western boundary and equatorial current systems before being entirely eroded, and thus could form ocean “tunnels” equivalent to the well-studied atmospheric bridge to impact remote climate variability. Analysis of ocean tunnel propagation of a passive tracer (spice) and an active tracer (potential vorticity) confirms earlier model results that the active tracer decays more quickly than the passive tracer. Similarities and differences between timing and frequency of the two tracers could provide clues to anomaly formation mechanisms in various subduction regions. The success of ECCO in capturing these phenomena is encouragement to further explore their upstream sources and downstream impacts within this framework.

Predicting debris flow pathways using volume-based thresholds for effective risk assessment

Investigating the preferential flow path of a debris flow is crucial for quantifying the risk and developing mitigation strategies. Here, we examined 66 debris flows from the Western Ghats in India employing Rapid Mass Movement Simulation (RAMMS)::Debris Flow software to understand the kinematics of run-out. Our analysis revealed that the debris flow run-out in the study area follow two main routes: 60 along the existing stream channels (SC) and six following the steepest hill slope (SH). We further simulated these debris flows to identify their drivers, and derived a threshold that distinguishes between SC and SH-type debris flows. Our results indicate that the debris flow volumes greater than 7072 cu. m is SH-type, whereas those with smaller volumes are more likely to follow SC paths. The model’s accuracy was validated against field observations, achieving a success rate of 93% for SH-type flows and 85% for SC.

Polyaxial Stress-Dependent Tensorial Permeability Variations of a Columnar Jointed Rock Mass: Insights from 3D Distinct Element Method

AbstractStress-induced permeability changes in geological formations have implications for various geo-engineering applications. Fractures are the predominant fluid flow pathways within tight geological formations such as jointed basaltic rock mass. Three-dimensional permeability variations of a columnar jointed rock mass using the three-dimensional block distinct element method are investigated. First, a permeability tensor is constructed by simulating fluid flow through joint sets using cubic law and determining its principal components through eigenvector analysis. Subsequently, numerical simulations are conducted to gain insights into the impact of principal stresses on joint deformation and fluid flow. Joint deformation is controlled by the joint’s mechanical properties, contact models, and stress state. Different isotropic and anisotropic stress loading scenarios on the permeability tensor evolution are investigated. The research findings indicate that isotropic stress loading led to uniform normal compression on fractures, resulting in a monotonic reduction of all permeability tensor components and increased permeability anisotropy. Anisotropic stress loading, particularly the intermediate stress, often neglected, significantly influenced the rock’s overall permeability. While the directions of the principal components remained consistent during isotropic loading, they exhibited changes in both direction and magnitude during anisotropic loading. The relative angle between the joint plane and the principal stresses was crucial in controlling joint behavior, including normal compression, shear failure, and dilation. Additionally, data analysis revealed that the exponential empirical model provided an excellent fit for permeability–stress data.

Effects of (Assisted) Natural Regeneration on Infiltrability and Preferential Flow Pathways in the Khasi Hills (Meghalaya, NE India)

ABSTRACTIntensified slash‐and‐burn cultivation and forest clearing have caused severe land degradation in the Khasi Hills (Meghalaya plateau, NE India). Despite very high annual rainfall, the region faces severe water scarcity during the dry season. Local initiatives aim to restore forests through assisted natural regeneration (ANR) in this hydrologically poorly known area. As a first step towards assessing the potential hydrological impact of forest regrowth and ANR, we measured infiltrability at sites representing Imperata‐dominated grassland (n = 2, degraded baseline); < 20‐year‐old fallows with ANR (n = 3); semi‐mature to old‐growth forests (n = 4, near‐natural baseline); and a bench‐terraced Cryptomeria plantation. Group‐median infiltrability was highest in forests (425 mm h−1), followed by young fallows with ANR, and grasslands (145 and 68 mm h−1, respectively), and the terraced plantation (50 mm h−1). Infiltrability increased with regrowth age at an average rate of 3.0 mm h−1 y−1. Dye infiltration experiments were used to identify dominant percolation pathways per main land‐cover type. Infiltration in the least‐disturbed forest was dominated by flow along roots, stones and other preferential pathways, while matrix flow dominated in the grassland; the ANR site showed intermediate behaviour (macropore flow with high matrix interaction). Comparing median infiltrabilities with (maximum) hourly rainfall intensities suggested infiltration‐excess overland flow may occur occasionally in the grasslands. Despite improved infiltrability during regrowth (with or without ANR), the extreme monsoon rainfall and often shallow and stony soils pose serious limitations to rebuilding soil water storage capacity and favour frequent saturation‐excess overland flow.

Experimental Analysis of Elastic Property Variations in Methane Hydrate-Bearing Sediments with Different Porosities

Natural gas hydrates, a promising clean energy resource, hold substantial potential. Porosity plays a crucial role in hydrate systems by influencing formation processes and physical properties. To clarify the effects of porosity on hydrate elasticity, we examined methane hydrate formation and its acoustic characteristics. Experiments were conducted on sediment samples with porosities of 23%, 32%, and 37%. P- and S-wave velocities were measured to assess acoustic responses. Results show that as hydrate saturation increases, sample acoustic velocity also rises. However, high-porosity samples consistently exhibit lower acoustic velocities compared to low-porosity samples and reach a lower maximum hydrate saturation. This behavior is attributed to rapid pore filling in high-porosity samples, which blocks flow pathways and limits further hydrate formation. In contrast, hydrate formation in low-porosity sediments progresses more gradually, maintaining clearer pore channels and resulting in relatively higher hydrate saturation. Higher porosity also accelerates the shift of hydrates from cementing to load-bearing morphologies. These findings underscore porosity’s significant influence on hydrate formation and provide insights into observed variations in hydrate saturation and acoustic velocity across different experimental conditions.

A State-of-the-Art Review of Hydraulic Fracturing in Geothermal Systems

As a renewable and green energy source, geothermal energy holds tremendous developmental value. Hydraulic fracturing plays a significant role in enhancing geothermal energy extraction by improving reservoir permeability and creating pathways for fluid flow. Previous reviews have primarily focused on specific aspects of hydraulic fracturing, such as fracturing processes, cyclic hydraulic fracturing, and sustainability metrics, without comprehensively addressing the gaps in experimental and modeling approaches under real geothermal conditions. This work aims to bridge these gaps by summarizing the current studies on hydraulic fracturing methods, examining critical factors such as loading scheme, injection fluid, and rate, identifying limitations, and proposing potential solutions. Key findings reveal that rock temperature, sample size, and confining pressure significantly influence fracture propagation. However, laboratory experiments often fail to replicate field-scale conditions, particularly for temperatures exceeding 200 °C and for large rock samples. Numerical and theoretical models, although insightful, require further validation through experimental data. To address these limitations, this study suggests potential approaches suitable for hydraulic fracturing under real-world conditions, such as ultra-high-temperature, high-stress environments, and large-scale experiments, which are critical for advancing geothermal systems. This work can serve as a foundation for enhancing the efficiency and sustainability of geothermal energy extraction through hydraulic fracturing.

Effect of fracture parameters on the thermal recovery performance of enhanced geothermal system

ABSTRACT Enhanced geothermal system (EGS) is an effective method for extracting thermal energy from Hot Dry Rock (HDR) reservoirs. Fracture characterization determines the pathways for fluid flow and the mechanisms of heat transfer, both of which exert a substantial influence on the thermal recovery performance of EGS. This study develops a two-dimensional discrete fracture thermal-hydraulic (TH) coupled numerical model to investigate the influence laws of fracture characteristic parameters on the thermal recovery performance of EGS. The reliability of the numerical model is verified by comparison with the analytical method. Moreover, the Morris method is employed to evaluate the extent to which various system parameters affect the output temperature of EGS. The findings indicate that when the fracture opening expands from 0.5 mm to 3 mm, the output temperature decreases from 120.75°C to 94°C, while electrical output power increases; When the fracture permeability increases from 1 × 10−9 m2 to 4 × 10−9 m2, the output temperature drops by 30.7%, but the electrical output power increases by 0.98 MW. That is, with higher fracture opening and permeability, the fluid will flow inside the fracture with higher velocity, leading to a reduction in the output temperature of EGS and an increase in electrical output power; Injection temperature holds the greatest influence on the system, while the system’s output temperature demonstrates insensitivity to the variation of rock permeability.

The Effects of Facies Variability and Bioturbation Intensity on Permeability in a Mixed Siliciclastic–Carbonate Core from the Upper Strawn Group, Katz Field, Eastern Shelf of the Permian Basin, Texas, USA

For oil and gas reservoir characterization, permeability prediction is indispensable because it helps identify potential flow pathways and lowers risk. Estimating permeability in heterogeneous media is challenging due to the limited number of measurement tools, low-resolution sampling methods, and sampling bias. To combat these issues, we employed a probe permeameter to produce a high-resolution (4 in [10 cm] spacing) permeability dataset for cores from the Strawn Formation, Katz Field, Permian Basin, Texas, USA. We structured our sampling to record permeability changes related to facies variability and fluctuating bioturbation intensity. We compared probe permeameter data to wireline logs and core-plug porosity and permeability data recorded at larger spacings. The results show that permeability is affected by facies type, bioturbation intensity, and cementation. The effects of bioturbation are non-linear; in our study, moderate bioturbation enhances permeability by improving connections between sands while intense bioturbation decreases permeability by redistributing fines. Core-plug and probe measurements gave similar permeability values, but the number of core plugs taken in the finer-grained intervals was insufficient. The probe, however, provided better resolution and gave larger net-to-gross sand ratios than core-plug-based evaluations. Using only the core-plug porosity–permeability relationship with wireline density log porosities led to permeability predictions too large by a factor of three or more compared to averaged probe permeameter values.

Zinc isotopes trace the metal source and fluid flow pathways of the large Caixiashan Pb–Zn deposit, China

Zinc isotopes trace the metal source and fluid flow pathways of the large Caixiashan Pb–Zn deposit, China

Multiscale Pore Architecture and Its Influence on Porosity, Permeability, and Fluid Flow in Tight Gas Reservoirs of the Shihezi H8 Formation, Ordos Basin

Characterizing pore network morphology and its influence on critical reservoir properties such as porosity, permeability, and fluid flow pathways is imperative for maximizing production from tight gas sandstone reservoirs. This study integrated petrographic and pore-scale analyses to investigate diagenetic effects on the Shihezi H8 Formation, Ordos Basin, China. Sixty core plug samples spanning depositional facies from wells were analyzed using thin-section petrography, scanning electron microscopy, laser grain size analysis, mercury injection capillary pressure (MICP), nuclear magnetic resonance (NMR), and porosity–permeability measurements. Thin-section observations indicated that formation primarily comprises litharenite and sub-litharenite sandstones deposited in fluvial–deltaic environments composed primarily of quartz and feldspar grains. Diagenesis caused significant porosity reduction through initial mechanical compaction, 3–13% quartz cementation, and localized dissolution, resulting in secondary porosity of up to 5%. Three diagenetic facies were differentiated based on variations in mineralogy and diagenetic alterations. MICP classified pore networks into three reservoir types defined by mean throat radii ranging from 0.091 to 0.270 μm. NMR distinguished pore architectures as uniformly microporous, bimodally micro–mesoporous, and heterogeneously distributed multiscale pores. Larger throat radii correlated positively with higher porosity (up to 8.6%), gas porosity (10.5%), and permeability (0.1911 mD). Grain size analysis demonstrated a positive correlation between mean detrital grain diameter (>2.6 φ, 0.18 mm, (180 µm)), and significantly elevated average porosity (5–8%) compared to finer lithologies, implying depositional energy and sorting regimes. Integrating depositional features, diagenetic alterations, and multiscale pore architecture characterization quantitatively and qualitatively enhanced predictions of heterogeneity in hydrocarbon flow behavior amongst these tight reservoirs. The optimized insights from this integrated study provide a framework to guide development strategies and field appraisal methods for maximizing recovery from unconventional tight gas formations.

Exploring the Molecular Weight Effects of Poly(isobutylene) (PIB) in Slurry-Cast NMC811 Cathode for the Development of Sulfide Solid-State Batteries

Sulfide-based solid-state battery emerges as the next generation of traditional lithium-ion battery with liquid electrolyte due to high room temperature ionic conductivity of sulfide electrolyte (eg. Halide substituted argyrodite, LPSCl at 1 mS/cm) and inherent safety. However, the production of high-performance thin film cathodes continues to be a significant hurdle. Such cathodes are typically processed by mixing cathode active material (CAM) and solid electrolyte, with an optimal ratio of 50 vol% to ensure the ionic percolation1, followed by tape casting. To fulfill the manufacture purpose, binder was often introduced in the cathode to further improve its mechanical integrity for large scale battery’s production. However, binder in cathode designs impede cell performance due to their non-conductive nature, blocking the pathways for electron and ion flow, as evidenced in many reports2-4.Herein, we assess the impact of Poly(isobutylene) (PIB), a non-polar binder, with different molecular weights (low, medium, and high kg/mol values, denoted as L_PIB, M_PIB, H_PIB) at 2 wt% loading on the mechanical strength and electrochemical performance of slurry-cast LiNi0.82Mn0.07Co0.11O2 (NMC811) cathodes in full cells. Prior study indicated molecular weight of binder affects the structural cohesion of the electrodes and cycling performance5. In this study, we use slurry-casting to process our cathodes instead of pellet-type traditional dry pressing because its scalability and its ability to ensure a uniform distribution of active materials. Our full cell testing reveals that the cell with H_PIB-cathode exhibits ~44% of discharge capacity in average higher than L_PIB-cathode at discharging rate of 1.6 mAh cm-2. This possibly indicates H_PIB-cathode possesses harden-straining property which allows strong adhesion between NMC 811 and LPSCl particles. H_PIB-cathode outperforms L_PIB-cathode in terms of capacity retention (88% over 70 cycles vs. 77% over 60 cycles), which is potentially attributed to higher molecular weight PIB in cathode protecting the crack formation over cycling.These electrochemical results are further elucidated by: 1) Galvanostatic intermittent titration technique (GITT) to quantify the apparent diffusion coefficient in cathode; 2) Scanning electron microscopy (SEM) to examine the particles distribution and morphology; 3) Raman spectroscopy (RS) to detect the change of chemical composition in cathode interphase. Acknowledgement This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) in the Vehicle Technologies Office (VTO) through the Advanced Battery Materials Research (BMR) Program, managed by Drs. Simon Thompson and Tien Duong. EW would acknowledge the support from the Advanced Materials and Manufacturing Technologies Office (AMMTO) of the EERE through its summer internship program. SEM and AFM research was conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. We thank Dr. Thomas A. Zawodzinski, Dr. Anna Mills and Dr. Daniel Hallinan for fruitful discussions.References Minnmann, P.; Strauss, F.; Bielefeld, A.; Ruess, R.; Adelhelm, P.; Burkhardt, S.; Dreyer, S. L.; Trevisanello, E.; Ehrenberg, H.; Brezesinski, T.; Richter, F. H.; Janek, J., Designing Cathodes and Cathode Active Materials for Solid-State Batteries. Advanced Energy Materials 2022, 12 (35), 2201425.Teo, J. H.; Strauss, F.; Tripković, Đ.; Schweidler, S.; Ma, Y.; Bianchini, M.; Janek, J.; Brezesinski, T., Design-of-experiments-guided optimization of slurry-cast cathodes for solid-state batteries. Cell reports physical science 2021, 2 (6), 100465.Bielefeld, A.; Weber, D. A.; Janek, J. r., Modeling Effective Ionic Conductivity and Binder Influence in Composite Cathodes for All-Solid-State Batteries. ACS applied materials & interfaces 2020, 12 (11), 12821-12833.Nam, Y. J.; Oh, D. Y.; Jung, S. H.; Jung, Y. S., Toward practical all-solid-state lithium-ion batteries with high energy density and safety: Comparative study for electrodes fabricated by dry- and slurry-mixing processes. Journal of power sources 2018, 375, 93-101.Hu, B.; Shkrob, I. A.; Zhang, S.; Zhang, L.; Zhang, J.; Li, Y.; Liao, C.; Zhang, Z.; Lu, W.; Zhang, L., The existence of optimal molecular weight for poly(acrylic acid) binders in silicon/graphite composite anode for lithium-ion batteries. Journal of power sources 2018, 378 (C), 671-676.

Unintended consequences of modifying coastal river systems

Coastal infrastructure projects, particularly the modification of coastal river channels, are becoming increasingly significant to economic activities worldwide as a response to climate-driven changes and urbanization. The benefits of channel modification projects can be realized quickly, but the altered movement of sediments in the river channel can lead to unintended geomorphic changes years or decades later. An example of this is the closure of the San Bernard River mouth, located on the central coast of Texas, which was clogged with sediments by the 1990s as a result of two major projects in the area: the diversion of the Brazos River channel (1929) and the construction of the Gulf Intracoastal Waterway (GIWW) (1940s). The objective of this study was to a) document the delayed geomorphic response to the projects using a GIS analysis of historical maps and aerial imagery, and b) provide a snapshot of altered flow pathways in the area using measurements collected in situ. Results showed that the GIWW was the main conduit for river flow as it bisects the San Bernard River 2 km inland of its river mouth, reducing discharge in the terminal limb of the river. Due to reduced flow, the river mouth became clogged with wave-transported sediment supplied by the still-adjusting Brazos River which had been diverted to within 6 km of the San Bernard River. With a limited connection to the sea, altered sediment and flow pathways have led to numerous hazards and costly corrective dredging projects surpassing $12 million to date. Optimizing the cost-effectiveness of channel modification projects requires considering their long-term impact as managers continue to adapt to ever-changing coastal zones.

Evolution of Auriferous Fluids in the Kraaipan-Amalia Greenstone Belts: Evidence from Mineralogical and Isotopic Constraints

The Kraaipan and Amalia greenstone belts in South Africa occur in the western part of the Kaapvaal Craton. The two belts stretch discontinuously in an approximately north–south orientation over a distance of about 250 km from southern Botswana in the north to the Vaal River near Christiana in the south and are separated by a distance of about 90 km. Gold mineralization is hosted in banded iron formation at both the Kalahari Goldridge deposit (Kalgold) in the Kraaipan greenstone belt in the north and the Amalia deposit in the Amalia greenstone belt in the south, with the mineralization associated with quartz–carbonate veins. The footwalls of these deposits are generally composed of mafic volcanic schist and the hanging walls consisting of graywackes, schist and shale units. The Kalgold and Amalia gold deposits show some variation in the redox condition of the mineralizing system and fluid chemistry. The ore mineral assemblage is characterized by magnetite–pyrrhotite–pyrite at Kalgold, which is indicative of reducing conditions, and a magnetite–hematite–pyrite assemblage at Amalia that suggests a relatively oxidizing environment. Average mineralizing temperatures determined from chlorite geothermometry were relatively higher at the Kalahari Goldridge deposit ranging from 350 to 400 °C compared to the slightly cooler range of 330 to 390 °C at Amalia. The composition of the fluids derived from fluid inclusions is indicative of low salinity H2O--CO2±CH4-rich fluids at Kalgold against relatively H2O-CO2-rich fluids at Amalia. Evidence from strontium–carbon–oxygen isotopic ratios from carbonates suggests that differences in redox conditions in the deposits could be attributed to different flow pathways by an evolving fluid from a common source (with minimum 87Sr/86Sr = 0.70354) to the sites of gold deposition, with a significant ore fluid interaction with a thick sequence of carbonaceous meta-pelitic rock units at the Kalahari Goldridge deposit that is absent in the Amalia deposit.

Characterization of Groundwater Geochemistry in an Esker Aquifer in Western Finland Based on Three Years of Monitoring Data

This study investigated the hydrogeochemistry of a shallow Quaternary sedimentary aquifer in an esker deposition in western Finland, where distinct spatial and temporal variability in groundwater hydrogeochemistry has been observed. Field investigation and hydrogeochemical data were obtained from autumn 2010 to autumn 2013. The data were analyzed using the multivariate statistical methods principal component analysis (PCA) and hierarchical cluster analysis (HCA), in conjunction with groundwater classification based on the main ionic composition. The stable isotope ratios of δ18O and δD were used to determine the origin of the groundwater and its connection to surface water bodies. The groundwater geochemistry is characterized by distinct redox zones caused by the influence of organic matter, pyrite oxidation, and preferential flow pathways due to different hydrogeological conditions. The groundwater is of the Ca-HCO3 type and locally of the Ca-HCO3-SO4 type, with low TDS, alkalinity, and pH, but elevated Fe and Mn concentrations, KMnO4 consumption, and, occasionally, Ni concentrations. The decomposition of organic matter adds CO2 to the groundwater, and in this study, the dissolution of CO2 was found to increase the pH and enhance the buffering capacity of the groundwater. The mobility of redox-sensitive elements and trace metals is controlled by pH and redox conditions, which are affected by the pumping rate, precipitation, and temperature. With the expected future increases in precipitation and temperature, the buffering capacity of the aquifer system will enhance the balance between alkalinity from bioactivity and acidity from recharge and pyrite oxidation.

Cavity induced modulation of intramolecular vibrational energy flow pathways.

Recent experiments in polariton chemistry indicate that reaction rates can be significantly enhanced or suppressed inside an optical cavity. One possible explanation for the rate modulation involves the cavity mode altering the intramolecular vibrational energy redistribution (IVR) pathways by coupling to specific molecular vibrations in the vibrational strong coupling (VSC) regime. However, the mechanism for such a cavity-mediated modulation of IVR is yet to be understood. In a recent study, Ahn et al. [Science 380, 1165 (2023)] observed that the rate of alcoholysis of phenyl isocyanate (PHI) is considerably suppressed when the cavity mode is tuned to be resonant with the isocyanate (NCO) stretching mode of PHI. Here, we analyze the quantum and classical IVR dynamics of a model effective Hamiltonian for PHI involving the high-frequency NCO-stretch mode and two of the key low-frequency phenyl ring modes. We compute various indicators of the extent of IVR in the cavity-molecule system and show that tuning the cavity frequency to the NCO-stretching mode strongly perturbs the cavity-free IVR pathways. Subsequent IVR dynamics involving the cavity and the molecular anharmonic resonances lead to efficient scrambling of an initial NCO-stretching overtone state over the molecular quantum number space. We also show that the hybrid light-matter states of the effective Hamiltonian undergo a localization-delocalization transition in the VSC regime.

Abstract 4117646: The Ultimate Test in Hemocompatibility: HeartMate3 Restart After Prolonged Pump Shut Down

Introduction: The HeartMate 3 (HM3) LVAD, was shown to have a higher survival free of hemocompatibility related adverse events (HRAE) compared to its predecessors (HM2, HVAD). Superior HM3 outcomes are attributed to wide blood flow pathways coupled with frictionless movement and intrinsic pulsatility, reducing shear stress and blood stasis. It is unknown if improved hemocompatibility can withstand pump restart after prolonged shutdown. We herein report a case of HM3 pump stoppage without subsequent HRAE. Case Presentation: A 41-year-old male underwent HVAD implant in 2019 for advanced non-ischemic cardiomyopathy. This was exchanged to HM3 for recurrent neurological events despite therapeutic anticoagulation. Ten months after exchange, he awakened one morning to find his LVAD had been off for an unknown period but had not heard any device alarms (85dB if on battery power, 165dB if on wall power). Since he felt well he changed to battery power resulting in immediate pump restart. Log file analysis showed pump stoppage 2 am – 10 am, without preceding low flow alarms or power elevations. Management and Outcomes: In the ER INR was 1.5 (2.8 one week prior) and systemic heparin was started. Evaluation included: 1) CT brain without acute infarcts 2) echocardiogram without intracardiac thrombus 3) CT Angiography with patency of the inflow cannula and outflow graft 4) stable serial LDH measurements. The controller was exchanged, and analysis noted normal function. 1-year later the patient is maintained on warfarin and aspirin 325mg without further HRAE. Given the patient’s neurologic history and pump stoppage event, we did not invoke ARIES trial guidance and thus continued aspirin. Conclusion: Pump stoppage occurs when there is complete battery depletion, disconnection of both power leads, or the percutaneous lead from system controller. Our case is unique in that the duration of pump shutdown was 8 hours and INR subtherapeutic, without HRAE in the background of neurologic events on HVAD support. It has been previously reported that complete outflow graft thrombosis can occur shortly after LVAD decommissioning. The HM3 User Manual recommends restarting the pump immediately if off for a few minutes and using clinical judgment for longer durations due to increased risk for thromboembolic events. Our case adds to the paucity of existing data on improved hemocompatibility of the HM3 during rare circumstances of the ultimate test in hemocompatibility: complete pump shut down.

Using geochemical and geophysical data to characterise inter-aquifer connectivity and impacts on shallow aquifers and groundwater dependent ecosystems

Understanding inter-aquifer connectivity within sedimentary basins is crucial for determining how groundwater extraction will impact groundwater resources and groundwater dependent ecosystems (GDEs). Geophysical, geochemical and radioisotope data were combined to understand whether dewatering for open-cut coal mining in Australia's Galilee Basin will be likely to impact groundwater levels in overlying aquifers sustaining the ecologically significant Doongmabulla Springs Complex and Carmichael River. Groundwater salinities (<300 mg/L), measurable 3H (0.43 TU), and activities of radiocarbon a14C (14.1 – 95.3 pMC) and chlorine-36 R36Cl (78.1 × 10−15 – 161 × 10−15) imply that preferential pathways for groundwater flow and recharge occur through the weathered sub-crop of the Galilee Basin sediments. These high permeability zones occur consistently within 5 km of the mine (and further to the south), where strong overlap in major ion and radioisotope compositions indicates significant groundwater connectivity between aquifers. Elevated groundwater HCO3 and F concentrations and heavy fraction hydrocarbons (>100 μg/L C10–C40) also imply deep groundwater in the coal measures discharges into overlying non-coal bearing aquifers, most likely via faults. Since coal mine dewatering commenced, drawdown has spread preferentially southward from the mine, driven by geological heterogeneity including into aquifers that are not targeted by mining. Drawdown is also migrating gradually into shallow aquifers west of the mine, towards GDEs along the Carmichael River valley. Numerical modelling of the mine's groundwater impacts, which was the basis of the mine's approval, did not anticipate this level of drawdown in shallow aquifers at this stage of mining. Mining impacts on shallow groundwater resources and GDEs, including the Doongmabulla springs and the Carmichael River, may have thus been underestimated and require re-evaluation. This study highlights that multiple lines of evidence must be assessed to carefully develop conceptual and numerical models, and to protect groundwater and GDEs.

Encoding of Global Visual Motion in the Avian Pretectum Shifts from a Bias for Temporal-to-Nasal Selectivity to Omnidirectional Excitation across Speeds.

The pretectum of vertebrates contains neurons responsive to global visual motion. These signals are sent to the cerebellum, forming a subcortical pathway for processing optic flow. Global motion neurons exhibit selectivity for both direction and speed, but this is usually assessed by first determining direction preference at intermediate velocity (16-32°/s) and then assessing speed tuning at the preferred direction. A consequence of this approach is that it is unknown if and how direction preference changes with speed. We measured directional selectivity in 114 pretectal neurons from 44 zebra finches (Taeniopygia guttata) across spatial and temporal frequencies, corresponding to a speed range of 0.062-1,024°/s. Pretectal neurons were most responsive at 32-64°/s with lower activity as speed increased or decreased. At each speed, we determined if cells were directionally selective, bidirectionally selective, omnidirectionally responsive, or unmodulated. Notably, at 32°/s, 60% of the cells were directionally selective, and 28% were omnidirectionally responsive. In contrast, at 1,024°/s, 20% of the cells were directionally selective, and nearly half of the population was omnidirectionally responsive. Only 15% of the cells were omnidirectionally excited across most speeds. The remaining 85% of the cells had direction tuning that changed with speed. Collectively, these results indicate a shift from a bias for directional tuning at intermediate speeds of global visual motion to a bias for omnidirectional responses at faster speeds. These results suggest a potential role for the pretectum during flight by detecting unexpected drift or potential collisions, depending on the speed of the optic flow signal.

Validating a Calibrated Model of a Groundwater Pump-And-Treat System Using Robust Multiple Regression

Validation of groundwater models is relatively challenging due to the need to reserve scarce water level data for calibration targets. In addition, traditional statistical validation metrics are unintuitive for non-technical audiences and do not directly identify model behaviors that require further refinement. We developed a novel model validation method that analyzes rate change events at pump-and-treat wells and statistically compares the water level responses at nearby monitoring wells between the data and model. The method takes advantage of events that occur alongside ambient pumping, unlike parameter estimation techniques that require independent drawdown or recovery events. The ability of the model to match well connections that are evident (or not evident) in the observations is characterized statistically, leading to four decision scenarios: model matches the observed connection (1) or lack thereof (2), model exhibits a connection that is not observed (3), or model over- or understates the observed connection (4). The method is applied to an FEHM-based groundwater flow and transport model that is shown to match 84.5% of the well connections analyzed. The method provides novel perspectives on the influence of calibration targets on the flow field and suggests that although the overall effect of drawdown targets was to improve the model, the choice of target well pairs creates flow pathways that may be inconsequential during normal operational conditions. The model adequately matches the flow over short spatial scales (&lt;800 m) and over-represents the flow over greater distances (300–1200 m), suggesting the need for “null” drawdown targets in subsequent rounds of calibration.

Experimental investigation on fracture propagation in shale fractured by high-temperature carbon dioxide

The productivity of shale reservoirs was significantly enhanced by the high-temperature CO2 fracturing technique. The injection of high-temperature CO2 into the formation induced rock fracture propagation, creating advantageous pathways for fluid flow. In this research, a self-developed in situ high-temperature convective heat simulation experimental apparatus was employed to systematically conduct simulated experiments on high-temperature CO2 fractured shale under different influencing factors. The experimental results demonstrated that the permeability of CO2 increased as the injection temperature increased. The rock fracture pressure was effectively reduced by high-temperature CO2 fractured shale. Higher complexity was observed in fracture propagation, accompanied by a substantial increase in microcracks and branching fractures. The shale fracture pressure increased with increasing triaxial stress and CO2 injection rate. The confining pressure restricted the further propagation of fractures under relatively high stress conditions, thereby reducing the width and density of fractures, lowering the fracture complexity. Nevertheless, the thermal shock effect of the fluid was exacerbated as the injection rate of high-temperature CO2 increased. The initiation of microcracks was facilitated by the intensification of local thermal stress in shale, inducing multiple curved fractures and forming a more complex fracture network. Compared to horizontal bedding shale, the fracture pressure of vertical bedding shale was relatively higher during high-temperature CO2 fracturing. In addition, the geometric morphology of fracture propagation was more complex, characterized by rougher fracture surfaces, leading to a greater improvement in reservoir reconstruction volume. This research contributed to the optimization of CO2 resource utilization, provided experimental evidence for the application of high-temperature convection fracturing technology in in situ shale conversion projects.