Incision Rates Research Articles

Insights into the synergistic effects of tectonics and climate from the formation and evolution of the Hongwen allochthonous deposit, southwestern China

Abstract The formation and evolution of large-scale deposits generated by mass movement are often closely related to tectonic and climatic conditions. Investigating deposits under the influence of complex geological conditions can aid in reconstructing paleoenvironmental characteristics and fluvial geomorphic evolution. The First Bend of the Yangtze River (FBYR), located in the Jinsha River basin in southwest China, represents a significant section characterized by abundant allochthonous deposits. We conducted a detailed investigation of the Hongwen allochthonous deposit (HAD) and the river sediments in the First Bend. Through terrain interpretation, dating, and paleoenvironmental analysis, the HAD was determined to be a complex deposit with multiple sources and stages (46.4–33.5 ka), formed under the combined influence of tectonic activity and climate. Three mass-movement events occurred during the interglacial stage of the last glacial period or its transitional period, coinciding with the rapid uplift stage of the Tibetan Plateau since the late Pleistocene. Prominent features of this period include significant rainfall and tectonic activities. By dating fluvial sediments and examining the evolution of the HAD, we revealed a river incision rate of 2.30 mm/yr for the Jinsha River, providing a basis for analyzing periodic river cutting and the development pattern of surface processes.

Topographic metrics for unveiling fault segmentation and tectono-geomorphic evolution with insights into the impact of inherited topography, Ulsan Fault Zone, South Korea

Abstract. Quantifying today's topography can provide insights into landscape evolution and its controls, since present topography represents a cumulative expression of past and present surface processes. The Ulsan Fault Zone (UFZ) is an active fault zone on the southeastern Korean Peninsula that was reactivated as a reverse fault around 5 Ma. The UFZ strikes NNW–SSE and dips eastward. This study investigates the relative tectonic activity along the UFZ and the landscape evolution of the hanging-wall side of the UFZ, focusing on neotectonic perturbations using 10Be-derived catchment-averaged denudation rates and bedrock incision rates, topographic metrics, and a landscape evolution model. Five geological segments were identified along the fault, based on their relative tectonic activity and fault geometry. We simulated four cases of landscape evolution to investigate the geomorphic processes and accompanying topographic changes in the study area in response to fault movement. Model results reveal that the geomorphic processes and the patterns of topographic metrics (e.g., χ anomalies) depend on inherited topography (i.e., the topography that existed prior to reverse fault reactivation of the UFZ). On the basis of this important model finding and additional topographic metrics, we interpret the tectono-geomorphic history of the study area as follows: (1) the northern part of the UFZ has been in a transient state and is in topographic and geometric disequilibrium, so this segment underwent asymmetric uplift (westward tilting) prior to reverse faulting on the UFZ around 5 Ma, and (2) its southern part was negligibly influenced by the asymmetric uplift before reverse faulting. Our study demonstrates the utility of topographic metrics as reliable criteria for resolving fault segments. Together with landscape evolution modeling, topographic metrics provide powerful tools for examining the influence of inherited topography on present topography and for the elucidation of tectono-geomorphic histories.

Modeling Climate and Tectonic Controls on Bias in Measured River Incision Rates

AbstractRates of land surface processes provide insights into climatic and tectonic influences on topography. Bedrock incision rates are estimated by dating perched landforms such as strath terraces, assuming a constant bedrock incision rate from terrace abandonment to the next terrace level or present river level. These estimates express biases from the stochastic nature of sediment and water discharge in controlling river incision as well as from using a mobile channel elevation as a reference frame, leading to different incision rates when calculated over different timeframes. We introduce a 1‐D model incorporating fluvial mechanics, tectonics, sediment, and climate variability to predict these biases and assess their sensitivity to climate and tectonics. Findings suggest biases intensify under highly variable climates and slow rock uplift, with climate periodicity being a primary control for our modeled scenarios. Our model provides a mechanism to improve river incision measurement uncertainty, impacting paleoclimate and tectonic geomorphology reconstructions.

Intensive Care Unit Transfer in Patients With Deep Neck Infections.

Background: Deep neck infection (DNI) involves the deep neck spaces and may lead to airway compromise. An intensive care unit (ICU) is a specialized unit of the hospital that provides intensive care. ICU care is required for patients with severe DNI, although the risk factors for need of ICU care in patients with DNI have not been investigated. Methods: The clinical and laboratory parameters of 350 patients aged >18 years who were diagnosed with DNI between October 2018 and October 2023 were evaluated. Of these patients, 62 were transferred to the ICU. Univariate and multivariate analyses were applied to assess the risk factors for need of ICU care. Results: Univariate analysis revealed that older age [odds ratio (OR) = 1.0324, 95% confidence interval (CI): 1.0155-1.0496, P = .0001], a higher C-reactive protein (CRP) level (OR = 1.0076, 95% CI: 1.0049-1.0103, P < .0001), and blood glucose level (OR = 1.0057, 95% CI: 1.0023-1.0091, P = .0011), involvement ≥3 spaces (OR = 2.2366, 95% CI: 1.2827-3.8998, P = .0046), and mediastinitis (OR = 4.7134, 95% CI: 2.3537-9.4391, P < .0001) were significant risk factors for ICU transfer in patients with DNI. In multivariate analysis, older age (OR = 1.0216, 95% CI: 1.0032-1.0403, P = .0210), higher CRP level (OR = 1.0063, 95% CI: 1.0033-1.0092, P < .0001), and mediastinitis (OR = 2.6103, 95% CI: 1.1974-5.6905, P = .0158) were independent risk factors of ICU transfer in patients with DNI. The ICU group had a longer hospital stay (23.98 ± 8.53 vs 7.44 ± 4.24, P < .0001) and higher rate of tracheostomy (P < .0001) than the non-ICU group. However, there were no significant differences in the rate of incision and drainage open surgery or pathogens between the groups (all P > .05). Conclusions: Elder patients and those with advanced CRP levels and mediastinitis are more likely to be transferred to the ICU, leading to prolonged hospital stays and a higher risk of tracheostomy. Clinicians should assess the patient's need for ICU transfer and timely manage the airway according to the aforementioned laboratory parameters and complications carefully.

Using Disorder Metrics to Distinguish Discharge‐Driven From Drainage Area‐Driven Incision and Quantify Deviations in Channel Steepness

AbstractThe rate of channel incision in bedrock rivers is often described using a power law relationship that scales erosion with drainage area. However, erosion in landscapes that experience strong rainfall gradients may be better described by discharge instead of drainage area. In this study, we test if these two end member scenarios result in identifiable topographic signatures in both idealized numerical simulations and in natural landscapes. We find that in simulations using homogeneous lithology, we can differentiate a posteriori between drainage area and discharge‐driven incision scenarios by quantifying the relative disorder of channel profiles, as measured by how well tributary profiles mimic both the main stem channel and each other. The more heterogeneous the landscape becomes, the harder it proves to identify the disorder signatures of the end member incision rules. We then apply these indicators to natural landscapes, and find, among eight test areas, no clear topographic signal that allows us to conclude a discharge or area‐driven incision rule is more appropriate. We then quantify the distortion in the channel steepness index induced by changing the incision rule. Distortion in the channel steepness index can also be driven by changes to the assumed reference concavity index, and we find that distortions in the normalized channel steepness index, frequently used as a proxy for erosion rates, is more sensitive to changes in the concavity index than to changes in the assumed incision rule. This makes it a priority to optimize the concavity index even under an unknown incision mechanism.

Unraveling the tectonic and climatic influences on River Erosion: A late Quaternary case from the Dongda River, northeast tibet

Rivers adjust their equilibrium profiles to base-level changes induced both by climatic fluctuations and tectonic movements. It is crucial, yet challenging, to differentiate their distinct roles in shaping the evolution of fluvial systems when both forces are involved. In contrast to the broader, regional-scale impact of climatic changes, the various tectonic deformation at local-scale can be recorded as various terrace deformation patterns. The Dongda River, located on the northeastern edge of the Tibetan Plateau, crosses active folds and thrusts, providing a unique opportunity to isolate the effects of climatic and tectonic forces. In this study, we identified five river terraces along Dongda River, designated as T1, T2, T3, T4a, and T4b, from lowest to highest. Radiocarbon and OSL dating results reveal abandonment ages of 4.2 ± 0.3 ka, 6.1 ± 0.5 ka, 12.4 ± 2.5 ka, 16.4 ± 0.2 ka, and 27.4 ± 2.5 ka, showing rhythmic alignment with climatic fluctuations since the late Pleistocene. Elevation profiles of the terraces demonstrate base-level aggradation at the footwall of the Fengle fault between T4a/b and T2, highlighting a tectonically dominated process of river incision at its hanging wall. Differential uplift rates were estimated to be 2.2 ± 0.3 mm/a at the North Qilian Shan hinterland, 1.1 ± 0.2 mm/a in the Huangcheng Basin, 0.2–0.4 mm/a in the Yangxiang Basin, and 1.1 ± 0.2 mm/a within the foreland fold-and-thrust belt of Dahuang Shan, respectively. In contrast, an accelerated incision rate (>1.8 mm/a) has been observed throughout the entire basin since the abandonment of T2, coinciding with the adjustments in the Asian monsoon and westerlies systems since the Mid-Holocene. This study provides insights into the complex interplay between climatic variability and tectonic activity in fluvial systems, enhancing our understanding of how these competing forces have shaped the evolution of the fluvial landscape over time.

Climatically-driven development of late Quaternary fluvial geomorphology in the arid inland of Asia

The forcing mechanism behind river incision and terrace formation is one of hot topics in the study of fluvial geomorphology. This work focused on the late Quaternary alluvial sequence in the south piedmont of the Chinese Altay Shan in the arid inland of Asia. In order to reveal the mechanism controlling the development of late Quaternary fluvial features along the mountain front, we conducted detailed fluvial geomorphological investigations on eight rivers, including geomorphic mapping, optically stimulated luminescence (OSL) dating, and differential global position system (dGPS) surveying. By utilizing the Monte Carlo simulation with terrace data, the late Quaternary rates of river incision along the south piedmont of the Chinese Altay Shan were determined. The results show that (1) the terraces developed by the piedmont rivers are not more than four levels and the depth of river incision in the piedmont is only dozens of meters, with deeper valleys displayed by the western piedmont rivers; (2) terrace alluviums along the mountain front were accumulated during glacial stages, and the subsequent incision occurred during interglacial stages; (3) the rate of river incision was accelerated during the Holocene, when the regional climate was characterized by progressively increasing wetness. When combining with the regional tectonic setting, we propose that the climate could have played the key role in driving the alluvial accumulation and the subsequent incision in the south piedmont of the Chinese Altay Shan during the late Quaternary. Together with the similar observations from the northeastern margin of the Tibetan Plateau and the Tian Shan, we further propose that climatically-driven fluvial geomorphological development could be a common phenomenon during the late Quaternary in the arid interior of Asia.

Big Disaster from Small Watershed: Insights into the Failure and Disaster-Causing Mechanism of a Debris Flow on 25 September 2021 in Tianquan, China

The occurrence of debris flow events in small-scale watersheds with dense vegetation in mountainous areas that result in significant loss of life and missing individuals challenges our understanding and expertise in investigating and preventing these disasters. This has raised concerns about the occurrence of large debris flow disasters from small watersheds. This study focused on a catastrophic debris flow that took place in Longtou Gully (0.45 km2) in Tianquan County, Ya’an City on 25 September 2021, which resulted in 14 deaths and missing individuals. Through comprehensive field investigations, high-precision remote sensing data analyses, and numerical simulations, we analyzed the triggering mechanisms and dynamic processes of this event. Our results indicate that the convergence hollow at the channel head exhibited higher hydraulic conditions during rainfall compared to gentle slopes and convex terrains, leading to the instability of colluvial soil due to the expansion of the saturated zone near the soil–bedrock interface. The entrainment of material eroded from the channel resulted in an approximately 4.7 times increase in volume, and the channel scarp with a height of about 200 m amplified the destructive power of the debris flow. We emphasize the need to take seriously the possibility of catastrophic debris flows in small-scale watersheds, with colluvial deposits in hollows at the channel head under vegetation cover that serve as precursor material sources, and the presence of channel scarps formed by changes in the incision rate of the main river, which is common in the small watershed on both sides. This study provides insights for risk assessment of debris flows in small-scale catchments with dense vegetation cover in mountainous areas, highlighting the importance of vigilance in addressing disasters in small-scale catchments, particularly in regions with increasing human–environment conflicts.

Grain Size in Landscapes

Earth's terrestrial topography evolves in response to the interaction of tectonics, climate, and lithology. Recent discoveries suggest that the grain size of sediments produced on hillslopes and transported through river networks is key to understanding these interactions. Hillslope grain size varies systematically with erosion rate and residence time, the degree of chemical and physical weathering, and the fracture density and susceptibility to weathering of rock. Variations in initial grain size strongly influence the spatial evolution of grain size distributions as particles mix and wear during downstream transport through channel networks. In rivers, the size and flux of the coarse fraction of the sediment load control the rate of incision into bedrock and thus govern channel slope and ultimately the relief of actively eroding landscapes. These relationships suggest that a primary way that tectonics, climate, and lithology influence landscape evolution is through their controls on sediment grain size. ▪Recent research reveals the central role of sediment grain size in controlling bedrock river morphodynamics, linking grain size to channel slope and topographic relief.▪Tectonics, climate, and lithology govern the size of sediments produced on hillslopes; hence, grain size mediates their influence on landscape evolution.▪Feedbacks linking sediment grain size, topography, weathering, erosion, and sediment transport provide new opportunities for advances in Earth surface science.

Treatment of the Buried Bumper Syndrome​​​​​: A Retrospective Multicenter Study With Inclusion of 160 Cases.

The therapy of buried bumper syndrome (BBS) is difficult. The aim of this retrospective multicenter study was to analyze the treatment methods with focus on effectiveness and safety of endoscopic techniques. The analysis of all therapies and a comparison of the papillotome technique (PT) and needle knife-based nonpapillotome technique (NPT) were performed. Primary endpoint was technical success in one session, secondary endpoints overall technical success, number and duration of treatment sessions, SAE, and mortality. The primary treatment of 160 BBS cases, diagnosed between 2003 and 2021, was NPT in 60 (37.5%), PT in 43 (26.9%), push/pull technique (PPT) in 40 (25.0%), no removal in 9 (5.6%), laparotomy in 7 (4.4%) cases, and external incision in 1 (0.6%) case. For PT and NPT rates of technical success in one session were 95.5% and 45.0% (P<0.01), rates of overall technical success 100% and 88.3% (P=0.02), and mean number and duration of treatment sessions 1.05 (±0.21) versus 1.70 (±0.91) (P<0.01) and 32.17 (±21.73) versus 98,00 (±62.28) minutes (P<0.01), respectively. No significant differences between PT and NPT were found for SAE (15.9% vs. 25.0%) and mortality (2.3% vs. 1.7%). For PPT, laparotomy and external incision rates of technical success in one session and overall technical success were 100%, rates of SAE 2.5%, 50.0%, and 0% and mortality 0%, 10.0%, and 0%. Endoscopic therapy of BBS is treatment of choice in most cases with removal of incomplete BB by PPT. In case of complete BB PT appears more effective than NPT.

Incision rate of the Manas River, northern Tian Shan: Insight from luminescence dating of terrace cobbles

Fluvial deposits in piedmont environments are usually enriched by cobbles, which can be used for luminescence dating, as an alternative to the conventionally employed sand-sized minerals. In this study, a modified multi-elevated-temperature post-infrared infrared stimulated luminescence (MET-pIRIR) procedure was employed to establish luminescence-depth profiles of upper and lower sides of fluvial cobbles and obtain the burial ages of cobbles from high terrace of the Manas River in northern Chinese Tian Shan. The age-stimulation temperature (A-T) plateau was combined with the conventional age-depth (A-D) plateau in luminescence-depth profile to evaluate the reliability of burial ages of cobble luminescence dating from the aspects of fading and bleaching of signals. When the signal was only bleached to a limited depth given rise to no A-D plateau, the A-T plateau could serve as an internal-check to evaluate the degree of bleaching of the luminescence signal just through a single rock slice. Our results showed that self-evidenced and reliable buried ages of fluvial cobbles could be determined by only using first sub-surface rock slice in the presence of A-T plateau. Thereafter, the deposition age of cobble from top of T6 terrace and bottom of T5 terrace were ∼23.6–24.0 ka and ∼22.7 ka, respectively, inferring a very fast incision rate of ∼20 mm/a. The observed variability in bleaching depth between upper and lower sides across different cobble samples suggested complex transport dynamics.

New data on tributary terraces and a reappraisal of the incision history of the Jinshan Gorge, middle Yellow River

River channel profiles and river terraces are two typical landscape features to investigate river incision history. However, incision history inferred from the two markers can be inconsistent. For example, along the Jinshan Gorge in the middle Yellow River, pseudo-terraces (a virtual metric derived from channel profile modelling) suggest a recent acceleration in incision rates only in the southern gorge, and the northern keeps steady, while river terraces in the trunk channel indicate recently increased incision rates all along the gorge. To mitigate these discrepancies, we investigate six tributaries along the Jinshan Gorge by mapping and dating several strath terraces at various distances from the confluence to the trunk channel. By comparing tributary terraces of similar age, we find generally increasing incision rates towards the confluence with the trunk river in the southern Jinshan Gorge. North to south increasing incision rates along the gorge are also observed from coeval tributary terraces. In addition, two different landscapes between the southern and northern tributaries near the confluence are recognized, one with a deeply incised gorge and another one with floodplains, suggesting incision rate in the northern gorge is steady through time. Integrating the new infrared stimulated luminescence (IRSL) and Accelerator Mass Spectrometry (AMS) 14C data from tributaries with the abundant literature data of terrace samples mostly in the Jinshan Gorge dated with various methods, we suggest published ages from optically stimulated luminescence (OSL) might be too young. The methodological limitation associated to the dating method can explain the observed mismatch of incision history in the northern gorge inferred from pseudo-terraces and from river terraces in the trunk channel, and reconcile some contradicting patterns in published trunk terrace data.

Complications of Venous Thromboembolism Chemoprophylaxis in Lumbar Laminectomy With and Without Fusion.

The benefit of chemoprophylaxis (CPX) agents in preventing venous thromboembolism must be weighed against potential risks. Current literature regarding the efficacy of CPX after laminectomies with or without fusion is limited, with no clear consensus to inform guidelines. This study evaluated the association between CPX and surgical complications after lumbar laminectomy with and without fusion. Retrospective study of patients at a single large academic institution. The medical records of patients who underwent lumbar laminectomies with or without lumbar fusion from 2018 to 2020 were reviewed for demographics, surgical characteristics, CPX agents, postoperative complications, epidural hematomas, and wound drainage. Patients receiving CPX (n = 316) were compared with patients not receiving CPX (n = 316) via t test following propensity score matching, and patients on CPX were further stratified by fusion status. The CPX group had higher body mass index and American Society of Anesthesiologists grades. Rates of venous thromboembolism, epidural hematomas, infections, postoperative incision and drainage, transfusions, wound dehiscence, and reoperation were not associated with CPX. Moist dressings were more frequent, and average days of drain duration were longer with CPX. Overall postoperative complication rate and length of stay (LOS) were greater with CPX. The fusion subgroup had a lower Charlson Comorbidity Index, had a lower American Society of Anesthesiologists grade, was younger, had more women, and underwent more minimally invasive laminectomies. While estimated blood loss, operative times, and LOS were significantly greater in the fusion group, there was no difference in rate of intraoperative and postoperative complications. CPX after lumbar laminectomies with or without fusion was not associated with increased rates of epidural hematomas, wound complications, or reoperation. Patients receiving CPX had more postoperative cardiac complications, but it is possible that surgeons were more likely to prescribe CPX for higher-risk patients. They also had higher rates of ileus and moist dressings, greater LOS, and longer length of drain duration. Patients who underwent lumbar laminectomy with fusion on CPX tended to be lower risk yet incurred greater blood loss, operative times, LOS, cardiac complications, and hematomas/seromas than patients not undergoing fusion. This retrospective study compared surgical complications of lumbar laminectomies in patients who received chemoprophylaxis vs patients who did not. Chemoprophylaxis was not associated with increased rates of epidural hematomas, wound complications, or reoperation, but it was associated with higher rates of postoperative cardiac complications and ileus.

Slab Driven Quaternary Rock‐Uplift and Topographic Evolution in the Northern‐Central Apennines From Linear Inversion of the Drainage System

AbstractInvestigating rock‐uplift variations in time and space provides insights into the processes driving mountain‐belt evolution. The Apennine Mountains of Italy underwent substantial Quaternary rock uplift that shaped the present‐day topography. Here, we present linear river‐profile inversions for 28 catchments draining the eastern flank of the Northern‐Central Apennines to reconstruct rock‐uplift histories. We calibrated these results by estimating an erodibility coefficient (K) from incision rates and catchment‐averaged erosion rates obtained from cosmogenic‐nuclide data, and we tested whether a uniform or variable K produces a rock‐uplift model that satisfactorily fits independent geochronological constraints. We employ a landscape‐evolution model to demonstrate that our inversion results are reliable despite substantial seaward lengthening of the catchments during uplift. Our findings suggest that a rock‐uplift pulse started around 3.0–2.5 Ma, coinciding with the onset of extension in the Apennines, and migrated southward at a rate of ∼90 km/Myr. The highest reconstructed rock‐uplift rates (&gt;1 km/Myr) occur in the region encompassing the highest Apennine massifs. These results are consistent with numerical models and field evidence from other regions exhibiting rapid rock‐uplift pulses and uplift migration related to slab break‐off. Our results support the hypothesis of break‐off of the Adria slab under the central Apennines and its southward propagation during the Quaternary. Moreover, the results suggest a renewed increase in rock‐uplift rates after the Middle Pleistocene along the Adriatic coast, coeval with recent uplift acceleration along the eastern coast of southern Italy in the Apulian foreland.

Incision and rock uplift along the Lower Seine River since Marine Isotope Stage 8

ABSTRACTThe study of alluvial terraces helps in reconstructing the past geometries of rivers and makes it possible to assess the rate and pattern of fluvial incision and bedrock uplift. The fluctuations of river base levels are particularly variable and complex during the Late Quaternary in the lower course of rivers due to the interplay of responses to sea‐level fluctuations, tectonics and glacio‐isostasy. In this paper, the geometry and chronology of Manoir Brésil, an outcrop of alluvial terraces of the Lower Seine River, northern France, are investigated through a multidisciplinary study. Fluvial incision during MIS 8 in the Lower Seine in relation to sea‐level drop is recorded by an erosional surface cut into the chalk bedrock. This surface is covered by MIS 7 tidal deposits and then by younger, mostly periglacial colluvium (head). Manoir Brésil is therefore considered to be a chronological equivalent of the nearby, well‐studied Tourville‐la‐Rivière outcrop. The deposits are affected by post‐MIS 7 cryoturbation processes. Based on the local elevation of MIS 7 tidal deposits and erosional surfaces at Manoir Brésil, a minimum bedrock uplift rate of 25–40 m/Ma and an erosion rate of 125 m/Ma during glacial periods can be proposed. A regional correlation of the MIS 8 erosional surface is increasingly deformed by uplift towards the North, making it difficult to correlate the fluvial deposits along the Seine without precise chronological control. We interpret this regional tilt as the result of isostasy rebound after glaciations, consistent with the distribution of the elevations of MIS 5e and MIS 7 marine deposits along the English Channel.

An assessment of uncontrolled human interventions on the contemporary sediment budget and morphological alterations of the Vu Gia Thu Bon River basin, central Vietnam

The Vu Gia Thu Bon (VGTB) River basin is critical for regional development and prosperity in water resources. However, human interventions (e.g., dam construction and sand mining) have significantly affected this basin's sediment budget and morphological alterations over recent decades. Such humane actions drive an imbalance in water resources in the basin from upstream to downstream. Therefore, this study investigated spatiotemporal changes in sediment budget and morphology alterations using long-term data and bathymetric surveys; from these data, dams and sand mining contributions were quantified and differentiated. Based on field survey data and interviews, we estimated the sand-mining volume by incorporating reported and a newly proposed empirical formula. The results show that the total riverbed incision volume from 2010 to 2021 was 63.30 Mm3, with an incision rate of 0.14 m/yr. The officially reported sand-mining rate was 1.12 Mm3/yr, while the newly proposed empirical formula estimated 4.4 Mm3/yr. According to the developed empirical formula, the percentage reductions in the sediment budget due to sand mining and upstream dams were 69.7 % and 30.3 %, respectively, according to reports, and 17.8 % and 82.2 %. The statistical method was thus likely too conservative compared to the developed empirical formula. We found that the natural sediment supplies sourced from upstream were insufficient to compensate for the mined bed material. Therefore, our combination of different datasets permitted the assessment of future geomorphological developments within the VGTB River basin under the ongoing sediment deficits. The results of this study provide valuable insights into the impacts of human interventions, specifically sand mining, on the sediment budget, morphological alterations, and riverbed incision. The developed assessment forms the foundation for developing and expanding the region's water/sediment resource management strategies.

The how, when, and why of an abandoned bedrock meander of the Colorado River, Utah (U.S.)

AbstractRiver meanders entrenched into bedrock are found worldwide, and they are famously well represented in the Colorado Plateau of the southwestern U.S. Meandering of bedrock streams can eventually lead to cutting off canyon loops, and these abandoned “rincons” are locations with high preservation of fluvial deposits and landforms. We document and luminescence date the fluvial terraces in and around the Jackson Hole rincon along the Colorado River downstream of Moab, Utah. Results indicate cutoff and abandonment of the rincon at ~200 ka and also record the rapid and unsteady incision in this region over the past 300 ky. A convergence of conditions contributed to the cutoff of the rincon, including alluvial‐channel conditions at the onset of MIS 6 glacial‐climate, which provided channel‐bed cover and enhanced lateral erosion of weak strata. Also, a contemporaneous rock‐avalanche partially obstructed the paleochannel just downstream of the breach, potentially creating a backwater that further enabled a flood to avulse across the neck. Although other studies show that bedrock‐channel meandering and cutoff can generate unpaired strath terraces and short‐term increases in incision rates, these are not evident in the record at the Jackson Hole rincon. This novel case study leverages the high preservation potential within abandoned bedrock meanders to illuminate the processes and controls of rincon formation during landscape evolution.

Exploring heart dissection techniques for enhancing anatomical education: a pilot study to replicate transthoracic echocardiography.

For novice learners, converting two-dimensional (2D) images of echocardiography to three-dimensional (3D) cardiac structures is deemed challenging. This study aimed to develop an accurate dissection method of the heart to reproduce the transthoracic echocardiographic views on cadavers and elucidate new educational methods in human anatomy dissection courses. A total of 18 hearts were used in this study. After reflecting the anterior thoracic wall inferiorly, the hearts were excised from embalmed cadavers. Thereafter, three landmarks were set on the heart for each plane of the incision, and the hearts were incised to observe the three different echocardiographic views, which include the apical four-chamber view (A4C), parasternal long axis (PLAX) view, and parasternal short axis (PSAX) view at the papillary muscle level. If all structures for observation during routine echocardiography are clearly observed in each view, a successful incision is considered. All procedures and incisions were performed by the medical students. After a successful incision, hearts were returned to the original position in the pericardial sac for further observation. The success rates of incision for each view were 83.3% (5/6 success cases), 83.3% (5/6 success cases), and 66.7% (4/6 success cases) in the A4C view, PLAX view, and PSAX view at the papillary muscle level, respectively. This dissection method could probably be employed to reproduce transthoracic echocardiographic views on cadaveric hearts, which is beneficial for novice learners for a deeper understanding of the anatomy.

Cosmogenic nuclide-derived downcutting rates of canyons within large limestone plateaus of southern Massif Central (France) reveal a different regional speleogenesis of karst networks

Abstract. We present 35 new burial ages (27 sites) based on 26Al / 10Be ratios of terrestrial cosmogenic radionuclides measured in clasts and sediments deep within 12 caves in the southern Massif Central, France. Our results, together with previously published burial ages, verify that cave morphogenesis has been continuously active in this region for at least the past ∼ 6 Myr. Combining sample burial ages with their associated cave elevation above the modern stream bed gives a mean regional incision rate of 88 ± 5 m Ma−1 for the Grands Causses area. South of the Cevennes Fault Zone bordering the Grands Causses, the incision rate is 43 ± 5 m Ma−1, suggesting that this difference might be accommodated by the fault zone. Sediment burial ages from caves which are not located on river valley flanks or cliff walls are surprisingly too young compared to their expected ages when calculated using this regional average river incision rate. This suggests that the classical epigenic speleogenesis model that presumes a direct correlation between cave level development and regional base level lowering does not apply for the study area. Therefore, we propose that regional speleogenesis is mainly controlled by the removal of ghost rocks by headward erosion from river canyons to central parts of the plateaus, emptying incipient primokarst passages to create cave systems. Our results suggest a continuum process from hypogene primokarst composed of passages filled with ghost rock to one of epigene karst dynamics emptying these passages and creating cave networks. We propose that these processes are the major mechanism in the southern Massif Central that initiates speleogenesis and controls the geometry of the networks. In this region, tiered karst cannot be associated with the pace of incision of the major rivers but must be explained by former ghost rock (or hypogene) processes.

Comparative study of minimally invasive titanium elastic nail and steel plate on the treatment of fracture of tibiofibular fracture in adults

To compare the clinical outcomes of using elastic intramedullary nail and plate to fix fibular fracture. The 60 patients with tibiofibular fractures admitted from January 2015 to December 2022 were divided into two groups:intramedullary nail group and plate group, 30 cases each, intramedullary nail group was treated with elastic intramedullary nail fixation group, plate group was treated with steel plate and screw fixation group. Intramedullary nail group, there were 18 males and 12 females, aged from 22 to 75 years old with an average of (39.4±9.8) years old, including 24 cases of traffic accidents injury, 6 cases of falling injury, 23 cases of closed fractures, 7 cases of open fractures. Steel plate group, there were 15 males and 15 females, aged from 24 to 78 years old with an average of (38.6±10.2) years old. The 22 cases were injured by traffic accident, 8 cases were injured by falling. The 24 cases were closed fractures and 6 cases were open fractures. The operation time, intraoperative bleeding, American Orthopedic Foot and Ankle Society (AOFAS) ankle and hind foot scores, clinical healing time of fibula and the incidence of wound complications were compared between the two groups. The patients in both groups were followed up for 6 to 21 months, with an average of (14.0±2.8) months. Compared with plate group, intramedullary nail group had shorter operative time, less bleeding, shorter clinical healing time of fibula, and lower infection rate of incision, and the difference was statistically significant (P<0.05). There were 2 cases of delayed healing in intramedullary nail group, 1 case of nonunion in plate group, and 2 cases of delayed healing in plate group, and there was no statistically significant difference between the two groups (P>0.05). In the last follow-up, according to the AOFAS scoring standard, the ankle function in intramedullary nail group was excellent in 17 cases, good in 12 cases, fair in 1 case, with an average of (88.33±4.57) points, while in plate group, excellent in 16 cases, good in 10 cases, fair in 4 cases, with an average of (87.00±4.14) points;There was no statistical difference between the two groups (P>0.05). Elastic intramedullary nail has the advantages of short operation time, less intraoperative bleeding, short fracture healing time and less incision complications in the treatment of fibular fracture, which is worthy of clinical application.