Critical Threshold Research Articles

Soil microfauna mediate multifunctionality under multilevel warming in a primary forest

Abstract Soil microfauna play a crucial role in maintaining multiple functions associated with soil phosphorous, nitrogen and carbon cycling. Although both soil microfauna diversity and multifunctionality are strongly affected by climate warming, it remains unclear how their relationships respond to different levels of warming. We conducted a 3‐year multilevel warming experiment with five warming treatments in a subtropical primary forest. Using infrared heating systems, the soil surface temperature in plots was maintained at 0.8, 1.5, 3.0 and 4.2°C above ambient temperature (control). Our findings indicated that low‐level warming (+0.8–1.5°C) increased soil multifunctionality, as well as nematode and protist diversity, compared with the control. In contrast, high‐level warming (+4.2°C) significantly reduced these variables. We also identified significant positive correlations between soil multifunctionality and nematode and protist diversity in the 0–10 cm soil layer. Notably, we found that soil multifunctionality and protist diversity did not change significantly under 3.0°C warming treatment. Our results imply that a temperature increase of around 3°C may represent a critical threshold in subtropical forests, which is of great importance for identifying response measures to global warming from the perspective of microfauna in the surface soil. Our findings provide new evidence on how soil microfauna regulate multifunctionality under varying degrees of warming in primary forests.

EXPRESS: Impact of Unreliable Supplier on a Supply Chain with Demand-Generating Marketing

A firm often has multiple sourcing options for its product. Some suppliers may have longer lead times but offer lower prices, whereas reliable suppliers with quick response capabilities may have higher prices. Purchasing from a cheaper, less reliable supplier can help a firm lower its inventory cost but will expose itself to potential risks. This paper analyzes a supply chain in which a manufacturer can source from a cheaper, less reliable supplier with a long lead time and/or a reliable quick-response supplier. The manufacturer also has to make demand-generating marketing investments before the selling season. Our analysis shows that if the unreliable supplier’s reliability is low, the reliable supplier will charge a low wholesale price; otherwise, it will choose a high wholesale price. As the unreliable supplier’s reliability improves, the manufacturer is inclined to increase its marketing investment, but there is a drop at some critical threshold. Interestingly, the existence of an unreliable supplier can lead to a win-win outcome for the reliable supplier and the manufacturer. The unreliable supplier’s reliability has non-monotonic effects on the equilibrium profits of the reliable supplier and the manufacturer.

Epicardial Lead Performance Trends in Pediatric and Congenital Heart Disease.

Background: Epicardial pacing systems, rather than transvenous systems, are utilized in pediatric patients who are too small to undergo transvenous access and/or have complex congenital heart disease (CHD) anatomically precluding a transvenous system. Longitudinal performance studies indicate that epicardial leads have higher failure rates when compared with transvenous leads but there are limited data on lead measurement changes in the acute phase after implantation. The objective of this study was to assess epicardial lead performance in the acute postimplant period and at one-year follow-up. Methods: This is a retrospective single center study of children and adult patients with CHD undergoing epicardial bipolar pacing lead and generator implantation between January 2012 and June 2022. We empirically selected 2 V as a critical lead threshold. Results: There were 256 leads implanted in 127 patients (mean age 6.1 ± 9.8 years), including 201/256 (79%) leads in patients with CHD. At the time of implant, 47/256 leads (18%) had a lead threshold of ≥2 V. Of those, 42 of 47 (89%) had recorded threshold values on postoperative day 1 (POD1) and 37 of 42 (88%) had decreased to a more acceptable threshold that was <2 V. For patients with an implant threshold of ≥2 V; impedance >1000 ohms, presence of CHD, perioperative or acute postop status, and location of the lead (atrial vs ventricular) did not significantly impact the odds of having a persistently high threshold (≥2 V) on POD1. Conclusion: Epicardial pacing lead thresholds generally improve in the immediate postop period and in our experience most leads with a high implant threshold improved to <2 V by POD1.

Engineering exchange bias at the interface of self-polarized ultrathin ferroelectric BaTiO3 and ferromagnetic La0.67Sr0.33MnO3

We investigate the emergence and optimization of conventional exchange bias (EB) in ultrathin (&lt;10 nm) ferroelectric (FE) BaTiO3 (BTO)/ferromagnetic (FM) La0.67Sr0.33MnO3 (LSMO) epitaxial bilayers without an antiferromagnetic (AFM) material. The EB originates from the electronic orbital reconstruction at the FE-FM interface due to the ferroelectric polarization. We achieve maximum EB of approximately 42 Oe with single-domain polarization in nine-unit-cell-thick BTO, setting the BTO thickness above the critical threshold for ferroelectricity yet below the thickness of strain relaxation and multidomain breakdown. Furthermore, the LSMO layer needs to be thick enough to sustain both the FM layer and polarization-induced AFM spin configuration at the LSMO/BTO interface, yet as thin as possible to enable the EB loop shift. The temperature, training, field, and thickness dependence of the EB confirm that the LSMO/BTO interface exhibits conventional EB despite its unconventional origin. Using x-ray magnetic circular dichroism, scanning transmission electron microscopy, and density-functional-theory calculations, we confirm that the macroscopic EB effect originates from the interfacial AFM spin configuration in LSMO driven by FE-induced -orbital modifications in interfacial Mn ions. Thus, we engineer strong interfacial EB coupling in artificial multiferroics without a conventional AFM material by controlling FE polarization, highlighting the potential for advanced spintronic applications. Published by the American Physical Society 2024

Investigating the impact of tumor size on survival outcomes in thymoma and thymic carcinoma patients using the SEER database.

This study aims to clarify the impact of tumor size on the prognosis of patients diagnosed with thymoma and thymic carcinoma, leveraging data from a population-based registry. Utilizing the SEER database, this retrospective analysis identified patients diagnosed with thymoma and thymic carcinoma from 2000 to 2020. Propensity score matching was employed to mitigate potential statistical biases between groups categorized by tumor size (≤ 6.5cm and > 6.5cm). The study included a total of 3857 patients, comprising 2688 with thymoma and 1169 with thymic carcinoma. Multivariate analysis demonstrated that tumors ≤ 6.5cm independently correlated with improved Cancer-Specific Survival (CSS) (p = 0.001; p < 0.001) and Overall Survival (OS) (p < 0 .001; p < 0.001) in both thymoma and thymic carcinoma cohorts. Subgroup analysis revealed that smaller tumors (≤ 6.5cm) conferred survival benefits in patients with Masaoka-Koga stage IIB thymomas and stage III/IV thymic carcinomas (thymoma: CSS: p < 0.0001; OS: p = 0.00045; thymic carcinoma: CSS: p = 0.028; OS: p = 0.014). Additionally, WHO type A/AB/B1 and type B2/B3 thymomas with tumors ≤ 6.5cm exhibited superior CSS (p = 0.005; p < 0.00018) and OS (p = 0.015; p = 0.0021). Through propensity matching analysis utilizing the SEER database, this study underscores the prognostic significance of tumor size in both early-stage thymoma and advanced-stage thymic carcinoma, identifying a critical threshold of 6.5cm. In the WHO classification, tumor size based on the cut-off value of 6.5cm has a greater impact on the prognosis of type B2/B3 (high-risk group) than A/AB/B1 (low-risk group).

A statistical mechanics investigation of unfolded protein response across organisms.

Living systems rely on coordinated molecular interactions, especially those related to gene expression and protein activity. The Unfolded Protein Response is a crucial mechanism in eukaryotic cells, activated when unfolded proteins exceed a critical threshold. It maintains cell homeostasis by enhancing protein folding, initiating quality control, and activating degradation pathways when damage is irreversible. This response functions as a dynamic signaling network, with proteins as nodes and their interactions as edges. We analyze these protein-protein networks across different organisms to understand their intricate intra-cellular interactions and behaviors. In this work, analyzing twelve organisms, we assess how fundamental measures in network theory can individuate seed proteins and specific pathways across organisms. We employ network robustness to evaluate and compare the strength of the investigated protein-protein interaction networks, and the structural controllability of complex networks to find and compare the sets of driver nodes necessary to control the overall networks. We find that network measures are related to phylogenetics, and advanced network methods can identify main pathways of significance in the complete Unfolded Protein Response mechanism.

Effect of grain size gradient on the mechanical behavior of gradient nanograined pure iron: an atomic study

Abstract Using molecular dynamics (MD) simulation, the deformation mechanisms of gradient nanograined (GNG) pure iron (Fe) were investigated. Simulations of uniaxial tensile experiments were conducted on samples exhibiting different grain size gradients (GSGs). The simulation results reveal the presence of a critical GNG parameter (g), at which point the GNG-Fe attains its highest strength. The deformation mechanisms of three representative samples, namely GNG-2 with the g value at the threshold, GNG-1 with a g value smaller than the critical threshold and GNG-4 with a g value exceeding it, were thoroughly investigated. Within the coarse-grained (CG) region of GNG-1, the primary deformation mechanism is predominantly characterized by planar defects, rather than being dominated by dislocations. The mechanisms of both “strain hardening” and “softening” were observed and discussed in this region. The deformation of the coarse grains occurs in a coordinated manner, and the magnitude of the back-stress is insufficient to trigger grain boundary (GB) motion in the fine-grained (FG) region. In contrast, the deformation of the CG region in the GNG-4 primarily depends on dislocation. The “hardening” and “softening” effects of the dislocations were discussed. In the FG region of GNG-4, the grains undergo deformation primarily through GB motion, a phenomenon attributed to the significant back-stress generated by the uncoordinated deformation exhibited by the coarse grains. In the CG area of sample 2 with the g value at threshold, both dislocation- and planar defects-controlled mechanisms are observed. In the FG of this sample, neither GB migration and grain rotation are found. Only the GB width becomes larger, indicating that the back-stress transferred from the CG area makes the GB more active, but not large enough to induce the GB migration or grain rotation. The results of this work may provide some theoretical supports for the deformation mechanism of the GNG materials.

A computational algorithm for optimal design of a bioartificial organ scaffold architecture.

We develop a computational algorithm based on a diffuse interface approach to study the design of bioartificial organ scaffold architectures. These scaffolds, composed of poroelastic hydrogels housing transplanted cells, are linked to the patient's blood circulation via an anastomosis graft. Before entering the scaffold, the blood flow passes through a filter, and the resulting filtered blood plasma transports oxygen and nutrients to sustain the viability of transplanted cells over the long term. A key issue in maintaining cell viability is the design of ultrafiltrate channels within the hydrogel scaffold to facilitate advection-enhanced oxygen supply ensuring oxygen levels remain above a critical threshold to prevent hypoxia. In this manuscript, we develop a computational algorithm to analyze the plasma flow and oxygen concentration within hydrogels featuring various channel geometries. Our objective is to identify the optimal hydrogel channel architecture that sustains oxygen concentration throughout the scaffold above the critical hypoxic threshold. The computational algorithm we introduce here employs a diffuse interface approach to solve a multi-physics problem. The corresponding model couples the time-dependent Stokes equations, governing blood plasma flow through the channel network, with the time-dependent Biot equations, characterizing Darcy velocity, pressure, and displacement within the poroelastic hydrogel containing the transplanted cells. Subsequently, the calculated plasma velocity is utilized to determine oxygen concentration within the scaffold using a diffuse interface advection-reaction-diffusion model. Our investigation yields a scaffold architecture featuring a hexagonal network geometry that meets the desired oxygen concentration criteria. Unlike classical sharp interface approaches, the diffuse interface approach we employ is particularly adept at addressing problems with intricate interface geometries, such as those encountered in bioartificial organ scaffold design. This study is significant because recent developments in hydrogel fabrication make it now possible to control hydrogel rheology and utilize computational results to generate optimized scaffold architectures.

The Impact of Residential Building Insulation Standards on Indoor Thermal Environments and Heat-Related Illness Risks During Heatwaves: A Case Study in Korea

This study investigates the impact of building insulation standards on indoor thermal environments and the risk of heat-related illnesses during heatwaves in South Korea. Indoor temperatures were measured in residential buildings located in Chuncheon and Gwangju during the 2022 heatwave, with outdoor temperature data sourced from the Korea Meteorological Administration. Probability distribution fitting was used to estimate the likelihood of indoor temperatures exceeding the critical threshold of 27 °C. Additionally, a linear regression analysis was conducted to examine the relationship between the probability of exceeding the threshold and heat-related illness data from 2017 to 2023 provided by the Korea Disease Control and Prevention Agency. The findings reveal significant variations in indoor thermal conditions during heatwaves, influenced by factors such as building type, year of construction, and climate region, which affect the thermal insulation performance. Buildings with a lower thermal insulation performance were associated with higher indoor temperatures, increasing the likelihood of exceeding the critical threshold and contributing to a higher incidence of heat-related illnesses, particularly in provincial non-metropolitan areas. These results underscore the need for region-specific building insulation standards that address both winter energy efficiency and summer heatwave resilience. Enhancing thermal insulation in vulnerable regions could significantly reduce the risk of heat-related illnesses and improve public health resilience to extreme heat events.

Effects of Moisture Content and Heat Treatment on the Viscoelasticity and Gelation of Polyacrylonitrile/Dimethylsulfoxide Solutions

Polyacrylonitrile (PAN) gels create significant obstacles in industrial fiber spinning by forming insoluble networks that compromise solution stability and uniformity. This study investigates the rheological properties of PAN/dimethyl sulfoxide (DMSO) solutions, examining how aging time, moisture content, and polymer concentration affect gelation behavior. Dynamic rheological analysis revealed that both physical and chemical crosslinks play crucial roles in gel formation, with gelation accelerating markedly when moisture content exceeds 3% and aging progresses. Under heat treatment at 80 °C, samples with increased moisture content demonstrated rapid transitions to solid-like states, indicating a critical moisture threshold for enhanced gelation kinetics. Additionally, reductions in polymer concentration disrupted physical crosslink density, thereby mitigating gel formation. These results underscore the importance of precisely controlling moisture and concentration parameters in PAN solutions to stabilize solution properties and minimize gel formation, thus enhancing process efficiency and quality in PAN-based carbon fiber production.

Impact of Land Use and Land Cover Changes on Soil Physico-Chemical Properties in Southern Tigray, Northern Ethiopia

Soil quality declines due to the conversion of natural vegetation into farmland and grazing areas. The response of soil properties to land use and land cover changes (LULC) exhibits both spatial and temporal variations. This study aimed to assess the effects of LULC changes on the physico-chemical properties of soil in the Wojic watershed. Soil samples were collected from natural forests, bushland, shrubland, and cultivated lands across three landforms of the watershed (upper, middle, and lower) to evaluate the physical and chemical properties of the soil associated with different LULC types. The LULC categories were compared using mean values and critical thresholds for selected physicochemical soil properties. Soil analysis was conducted using R software, employing one-way analysis of variance (ANOVA). A normality test was performed before the post hoc analysis, and Tukey’s honest significance difference (HSD) test was utilized for mean separation among the LULC types. Additionally, a normalized difference vegetation index (NDVI) was calculated for the years 1997 and 2017. A simple linear regression model was developed to estimate soil physico-chemical properties over the past 20 years, using laboratory soil parameters and the NDVI for 2017. The pH values showed a slight decrease in cultivated land (from 5.7 to 5.4), bushland (from 7 to 6.6), and shrubland (from 6.5 to 6.2) over the study period. The analysis indicated a declining trend in physico-chemical properties, attributed to changes in vegetation cover and management practices. Consequently, the government needs to enforce policies and regulations that promote effective land resource management and utilization, with particular emphasis on the proper management and conservation of forests, bushlands, and shrublands, as well as measures to prevent increased land resettlement.

Sensibility in the impact of aeolian sand cover on permafrost degradation in Qinghai-Xizang Plateau

Abstract Environmental transformations and intensifying desertification across the Qinghai-Xizang Plateau significantly influence permafrost degradation, heightening risks associated with carbon emissions, thermal hazards, and infrastructural damage. However, the specific response of permafrost to desertification remains insufficiently understood. Here, we employed numerical modelling to examine the sensitivity of the impact of aeolian sand cover (ASC) on permafrost degradation. Our findings reveal that the thickness and moisture content of ASC profoundly affects permafrost degradation. Moreover, permafrost thermal stability and the rate of climatic warming modulate this degradation process. The simulation results identify two critical thickness thresholds for ASC: 20 cm and 80-120 cm. Specifically, dry ASC thinner than 20 cm accelerates permafrost degradation driven by desertification, whereas ASC thicker than 20 cm mitigates this effect. Furthermore, increased moisture in ASC extends the thickness thresholds to 80-120 cm. These results suggest that climatic variations in the Qinghai-Xizang Plateau, particularly transitions towards either warming-drying or warming-wetting, will markedly influence the response of permafrost to desertification. Notably, a warming-drying climate may reduce the potential degradation of permafrost caused by desertification. This study provides a critical reference for understanding the impact of aeolian desertification on permafrost in regions beyond the Qinghai-Xizang Plateau. It holds significant policy implications for environmental conservation and infrastructure development within the plateau.

Perspectives on Ergodic Cancer Therapy Derived from Cloning Genome Chaos via In Vivo Rhabdomyosarcoma RA-2 Models: a Narrative Review.

This review explores articles concerning the experimental research cycle on genome instability in cell populations of highly malignant recurrent organotropic rhabdomyosarcoma RA- 2 in rats. Clonal analysis and cloning were pivotal components of this research, which relies on the frequency of cells with micronuclei and internuclear bridges to gauge the intensity of chromothripsis and break-fusion-bridge cycles. The efficacy of cloning, determined by these indicators, stemmed from the deliberate isolation of tumor stem cells, yielding clones in which chromothripsis activity and breakage-fusion-bridge cycles were sustained. Notably, it is plausible that the stem cells themselves, progenitors of these clones, harbor dicentric chromosomes and chromosomal fragments, contributing to the formation of "fatal micronuclei" in their karyotype. Cloning based on bridges and micronuclei has proven effective up to a certain threshold (15%-18%), reaffirming the predicted reproductive extinction of malignant cell populations under mutational pressure and genome chaos, as posited by the genetic theory of cell populations. Furthermore, this review highlights the potential of ergodic cancer therapy as a novel therapeutic strategy. Ergodic therapy offers promising prospects for late-stage and terminal malignant tumors, where conventional treatments may fall short due to advanced progression. Furthermore, by "enhancing chromothripsis" through the induction of additional micronuclei and bridges, ergodic cancer therapy seeks to increase genome chaos to a critical threshold, potentially halting malignant progression. This innovative approach presents opportunities to explore new drugs and targets for chromothripsis-based oncotherapy, addressing the pressing need for effective treatments in advanced stages of malignancy.

Sequestration of gene products by decoys enhances precision in the timing of intracellular events

Expressed gene products often interact ubiquitously with binding sites at nucleic acids and macromolecular complexes, known as decoys. The binding of transcription factors (TFs) to decoys can be crucial in controlling the stochastic dynamics of gene expression. Here, we explore the impact of decoys on the timing of intracellular events, as captured by the time taken for the levels of a given TF to reach a critical threshold level, known as the first passage time (FPT). Although nonlinearity introduced by binding makes exact mathematical analysis challenging, employing suitable approximations and reformulating FPT in terms of an alternative variable, we analytically assess the impact of decoys. The stability of the decoy-bound TFs against degradation impacts FPT statistics crucially. Decoys reduce noise in FPT, and stable decoy-bound TFs offer greater timing precision with less expression cost than their unstable counterparts. Interestingly, when both bound and free TFs decay at the same rate, decoy binding does not directly alter FPT noise. We verify these results by performing exact stochastic simulations. These results have important implications for the precise temporal scheduling of events involved in the functioning of biomolecular clocks, development processes, cell-cycle control, and cell-size homeostasis.

Releasing long bubbles trapped in thin capillaries via tube centrifugation and inclination

In confined systems, the entrapment of a gas volume with an equivalent spherical diameter greater than the dimension of the channel can form extended bubbles that obstruct fluid circuits and compromise performance. Notably, in sealed vertical tubes, buoyant long bubbles cannot rise if the inner tube radius is below a critical value near the capillary length. This critical threshold for steady ascent is determined by geometric constraints related to the matching of the upper cap shape with the lubricating film surrounding the elongated part of the bubble. Developing strategies to overcome this threshold and release stuck bubbles is essential for applications involving narrow liquid channels. Effective strategies involve modifying the matching conditions with an external force field to facilitate bubble ascent. However, it is unclear how changes in acceleration conditions affect the motion onset of buoyancy-driven long bubbles. This study investigates the mobility of elongated bubbles in sealed tubes with an inner radius near the critical value inhibiting bubble motion in a vertical setting. Two strategies are explored to tune bubble motion, leveraging variations in axial and transversal accelerations: tube rotation around its axis and tube inclination relative to gravity. By revising the geometrical constraints of the simple vertical setting, the study predicts new thresholds based on rotational speed and tilt angle, respectively, providing forecasts for the bubble rising velocity under modified apparent gravity. Experimental measurements of motion threshold and rising velocity compare well with theoretical developments, thus suggesting practical approaches to control and tune bubble motion in confined environments.

Relationship between lactate levels and 28-day mortality in pediatric sepsis: results from the pediatric intensive care database

ObjectiveThis study aimed to investigate the relationship between serum lactate levels at admission to the intensive care unit (ICU) and the clinical outcomes of children with sepsis.MethodsWe used the Pediatric Intensive Care (PIC) database to identify 288 pediatric patients with sepsis. We analyzed the relationship between lactate levels and hospital and ICU mortality in sepsis by establishing a segmented multivariable Cox regression model. We also conducted subgroup analysis as well as analyzed the restricted cubic spline curves.ResultsAfter adjusting for all potential confounding factors, an increase of 1 mmol/L in lactate levels was found to be associated with an 17% rise in the 28-day hospital mortality risk among sepsis patients (HR: 1.17, 95% CI: 1.08–1.27, P = 0.0002). When considering lactate as a categorical variable, the mortality risk of patients with lactate levels ≥ 2.2 mmol/L was significantly increased (HR: 3.61, 95% CI: 1.24–10.54, P = 0.0189). The restricted cubic spline curve analysis revealed a nonlinear correlation between lactate and 28-day mortality, with an inflection point at 2.2 mmol/L. Similar findings were also observed in the assessment of secondary outcomes.ConclusionsOur study demonstrates a non-linear correlation between lactate levels and 28-day mortality in pediatric sepsis, with a critical threshold of 2.2mmol/l for lactate levels in septic patients. Early assessment of lactate levels is recommended for children with sepsis to facilitate prompt intervention and mitigate the risk of fatality.

Opportunities for Earth Observation to Inform Risk Management for Ocean Tipping Points

AbstractAs climate change continues, the likelihood of passing critical thresholds or tipping points increases. Hence, there is a need to advance the science for detecting such thresholds. In this paper, we assess the needs and opportunities for Earth Observation (EO, here understood to refer to satellite observations) to inform society in responding to the risks associated with ten potential large-scale ocean tipping elements: Atlantic Meridional Overturning Circulation; Atlantic Subpolar Gyre; Beaufort Gyre; Arctic halocline; Kuroshio Large Meander; deoxygenation; phytoplankton; zooplankton; higher level ecosystems (including fisheries); and marine biodiversity. We review current scientific understanding and identify specific EO and related modelling needs for each of these tipping elements. We draw out some generic points that apply across several of the elements. These common points include the importance of maintaining long-term, consistent time series; the need to combine EO data consistently with in situ data types (including subsurface), for example through data assimilation; and the need to reduce or work with current mismatches in resolution (in both directions) between climate models and EO datasets. Our analysis shows that developing EO, modelling and prediction systems together, with understanding of the strengths and limitations of each, provides many promising paths towards monitoring and early warning systems for tipping, and towards the development of the next generation of climate models.

Metal Resistance of Microorganisms as a Crucial Factor for Their Homeostasis and Sustainable Environment

Heavy metals are prevalent environmental components, but when their concentrations exceed critical thresholds, they pose environmental hazards, disrupting the sustainability of ecosystems. Microorganisms are among the first to encounter the toxic effects of metals. Therefore, it is crucial to understand both the levels and mechanisms of their resistance to maintain their homeostasis under the pressure of extreme factors as well as contribute to increasing the sustainability of ecosystems. The aim of the study was to examine two soil bacterial strains, Brevundimonas vesicularis USM1 and Pseudomonas putida USM4, to assess their resistance levels to toxic metals and to identify the mechanisms behind this resistance. For this purpose, microbiological, statistical, and bioinformatics methods were used. The comparative analysis of the two strains revealed that P. putida USM4 exhibited greater resistance to Cr(VI), Co(II), Cu(II), Ni(II), and Fe(III) compared to B. vesicularis USM1. This was confirmed by the metal concentrations at which the strains could survive, their growth dynamics, and the genetically based resistance mechanisms. These findings enhance our understanding of microbial metal resistance and contribute to the advancement of microbial-based environmental biotechnologies.

Environmental critical thresholds based on statistical analysis for modelling landslide susceptibility in Continental Basaltic Provinces

Abstract. The study aims to estimate the environmental critical thresholds using statistical approaches to understand the landslide conditioning factors that can trigger landslides in the Continental Basaltic Provinces a landslide-prone area, using as reference the landslides that occurred in an extreme rainfall event. The study area is a region that was the scene of an extreme hydrological event in January 2017, with an accumulated volume of rain of 163.9 mm in 8 hours, causing a widespread event of shallow planar landslides with more than 400 scars detected. Hydrological, anthropic, geological, geomorphological, and topographical features of this region were analyzed considering landslides and non-landslides samples set, and their influence in the event was carried out using the Frequency Ratio method, followed by Pearson's Linear Correlation Coefficient and Linear Regression. The results showed that this process helped us to understand environmental critical thresholds based on classes of conditioning factors that have a greater influence on rainfall-triggered landslide occurrences and, consequently, higher predictive capacity in the landslide susceptibility models with the same geoenvironmental parameters which is a valuable insight for risk management.

Numerical investigation of the refractive properties of near-horizontal rocky shore platforms and their effects on harmonic and stationary wave patterns

Near-horizontal shore platforms display highly irregular plan shapes, but little is known about the way in which these irregularities influence the significant wave height (Hŝ) on the platforms and the frequency components of the nearshore wavefield. As ocean waves share akin refractive properties to light rays, it can be assumed that, similarly to optical lenses, shore platforms can separate waves according to their frequency depending on their geometry. Thus, we use a non-linear Boussinesq wave model to conduct harmonic and bispectral mode decomposition analyses to study the control of concave and convex platform edges over wind waves (WW: 0.125–0.33 Hz), swell waves (SW: 0.05–0.125 Hz) and infragravity (IG: 0.008–0.05 Hz) waves frequencies. For breaking and non-breaking waves, increasing the platform edge concavity intensified wave divergence and subsequent attenuation of SW and IG across the outer platforms, reducing Hŝ by up to 25 %. Increasing the platform edge convexity intensified focusing and amplification of SW and WW over the outer platforms, increasing Hŝ by up to 18 % and 55 % for breaking and non-breaking waves. In the presence of breaking, IG amplification was affected by wave divergence across the inner platform, a condition determined by a critical convex curvature threshold (K=1.8) balancing wave focusing from refraction and defocusing from breaking. We find that convex curvature can determine the relative dominance of WW, SW and IG across platforms. Alongshore, coherent wave interactions governed IG stationary patterns defined by a node near the platform centreline and two antinodes on either side of concave edges. A node was generated at the platform centreline, and two antinodes were observed on either side of the convex edges for K>1.8, with the opposite pattern observed for K<1.8. Such patterns likely result in alongshore variations in wave-generated currents and erosion shaping rock coasts.