Transition Interval Research Articles

Transitions in metabolic syndrome and metabolic obesity status over time and risk of urologic cancer: A prospective cohort study.

The effects of metabolic obesity (MO) phenotypes status and their dynamic changes on urologic cancer (UC) is ignored. We aimed to investigate the association between metabolic syndrome (MetS) and MO status at baseline, their dynamic changes and UC risk. This paper studied 97,897 subjects who were free of cancers at baseline (2006-2007). Individuals were classified into four MO phenotypes by MetS and obesity at baseline. Transitions in MetS and MO status from 2006-2007 to 2008-2009 were considered. The hazard ratios (HRs) and 95% confidence intervals (CIs) for UC were assessed by multifactorial Cox proportional risk regression models. The main limitations of this study are as follows: the ratio of men to women in the cohort is unbalanced; the impacts of MetS and MO on each cancer type (kidney cancer, prostate cancer, bladder cancer) have not been analyzed separately; the transition intervals of MetS and MO phenotypes are relatively short. From baseline (2006-2007) survey to December 31, 2020, during a median follow-up of 14.02 years, 554 cases of UC were diagnosed. Participants with MetS [HRs (95% CI) = 1.26 (1.06-1.49)] and metabolically unhealthy obesity (MUO) [HRs (95% CI) = 1.49 (1.17-1.89)] had significantly higher risk of UC than those with non-MetS and metabolically healthy normal weight (MHN). Transitions in MetS and MO phenotypes over time were studied. Compared with non-MetS to non-MetS, the risks for UC in MetS to MetS [HRs (95% CI) = 1.45 (1.11-1.88)] was increased. Compared with MHN to MHN, both MUO to metabolically healthy obesity (MHO) [HRs (95% CI) = 2.65 (1.43-4.92)] and MUO to MUO [HRs (95% CI) = 1.60 (1.06-2.42)] had significantly higher UC risk. MetS and MUO increased the UC risk at baseline. Transitions of MetS to MetS, MUO to MUO and even MUO to MHO over time significantly increased the risk of UC development.

Multiple controls on the preservation of organic matter in the lower Mississippian Luzhai Formation black shale in southern China

The early Carboniferous experienced profound climate cooling that drove the Earth's climate from a mid-Paleozoic greenhouse into the Late Paleozoic Ice Age. Several climate cooling events have been reported, including the Tournaisian and Visean (early to mid-Early Carboniferous). In this study, we perform multi-proxy analyses (organic carbon isotopes, nitrogen isotopes, major and trace elements and organic petrology/geochemistry) of samples from an early Carboniferous section in Nandan region (Guangxi, China). Our goal is to investigate the global carbon‑nitrogen cycle, and associated oceanic productivity and redox perturbations, during a key climatic transition interval, as well as the controls on organic matter enrichment in the sediments. The carbon and nitrogen isotope profiles of the Nandan section record major perturbations during the mid-Tournaisian and early Visean. The mid-Tournaisian carbon isotope excursion (TICE) is marked by a positive δ13Corg shift of 1.8 ‰ (from −27.7 ‰ to −25.9 ‰), correlating with a positive δ15N shift. The early Visean carbon isotope excursion (VICE) is characterized by a positive shift in δ13Corg (from −28.2 to −25.5 ‰, with an excursion magnitude of 2.7 ‰), but associated with a negative shift in δ15N (from +5 ‰ to +4 ‰). The positive δ13Corg excursions during these events most likely reflect enhanced organic matter burial with expansion of anoxic seafloor in the global ocean. The drop in nitrogen isotope values in the early Visean is interpreted to be linked with less denitrification under more oxic conditions. The decrease of organic matter contents up section is consistent with the shift to more oxic conditions and increased sedimentary dilution caused by sea-level fall, which is ultimately controlled by orogenic events and climate cooling.

The rheology of rhyolite magma from the IDDP-1 borehole and Hrafntinnuhryggur (Krafla, Iceland) with implications for geothermal drilling

Changes in rhyolite melt viscosity during magma decompression and degassing exert a first order control on ascent through the crust and volcanic eruption style. These changes have as yet unknown hazard implications for geothermal drilling in pursuit of particularly hot fluids close to magma storage regions. Here, we exploit the situation at Krafla volcano in which rhyolite has both erupted at Earth's surface and been sampled at shallow storage depths via drilling of the 2009 IDDP-1 and 2008 KJ-39 boreholes. We use differential scanning calorimetry to constrain that the IDDP-1 magma quenched to glass at ∼ 700 K, at a rate of between 7 and 80 K.min−1. We measure the equilibrium viscosity of the IDDP-1 rhyolite at temperatures close to the glass transition interval and show that the rhyolite viscosity is consistent with generalized viscosity models assuming a dissolved H2O concentration of 2.12 wt%. We couple these results with micro-penetration and concentric cylinder rheometry over a range of potential magma storage temperatures to constrain the response of surficial Krafla rhyolites to stress. The surficial rhyolites at Krafla match the same viscosity model, assuming a lower dissolved H2O concentration of 0.12 wt%. Our results show that at a storage temperature of 1123–1193 K, the viscosity of the stored magma is ∼ 3×105 Pa.s. At the same temperature, the viscosity following degassing during ascent to the surface rises to ∼ 2×109 Pa.s. Finally, we use high-stress compression tests on the Hrafntinnuhryggur surface obsidian to determine the onset of unrelaxed behavior and viscoelastic melt rupture or fragmentation pertinent to understanding the melt response to rapid pressure changes that may be associated with further (near-) magma exploration at Krafla. Taken together, we characterize the relaxation and viscosity of these magmas from source-to-surface.

Effect of annulus ratio on the residence time distribution and Péclet number in micro/milli‐scale reactors

AbstractMicro/milli‐scale annular reactor with straight and helical forms has excellent heat and mass transfer performance due to the short molecular diffusion distance and dual‐wall surface transport. The annular gap spacing is scalable by adjusting the inner and outer tube diameter. The influence of diffusion and convection effects on axial dispersion as expanding the flow scale requires further elucidation with the help of residence time distribution (RTD) curves and Péclet (Pe) numbers. The correlation of RTD characteristics with annulus ratio γ = Dh/D (ratio of annulus characteristic size to outer diameter) is investigated using computational fluid dynamics. Results show that with enlarging the straight annular gap from micro‐scale to milli‐scale, RTD characteristics exhibit opposing patterns. This can be attributed to the transition from diffusion‐dominated to convection‐dominated on momentum transfer, and the transition interval is 0.167 < γ < 0.250. Correlation equations of Pe number with Reynolds (Re) number and γ are established under diffusion‐dominated and convection‐dominated states. The symmetrically distributed secondary flow in the helical annular gap effectively elevates the Pe (Pemax > 100). Correlation equations of Pe with Re and γ are established in helical annular gaps with 0.083 < γ < 0.208 and 0.167 < γ < 0.500. The above results contribute to understanding the annular flow RTD characteristics for better applications of tube‐in‐tube reactors.

Comparison of Day-Specific Serum LH, Estradiol, and Progesterone with MiraTM Monitor Urinary LH, Estrone-3-glucuronide, and Pregnanediol-3-glucuronide Levels in Ovulatory Cycles.

Background and Objectives: Fertility tracking apps and devices are now currently available, but urinary hormone levels lack accuracy and sensitivity in timing the start of the 6-day fertile window and the precise 24 h interval of transition from ovulation to the luteal phase. We hypothesized the serum hormones estradiol (E2) and progesterone (P) might be better biomarkers for these major ovulatory cycle events, using appropriate mathematical tools. Materials and Methods: Four women provided daily blood samples for serum E2, P, and LH (luteinizing hormone) levels throughout their entire ovulatory cycles, which were indexed to the first day of dominant follicle (DF) collapse (defined as Day 0) determined by transvaginal sonography; therefore, ovulation occurred in the 24 h interval of Day -1 (last day of maximum diameter DF) to Day 0. For comparison, a MiraTM fertility monitor was used to measure daily morning urinary LH (ULH), estrone-3-glucuronide (E3G), and pregnanediol-3-glucuronide (PDG) levels in three of these cycles. Results: There were more fluctuations in the MiraTM hormone levels compared to the serum levels. Previously described methods, the Fertility Indicator Equation (FIE) and Area Under the Curve (AUC) algorithm, were tested for identifying the start of the fertile window and the ovulation/luteal transition point using the day-specific hormone levels. The FIE with E2 levels predicted the start of the 6-day fertile window on Day -7 (two cycles) and Day -5 (two cycles), whereas no identifying signal was found with E3G. However, both pairs of (E2, P) and (E3G, PDG) levels with the AUC algorithm signaled the Day -1 to Day 0 ovulation/luteal transition interval in all cycles. Conclusions: serum E2 and (E2, P) were better biomarkers for signaling the start of the 6-day fertile window, but both MiraTM and serum hormone levels were successful in timing the [Day -1, Day 0] ovulatory/luteal transition interval. These results can presently be applied to urinary hormone monitors for fertility tracking and have implications for the direction of future fertility tracking technology.

Computational Investigation of the Influencing Parameters on the Solidification of Thermoplastic Beryllium Oxide Slurry in a Cylindrical Shell

This article presents a computational study of the influencing parameters on the solidification of the thermoplastic beryllium oxide slurry in an annular forming cavity. The main purpose of this paper is to study the effect of cooling and casting conditions on the solidification of the BeO suspension by considering the temperature-dependent rheological and physical properties. The results of calculations of the Bingham–Papanastasiou rheological model with experimental data in the intervals of phase transitions with different casting rates of beryllium ceramics have been validated. The use of the regularization parameter made it possible to approximate the flow of the slurry at all levels of its shear rates as highly viscous, followed by a continuous transition to a solid state. The speed of heat removal from the molding during the solidification period is determined by the speed of movement of the slurry and the temperature field on which the width of the transition region depends. The process of solidification of the slurry mass has been evaluated by changing its heat flow distribution and density along the length of the concentric channel. The obtained model calculation results make it possible to control the casting process and eventually realize a uniform structure of castings.

Oceanography of the Eastern Equatorial Pacific Ocean Across the Oligocene‐Miocene Transition

AbstractThe functioning of the Pacific Ocean—the world's largest ocean—during a warmer‐than‐present paleoclimate state remains underexplored. We present planktonic and benthic foraminiferal stable oxygen (δ18O) and carbon (δ13C) isotope records from Integrated Ocean Drilling Program (IODP) Site U1334 that span the Oligocene‐Miocene Transition (OMT) interval, from 24.15 to 21.95 million years ago (Ma). We reconstruct (sub‐)surface and deep‐water conditions and provide better constraints on the physical and chemical oceanography of the eastern equatorial Pacific Ocean (EEP). Positive trends in planktonic and benthic foraminiferal δ18O values, mark a largely uniform imprint of increased land‐ice volume/global cooling on surface‐ and deep‐waters. We document a delayed planktonic foraminiferal δ18O increase across the OMT as well as an increase in the amplitude variability of planktonic foraminiferal δ18O values on eccentricity timescales during the early Miocene. We interpret this as an enhanced glacioeustatic sea‐level control on Atlantic‐Pacific salinity exchange through the Central American Seaway (CAS) or as the onset of more variable surface currents and oceanic fronts in the EEP. Positive trends in planktonic and benthic foraminiferal δ13C values characterize the whole‐ocean depletion in 12C linked to organic carbon burial during the Oligocene‐Miocene carbon maximum (CM‐OM). However, this depletion is more pronounced in the planktonic foraminiferal δ13C record, especially during ∼400 Kyr eccentricity minima, reflecting an increase in nutrient upwelling and the efficacy of the biological carbon pump (BCP) when global temperatures decreased across the OMT and during the early Miocene. Our study highlights the dynamic behavior of the EEP in a warmer‐than‐present unipolar icehouse state.

Nontrivial effects of geometric and charge defects on one-dimensional confined water

Water confined within nanochannels with specific functionalities serves as the foundation for a variety of emerging nanofluidic applications. However, the structure and dynamics of the confined liquid are susceptibly influenced by practically hard-to-avoid defects, yet knowledge of this fact remains largely unexplored. Here, using extensive molecular dynamics simulations, we elucidate the significant influence of geometric and charge defects on one-dimensional confined water. We show that the two types of defects can both reshape the water density distribution by constraining the translocation of water molecules along the circumferential direction. In addition to structural alterations, collective translocation and rotation of water slabs arise during transportation under external pressure. Below the temperature threshold marking the initiation of liquid-solid transition, the geometric defect retards water diffusion through a pinning effect, while the charge defect induces an anti-freezing effect. The latter is attributed to the electrostatic interaction between the charge defect and water molecules that hinders the formation of a stable hydrogen bond network by disrupting molecular dipole orientation. Consequently, this behavior results in a reduction in the number and lifetime of hydrogen bonds within the phase transition interval. The distinct roles of the two types of defects could be utilized to control the structure and dynamics of confined liquids that may result in distinct functionalities for nanofluidic applications.

Experimental study on immiscible and miscible dynamic characteristics of CO2 and crude oil in visual slim tube

CO2 flooding for oil recovery is a dynamic process that requires further investigation of oil-gas interface change characteristics, interfacial mass transfer processes, and oil-gas composition variation during both immiscible and miscible displacement. Understanding these factors is crucial for better comprehending their impact on CO2-enhanced oil recovery (EOR). This research used a jointly developed CO2 miscible visual flooding experimental apparatus to study the horizontal dynamic characteristics of CO2 and crude oil under different pressures and flow rates in visual slim tube. At 10 MPa, the stratification results of CO2 and crude oil indicate that the experiment is immiscible flooding. The contact angle (7.9°) between the two phases of CO2 and crude oil at the flow rate of 15 cm/min is larger than that (5.2°) at 1.5 cm/min, and the grey scale of CO2 increases at 100 cm/min. The quantity, individual content, and shape of the light and medium hydrocarbon components condensed on the inner wall of the tube vary with different flow rates. At 15 MPa, the appearance of the CO2 and crude oil transition interval proves that the experiment is miscible flooding. At different flow rates, the inclination angle and distribution of black stripes vary. The whole transition interval is divided into 6 intervals, and the transition interval lengthens with increasing fluid velocity. The experiments visually demonstrate the occurrence of the miscible phase, and identify experimental pressure and fluid flow rate as key factors influencing the miscibility of CO2 and crude oil.

Термічне розширення аморфних халькогенідних матеріалів в околі температури склування

The patterns of thermal expansion of chalcogenide materials in the temperature range from room temperature to the beginning of deformation of the samples under the action of the measured force of the dilatometer cell were investigated. Above the glass transition temperature, the coefficient of linear thermal expansion of stabilized samples increases dramatically. For tempered glasses, the course of the temperature dependences of the relative elongation of the samples significantly depends on their thermal history and is of a complex nature. According to dilatometric measurements, the characteristic temperatures of the glass transition interval were determined, a qualitative assessment of structural changes was made depending on the temperature-time regimes of synthesis and annealing of chalcogenide glasses.

Differential Scanning Calorimetry of Proteins and the Two-State Model: Comparison of Two Formulas

Differential Scanning Calorimetry (DSC) is a regular and powerful tool to measure the specific heat profile of various materials. In order to connect the measured profile to the properties of a particular protein, a model is required to fit. We discuss here the application of an exact two-state formula with its approximation and process the DSC experimental data on protein folding in water. The approximate formula relies on the smallness of the transition interval, which is different for each protein. With an example of the set of 33 different proteins, we show the practical validity of the approximation and the equivalence of exact and approximate two-state formulas for processing DSC data.

Sedimentology and ichnology of the Xiaxishancun Formation of Qujing, Yunnan: Earliest Devonian marginal-marine environments and ecosystems in South China

The Silurian–Devonian transition experienced dramatic changes of climates, global carbon cycles and faunas, but detailed documentation of the environments and biotas during this transitional interval in the South China Block is needed. The upper Silurian–Lower Devonian sequence of Qujing, Yunnan, southwestern China, represents one of the rare stratigraphic records of this transition in the South China Block. In this study, the Xiaxishancun Formation of Qujing, a unit generally considered earliest Devonian in age, is studied in terms of sedimentology and ichnology. The results show that the Xiaxishancun Formation typically records the deposition of hyperpycnal flow systems, which have been rarely reported in the Paleozoic. Three facies associations, including mudstone-dominated association, heterolithic association, and sandstone-dominated association, represent different parts of the channels and lobes of hyperpycnal subaqueous deltas on the shelf. Nineteen ichnogenera and 32 ichnospecies were distinguished in the Xiaxishancun Formation, and grouped into two ichnoassemblages, the Lockeia-Ptychoplasma-Oravaichnium ichnoassemblage in hummocky/swaley cross-stratified sandstones, and the Cruziana-Diplichnites-Monomorphichnus ichnoassemblage in thin rippled sandstone beds. The hyperpycnal depositional processes of the Xiaxishancun Formation created nutrient-rich, oxygen-rich, siliciclastic environments that supported diverse benthic ecosystems. Our study provides new insights into the understanding of marginal-marine environments and biotas of South China, immediately following the Silurian–Devonian transition event.

Trends in estuarine pyrite formation point to an alternative model for Paleozoic pyrite burial

The early Paleozoic Era (∼540–420 Ma) was an interval of profound biogeochemical changes including increasing oxygen (O2) and the onset of bioturbation (sediment mixing by animals). It is hypothesized that incipient bioturbation caused a monotonic decrease in sedimentary burial of pyrite (FeS2), which would have slowed atmospheric O2 accumulation. However, pyrite accumulation can exhibit complex responses to dynamic, low-O2 environmental conditions. To assess pyrite burial in a potential modern analogue to early Paleozoic environments, we collected sediment cores from the Chesapeake Bay, an estuary with multiple gradients in sulfate concentration, hypoxia intensity, organic carbon flux and lability, and bioturbation. Results indicate that pyrite accumulation is maximized not under strong sulfate depletion in highly reducing sediments, but rather in sediments that occupy the mid-range of sulfate–chloride ratios. This probably occurs through efficient replenishment of pore water sulfate and/or through the generation of sulfur redox intermediates, which promote pyrite formation via the polysulfide reaction pathway. In light of these results and in contrast to earlier models, we hypothesize that mild early Paleozoic bioturbation temporarily increased pyrite burial efficiency by stimulating higher sulfate reduction rates and increasing sedimentary sulfide retention. Compiled sulfur and carbon data from a geochemical database indicate that median sulfur-carbon ratios of fine-grained marine siliciclastic rocks increased from the Ediacaran through the Ordovician, then decreased and became much less variable from the Silurian onward. Thus, the Cambrian and Ordovician Periods may constitute a distinct interval of the Proterozoic-Phanerozoic transition in which bioturbation temporarily accelerated O2 buildup. This transition probably ended in the Silurian, when pO2 rose to sufficient levels to homogenize sedimentary carbon–sulfur cycling.

Enhancing predictive accuracy in social contagion dynamics via directed hypergraph structures

Evidence from both theoretical and empirical studies suggests that higher-order networks have emerged as powerful tools for modeling social contagions, such as opinion formation. In this article, we develop a model of social contagion on directed hypergraphs by considering the heterogeneity of individuals and environments in terms of reinforcing contagion effects. By distinguishing the directedness between nodes and hyperedges, we find that the bistable interval of the discontinuous phase transition decreases as the directedness strength decreases. Additionally, directed hypergraphs tend to generate bistable intervals when nodes with a large hyperdegree are more likely to adopt a specific opinion, as evidenced by simulations of directionality assignments for three sets of real networks. These findings provide two approaches to enhance the accuracy of predicting social contagion dynamics: one is to increase the stubbornness of all individuals, and the other is to prioritize increasing the stubbornness of highly influential individuals.

New methods of train traffic control

This article is written about a new concept of train traffic control. A topic of significant relevance in the field of organisational and safety aspects of train traffic. The existing system of train traffic control is based on the principles of application of field devices railway automation, and depending on their state driver provides movement or stopping of the train. Also on the monitoring panels, which are located in the control center, describes the state of floor devices, by them train dispatcher keeps track only the approximate location of the train. ETCS is based on the idea of continuous monitoring of the transport process using a combination of various technical means, thereby achieving a safe reduction in the transit interval, which means an increase in throughput. The ETCS is based on determining the location of the train, calculating the distance between trains, controlling the maximum permissible speed on the section, calculating the braking curve (depending on the speed over the distance traveled), comparing route data with the technical characteristics of the train. The requirements for ETCS devices are strict parameters of the accuracy of the navigation system: the error in determining the location of the eurobalance should not exceed ± 1 m, and the error of the odometers should not exceed ± 5% of the distance traveled.

DC-Link Dynamics Examination of the Parallel-Connected Three-Phase Inverters in Islanded and Grid-Connected Modes

This paper presents a comprehensive analysis of an AC microgrid setup, consisting of parallel three-phase inverters. It introduces a novel controller that integrates the tasks of controlling the DC-link voltage and implementing a current limiting approach. The design is informed by the characteristics of lead compensators and its main objectives are twofold: i) to regulate the DC-link voltage in order to minimize unwanted power exchange among the parallel inverters, and ii) to ensure the current-limiting capabilities of all inverters, regardless of the microgrid's operational state. This includes both standalone and grid-connected modes, voltage sags in the grid side, as well as transitional intervals between the two. In contrast to existing DC-link voltage control methods that do not incorporate a current limiting strategy, the proposed solution effectively restrains the dq axis current values in all operating conditions. This is crucial for preserving system stability, avoiding abrupt changes in DC-link voltage and current during sudden grid modifications and transitions. To validate the efficacy of the proposed controller, a series of simulations were carried out using Matlab/Simulink to evaluate its performance and compare it with an established method. The results explicitly demonstrate that the proposed controller successfully stabilizes the system, minimizes fluctuations in DC-link voltage, and restricts the dq axis current for each inverter without the potential of protection relay tripping.

Precision spectroscopy of iodine absorption lines near the 1S0-3P2 transition of Yb atoms at 507 nm

We performed Doppler-free spectroscopy on the P(40)52-0 and P(52)53-0 lines of molecular iodine (127I2) near the 1S0-3P2 metastable transition of Yb at 507 nm. The frequency instability of an external-cavity diode laser locked to the observed hyperfine transitions of the 127I2 lines reached a level below 1.0 × 10−12, at the average time τ of the measurement of >10 s. The absolute frequency of the laser locked to the hyperfine transitions was measured with an uncertainty of 8 kHz (fractionally 1.4 × 10−11) using an optical frequency comb. The hyperfine transition intervals were fitted to a four-term Hamiltonian to validate the measurements and calculate the hyperfine constants of the iodine lines. The observed 30 hyperfine transitions of the P(40)52-0 and P(52)53-0 lines of 127I2 can be used as optical frequency references to investigate the 1S0-3P2 transition of Yb atoms.

Pressure effects on molecular evolution: Differences between vitrinite and inertinite in coal

The difference between vitrinite and inertinite in coal has been regarded as the starting point, and the vitrinite and inertinite stripped from a coal sample were conducted by high-temperature (600 °C and 900 °C) and high-pressure (1.0, 1.5, and 2.0 GPa) experiments. The samples' molecular structure was examined with element analysis, Fourier-transform infrared spectroscopy, and X-ray diffraction. The results reveal that pressure has an inhibitory effect on the evolution of molecular structure at 600 °C, and the vitrinite shows a lower molecular structure evolution degree than inertinite. For the two macerals at 900 °C, with increasing pressure, the molecular structure parameters exhibit opposite regularities to those at 600 °C, and the vitrinite shows a higher molecular structure evolution degree than inertinite. The evolution rate of molecular structures caused by pressure in vitrinite remains consistent under different temperature conditions, whereas that in inertinite exhibits jumping changes. There must be a transition interval between 600 °C and 900 °C that can change the pressure from inhibiting coalification to promoting coalification. When the temperature exceeds the transition interval, pressure can accelerate the molecular structure evolution in vitrinite, causing it to catch up with and surpass the evolution degree of inertinite's molecular structure.

Effect of fully-grouted bolts on the failure behaviors of mine pillars: Insights from block-based FDEM modeling

In this study, the Voronoi-based breakable block model (VBBM) based on the combined finite-discrete element method (FDEM) is used to investigate the failure mechanism of mine pillars and the rock-rockbolt interactions. The mechanical parameters of grout-rock and grout-bolt interfaces of a fully-grouted bolt are calibrated via numerical pull-out tests. Then, uniaxial compression tests are carried out on the reinforced pillars. The kinetic energy release rate (KERR) and crack aperture (CA) are used to evaluate the reinforcement effect. The results revealed that the VBBM can effectively characterize the damage failure mechanisms of spalling on the pillar surface and conjugate shear failure in the core zone of the pillar and reproduce the pre-peak nonlinear deformation and post-peak pseudo-ductile behaviors. The passive confining pressure generated by rockbolts is activated only when the rock mass produces sufficient deformation, and the constraints generated by different numbers of rockbolts can only affect the post-peak behavior of the pillar. There is a gradient feature in the internal deformation of the pillar from the shallow surface to the core. If the rockbolt density meets the strain demand, then rockbolts can delay the inward expansion of cracks by generating local constraints and can effectively fix the spalling rock blocks. With increasing support pressure, the CA and KERR exhibit a decreasing trend and strong power-exponential relationships with support pressure, indicating that there is a transition interval of support pressure and an optimal value for setting the rockbolt density.

Machine learning of the chemical elements for enhanced interpretation of depositional environments: Upper Jurassic strata case study in central Saudi Arabia

To explore how machine learning (ML) techniques can enhance the interpretation of depositional environments using chemical elemental data, this study analyzes data from 156 shallow marine strata samples. Several advanced machine learning (ML) techniques were integrated to predict lithofacies and stratigraphic units of shallow marine carbonate strata, focusing on the Arab-D reservoir equivalent outcrops in Central Saudi Arabia. Utilizing a detailed geochemical dataset comprising major, trace, and rare earth elements, we aimed to determine the feasibility of using chemical elemental data in sedimentary geology for predictive modeling. The studied strata are categorized into two lithological units based on depositional settings: one unit comprises rocks that dominantly deposited below the storm wave base with a single lithofacies association, whereas the other includes rocks dominantly deposited above the storm wave base, and consists of two lithofacies associations. The study demonstrates the efficacy of ML algorithms in distinguishing these two lithological units, with a minimum prediction accuracy of 76%. Four ML techniques, including K-nearest neighbors (KNN); random forest classifier (RFC); gradient boosting classifier (GBC); and multi-layer perceptron neural network (MLP-NN) were used, two of them (RFC and GBC) achieved 89% and 92% prediction accuracy. However, a slightly poorer performance was observed in predicting fine-scale lithofacies associations of these lithological units, especially for the lithofacies association representing a transitional interval between the two lithofacies units. Expanding the scope of the study, we tested the ML models against geochemically similar strata from the Oligocene shallow marine reef carbonates. These strata are globally comparable and provide an external validation for the predictive models developed from the Saudi Arabian dataset. GBC and RFC maintained a higher accuracy level than KNN and MLP, demonstrating their robustness and transferability across diverse geological settings. Based on these results, the study underscores the significance of specific oxides and elements as distinctive geochemical markers, elucidating the environmental conditions of the depositional environments and their deposits. This research advances the application of ML in interpreting the depositional environments of shallow marine strata using elemental data, as the majority of the existing researches focus on employing unsupervised machine learning for cluster analysis.