Stress Map Research Articles

Implementation of Principal Component Analysis (PCA)/Singular Value Decomposition (SVD) and Neural Networks in Constructing a Reduced-Order Model for Virtual Sensing of Mechanical Stress.

This study presents the design and validation of a numerical method based on an AI-driven ROM framework for implementing stress virtual sensing. By leveraging Reduced-Order Models (ROMs), the research aims to develop a virtual stress transducer capable of the real-time monitoring of mechanical stresses in mechanical components previously analyzed with high-resolution FEM simulations under a wide range of multiple load scenarios. The ROM is constructed through neural networks trained on Finite Element Method (FEM) outputs from multiple scenarios, resulting in a simplified yet highly accurate model that can be easily implemented digitally. The ANN model achieves a prediction error of MAEtest=(0.04±0.06) MPa for the instantaneous mechanical stress predictions, evaluated over the entire range of stress values (0 to 5.32 MPa) across the component structure. The virtual sensor is capable of producing a quasi-instantaneous, detailed full stress map of the component in just 0.13 s using the ROM, for any combination of 4-load inputs, compared to the 6 min and 31 s required by the FEM. Thus, the approach significantly reduces computational complexity while maintaining a high degree of precision, enabling efficient real-time monitoring. The proposed method's effectiveness is demonstrated through rigorous ROM validation, underscoring its potential for stress control. This precise AI-driven procedure opens new horizons for predictive maintenance strategies centered on stress cycle monitoring.

The Lattice Strain Distribution in GexSn1-x Micro-Disks Investigated at the Sub 100-nm Scale

The local lattice distortion in a crystal, the lattice strain, greatly influences the physical mechanisms underlying the operating principles of semiconductor devices. For example, strain is widely used in the bandgap engineering of group IV-based optoelectronic devices to improve their performance. In the case of GeSn-based light emitters, optimization of the lattice strain allowed the demonstration of optically pumped lasing at room temperature [1] and cw operation in an electrically pumped µ-disk laser [2], thanks to its beneficial effect on the "directness" of the bandgap, leading to increased material gain. It is therefore of paramount importance to characterize the strain with high sensitivity and sub-micron spatial resolution.Here we show how scanning X-ray diffraction microscopy, a recently developed model-free method based on synchrotron radiation [3,4], can be used to fully determine the landscape of mechanical deformation and stoichiometry fluctuation in a lithographically fabricated Ge1-xSnx/Ge suspended µ-disk, a structure of the same type as that used to demonstrate the first GeSn laser [5].The full strain tensor of the entire microstructure, including all normal and shear components, is tomographically reconstructed with a lateral resolution of less than 100 nm and a sensitivity to strain variations of the order of 10-4. By comparing the lattice deformation in different sections of the microdisk, we observe a marked difference between the central pillar region in contact with the virtual Ge substrate and the free-standing outer rim where the Ge layer has been removed. Interestingly, although the misfit dislocation network at the GeSn/Ge relaxed heterointerface in the rim region has been removed during the fabrication process, we observe that a "fossilized" footprint of the dislocations is still present in the strain landscape of the layer. We attribute this to stoichiometric fluctuations that we measure in the Ge1-xSnx alloy generated by dislocation-driven strain fields during epitaxial growth, which are unaffected by etching and in turn generate a local strain field.We then exploit the symmetries of both the microdisk and the Ge1-xSnx material system itself. This allows us, for the first time, to calculate maps of the surface normal stress in an alloyed epitaxial thin film, which is traditionally difficult to impossible to disentangle from stoichiometric fluctuations in diffraction-based data, and is a key piece of information to evaluate in epitaxial layer growth.We complement the synchrotron experiments with electron microscopy and dedicated finite element method (FEM) simulations of both elastic and plastic relaxation processes in the model system, finding excellent agreement between experiment and theory. Furthermore, the effects of strain on the band structure are predicted in the light of the measured local variations in strain and composition.[1] A Elbaz, et al. Nature Photon. 14, 375 (2020)[2] L. Siedel et al. Nature, submitted (2024)[3] C. Corley-Wiciak et al. ACS Appl. Mater. & Interfaces 15, 3119 (2023)[4] C. Richter et al. Phys. Rev. Applied 18, 064015 (2022)[5] S Wirths, et al. Nature Photonics 9, 88 (2015)

Innovative computational model for optimal deep coal mining under large-scale crustal stress conditions

Understanding and controlling the ground stress in deep coalfield mining is crucial for ensuring mine safety and efficiency. This study aims to address two unresolved scientific issues in ground stress research: the selection of optimal excavation plans and the large-scale rapid acquisition of ground stress data. A novel computational model is proposed for key rock layer control under different crustal stress conditions. The model considers the complexity and uncertainty of ground stress distribution by simplifying the key rock strata into a fixed-fixed beam model and calculating their safety through mechanical methods. Introducing an innovative approach for acquiring large-scale stress fields using GPS data. By inverting large-scale strain fields in the coalfield area, combined with World Stress Map (WSM) and measured data, accurate stress fields are obtained. The proposed optimal excavation plan can be applied to various coalfield locations worldwide, providing a scientific basis for safe and efficient mining operations. Additionally, the innovative use of GPS data in obtaining large-scale stress fields offers a valuable tool for assessing ground stress variation.

Enhanced digital twin framework for real-time prediction of fatigue damage on semi-submersible platforms under long-term multi-sea conditions

As the development of offshore oil and gas resources progresses into deeper waters, the impact on marine structures becomes increasingly severe, resulting in significant structural damage. This highlights the importance of health monitoring for marine structures. The emergence of digital twin technology in ocean engineering has greatly advanced the development of marine structure monitoring technologies, improving the intelligence and real-time capabilities of structural health monitoring. This paper proposes an innovative data-driven digital twin framework, applied to the real-time fatigue damage prediction of the semi-submersible platform under long-term multi-sea conditions. Notably, this study introduces a novel stress twinning method along with a high-precision post-processing module that combines field monitoring data with high-fidelity simulation model results. This integration establishes a bidirectional connection between the physical structure and its digital counterpart, enabling real-time mapping of structural hotspot stresses and more accurate fatigue damage predictions. The proposed framework was validated on the semi-submersible platform in the South China Sea, and the results proved its practicality and transformative potential in offshore structure management.

Ecophysiological variables retrieval and early stress detection: insights from a synthetic spatial scaling exercise

ABSTRACT The ability to access physiologically driven signals, such as surface temperature, photochemical reflectance index (PRI), and sun-induced chlorophyll fluorescence (SIF), through remote sensing (RS) are exciting developments for vegetation studies. Accessing this ecophysiological information requires considering processes operating at scales from the top-of-the-canopy to the photosystems, adding complexity compared to reflectance index-based approaches. To investigate the maturity and knowledge of the growing RS community in this area, COST Action CA17134 SENSECO organized a Spatial Scaling Challenge (SSC). Challenge participants were asked to retrieve four key ecophysiological variables for a field each of maize and wheat from a simulated field campaign: leaf area index (LAI), leaf chlorophyll content (C ab), maximum carboxylation rate (V cmax,25), and non-photochemical quenching (NPQ). The simulated campaign data included hyperspectral optical, thermal and SIF imagery, together with ground sampling of the four variables. Non-parametric methods that combined multiple spectral domains and field measurements were used most often, thereby indirectly performing the top-of-the-canopy to photosystem scaling. LAI and C ab were reliably retrieved in most cases, whereas V cmax,25 and NPQ were less accurately estimated and demanded information ancillary to RS imagery. The factors considered least by participants were the biophysical and physiological canopy vertical profiles, the spatial mismatch between RS sensors, the temporal mismatch between field sampling and RS acquisition, and measurement uncertainty. Furthermore, few participants developed NPQ maps into stress maps or provided a deeper analysis of their parameter retrievals. The SSC shows that, despite advances in statistical and physically based models, the vegetation RS community should improve how field and RS data are integrated and scaled in space and time. We expect this work will guide newcomers and support robust advances in this research field.

MULTIAXIAL AND UNIAXIAL FATIGUE ANALYSIS OF A MOORING CHAINS FOR AN OFFSHORE FLOATING WIND TURBINE

This paper presents the fatigue study (uniaxial fatigue and multiaxial fatigue) of mooring chains for a floating wind turbine (FWT). The operating principle of a floating offshore wind turbine (FOWT) and general information on uniaxial and multiaxial fatigue are presented, together with a reminder of the standards governing fatigue in the offshore sector. Uniaxial fatigue damage and service life calculations are carried out for various loading conditions and sea states. The finite element method is carried out using ANSYS software in order to estimate the best mapping of stresses and strains on the structure of the mooring chain. Finally, a simulation was also carried out using usingMatlab software to calculate the damage and multiaxial fatigue life. Comparison of the two analyses shows that uniaxial fatigue analysis minimises long-term damage and that multiaxial fatigue should be preferred for estimating the durability of offshore structures under extreme loading.

Determination and Application of Stress States Based on Finite Element Techniques: A Case Study of the Longmaxi Formation in the Luzhou Block, Sichuan Basin.

Knowledge of the present-day in situ stress field (PIS) has important theoretical and practical significance for shale gas exploration and development. The Wufeng-Longmaxi Formation in the Luzhou Block serves as the main reservoir of marine shale production in southern China. However, there is no clear understanding of PIS in the Luzhou area, which leads to a series of production problems. To investigate the PIS of deep shale reservoirs in Luzhou, experimental and finite element methods (FEMs) were used. Data obtained from imaging logging data, well deviation data, multipole array acoustic logging (XMAC), and world stress map were used to determine the orientation of the horizontal maximum principal stress (S Hmax). Additionally, acoustic emission experiments were employed to determine the magnitude of three principal stresses. Based on FEM, with the stress of a single well as a constraint, a three-dimensional (3D) stress field model was developed. The results show that the orientation of S Hmax varies from 90 to 120 °E. Further, there are significant differences in stress regimes across the region, with strike-slip/reverse faulting stress regime (S Hmax > S v ≈ S hmin) in the northern region and strike-slip stress regime in the southern region (S Hmax > S v > S hmin). In addition, geomechanical evaluations of wellbore stability and natural activation of fractures were performed. The Luzhou Block mainly develops two groups of natural fractures (NE-SW trending and NW-SE trending), with NW-SE trending being the dominant fracture development orientation. During the fracturing operation, a pore pressure increment larger than 50 MPa is conducive to maintaining a high opening ratio of the reservoir and improving the gas production efficiency. Horizontal wells drilled in the direction of maximum horizontal principal stress in the Wufeng-Longmaxi Formation reduce the probability of wellbore instability. The research results provide a reference for the effective development of deep shale gas reservoirs in southern Sichuan.

Force and energy transmission at the brain-skull interface of the minipig in vivo and post-mortem

The brain-skull interface plays an important role in the mechano-pathology of traumatic brain injury (TBI). A comprehensive understanding of the mechanical behavior of the brain-skull interface in vivo is significant for understanding the mechanisms of TBI and creating accurate computational models. Here we investigate the force and energy transmission at the minipig brain-skull interface by non-invasive methods in the live (in vivo) and dead animal (in situ). Displacement fields in the brain and skull were measured in four female minipigs by magnetic resonance elastography (MRE), and the relative displacements between the brain and skull were estimated. Surface maps of deviatoric stress, the apparent mechanical properties of the brain-skull interface, and the net energy flux were generated for each animal when alive and at specific times post-mortem. After death, these maps reveal increases in relative motion between brain and skull, brain surface stress, stiffness of brain-skull interface, and net energy flux from skull to brain. These results illustrate the ability to study both skull and brain mechanics by MRE; the observed post-mortem decrease in the protective capability of the brain-skull interface emphasizes the importance of measuring its behavior in vivo.

WRF-HEATS coupling: Incorporating human behaviors and city topography into urban heat stress evaluation

Urban human thermal stress can be inaccurately estimated along with less-understood heat heterogeneity due to the absence of high-resolution meteorological information and realistic human behavior representation. To this end, we coupled a regional climate model (weather research and forecasting model, WRF) and a human energy balance model (human-environment adaptive thermal stress model, HEATS) to predict pedestrian's dynamic thermal stress at a neighborhood scale. The WRF-human coupling system resolves human-environment heat exchanges based on meteorological and topographical information with the consideration of dynamic human activities. The coupling system has been tested and utilized to study dynamic heat stress in a typical hot, humid, and mountainous city, Hong Kong. Our results revealed widespread heat heterogeneity with up to 7 °C difference in Physiological Subjective Temperature (PST) in the core urban area, and extreme heat exposure (up to 45 °C PST) in calm-wind zones at noon. Heat stress can be further aggregated considering realistic human behaviors such as extra clothing (e.g., protective facemask during pandemics) and physical exercise (e.g., walking along inclined terrain). Optimal-thermal-comfort routes have been designed and suggested based on the simulated neighborhood-scale heat stress map.

Crustal seismicity and updated stress mapping in the Bolivian Orocline, Central Andes

The Central Andes region, with significant seismic activity, has distinct faulting mechanisms across its varied topography. Notably, the sub-Andean province predominantly features reverse faulting, whereas the high Andean plateau shows a predominance of normal and strike-slip faults. Despite the importance of this extensive orogenic plateau, Bolivia remains under-documented in seismic studies. We used data from recently installed seismic stations in Bolivia and regional stations in Brazil to determine 13 new focal mechanisms of shallow crustal earthquakes in Bolivia, some of them felt in major cities. Employing probabilistic full waveform moment tensor inversion and P-wave polarities, we mapped the stress distribution across the Central Andes. The main patterns of faulting mechanisms were: reverse faulting along the NW-SE trending sub-Andean belt north of the Orocline (north of Cochabamba) with NE-SW compression; reverse faulting along the N-S trending sub-Andean belt south of the Orocline (south of Santa Cruz) with ∼ E-W oriented compression; strike-slip faulting within the Eastern Cordillera with NE-SW P axes. The results indicate that the sub-Andean belt experiences compressional forces perpendicular to the front of the Andean plateau, arising from both the spreading stresses of the plateau and the broader plate-wide compression. On the other hand, the high plateau (Altiplano) is characterized by normal and strike-slip mechanisms, suggesting a dynamic equilibrium between local extensional gravitational stresses and regional compressional forces due to the Nazca plate convergence.

Spatially varying stress regime in the southern Junggar Basin, NW China

The southern Junggar Basin in NW China is an important tectonic unit in the region of the Tibetan Plateau and has been the focus of considerable research into its tectonic processes and geodynamic setting. However, the relationship between deep structural deformation and stress in this region remains unclear. This study investigates the Gaoquan and Hutubi anticlines in the southern Junggar Basin using three-dimensional geophysical data and a finite-element numerical simulation to examine the crustal stress distribution and stress regime at depths of up to 7 km. Numerical simulation results indicate that the stress regime in the southern Junggar Basin changes from west to east. In the western part of the region, including the Gaoquan anticline at depths of 4900–6100 m, the maximum horizontal principal stress shows a peak of 140–200 MPa, the minimum horizontal principal stress is 110–170 MPa, and the vertical principal stress is 115–175 MPa, indicating a mixed stress regime incorporating both compression and strike-slip components. In the eastern part of the region, including the Hutubi anticline at depths of 5400–7800 m, the maximum horizontal principal stress shows a peak of 160–280 MPa, the minimum horizontal principal stress is 155–250 MPa, and the vertical principal stress is 125–215 MPa, indicating a compressive stress regime. The stress magnitude and orientation are affected by the presence of faults and depth in the crust. Combining these results with the regional tectonic setting, it is considered that the geometrical relationship between pre-existing faults and the current stress field is the main control on the west–east differentiation in the stress regime, with spatial variations in the mechanical parameters of the crust and the pressure coefficient being secondary factors. These results provide insights into the relationship between stress and deformation, and support the updated version of the World Stress Map database.

Thin Liquid Film View and Shear Stress During the Sliding of Air Bubbles on Tilted Plates.

The challenge when studying the impact and sliding of free-rising air bubbles on tilted surfaces is an experimental limitation in obtaining the film thickness of thin liquid film (TLF) during the bubbles' sliding on tilted surfaces. In this work, spatiotemporal evolution in the film thickness of the moving TLF between a sliding air bubble and a tilted plate was monitored by using a two-wavelength synchronized reflection interferometry microscopy (SRIM) technique. The evolution of the film thickness was directly determined from a timed series of monochromatic interference fringes recorded simultaneously at two different wavelengths. From the film thickness profile, a shear stress map at a given time was determined at different bubble sizes and inclination angles. Results showed that the film thickness of TLFs during the bubbles' sliding on tilted surfaces was in the range of 300-1200 nm, depending on bubble size and tilting angles. Sliding of air bubbles on tilted plates over a thin gap with a few hundred nanometers thickness yielded shear stress in the order of 10-50 Pa. Both the larger bubble size and higher tilting angles yielded a higher shear stress. Experimental results were quantitatively compared to numerical results obtained using the Reynolds lubrication theory. A good match between the two results was achieved. Numerical results suggested that a maximum shear stress exerted on a tilted plate occurred at a 25° tilting angle. This is the first time that the spatiotemporal evolution of TLF during bubbles' sliding on tilted surfaces has been achieved, and the shear stress exerted on the tilted surface has been directly determined.

Development, calibration and validation of impact-specific cervical spine models: A novel approach using hybrid multibody and finite-element methods

Background and Objective:Spinal cord injuries can have a severe impact on athletes’ or patients’ lives. High axial impact scenarios like tackling and scrummaging can cause hyperflexion and buckling of the cervical spine, which is often connected with bilateral facet dislocation. Typically, finite-element (FE) or musculoskeletal models are applied to investigate these scenarios, however, they have the drawbacks of high computational cost and lack of soft tissue information, respectively. Moreover, material properties of the involved tissues are commonly tested in quasi-static conditions, which do not accurately capture the mechanical behavior during impact scenarios. Thus, the aim of this study was to develop, calibrate and validate an approach for the creation of impact-specific hybrid, rigid body - finite-element spine models for high-dynamic axial impact scenarios. Methods:Five porcine cervical spine models were used to replicate in-vitro experiments to calibrate stiffness and damping parameters of the intervertebral joints by matching the kinematics of the in-vitro with the in-silico experiments. Afterwards, a five-fold cross-validation was conducted. Additionally, the von Mises stress of the lumped FE-discs was investigated during impact. Results:The results of the calibration and validation of our hybrid approach agree well with the in-vitro experiments. The stress maps of the lumped FE-discs showed that the highest stress of the most superior lumped disc was located anterior while the remaining lumped discs had their maximum in the posterior portion. Conclusion:Our hybrid method demonstrated the importance of impact-specific modeling. Overall, our hybrid modeling approach enhances the possibilities of identifying spine injury mechanisms by facilitating dynamic, impact-specific computational models.

Multi-modal, Label-free, Optical Mapping of Cellular Metabolic Function and Oxidative Stress in 3D Engineered Brain Tissue Models.

Brain metabolism is essential for the function of organisms. While established imaging methods provide valuable insights into brain metabolic function, they lack the resolution to capture important metabolic interactions and heterogeneity at the cellular level. Label-free, two-photon excited fluorescence imaging addresses this issue by enabling dynamic metabolic assessments at the single-cell level without manipulations. In this study, we demonstrate the impact of spectral imaging on the development of rigorous intensity and lifetime label-free imaging protocols to assess dynamically over time metabolic function in 3D engineered brain tissue models comprising human induced neural stem cells, astrocytes, and microglia. Specifically, we rely on multi-wavelength spectral imaging to identify the excitation/emission profiles of key cellular fluorophores within human brain cells, including NAD(P)H, LipDH, FAD, and lipofuscin. These enable development of methods to mitigate lipofuscin's overlap with NAD(P)H and flavin autofluorescence to extract reliable optical metabolic function metrics from images acquired at two excitation wavelengths over two emission bands. We present fluorescence intensity and lifetime metrics reporting on redox state, mitochondrial fragmentation, and NAD(P)H binding status in neuronal monoculture and triculture systems, to highlight the functional impact of metabolic interactions between different cell types. Our findings reveal significant metabolic differences between neurons and glial cells, shedding light on metabolic pathway utilization, including the glutathione pathway, OXPHOS, glycolysis, and fatty acid oxidation. Collectively, our studies establish a label-free, non-destructive approach to assess the metabolic function and interactions among different brain cell types relying on endogenous fluorescence and illustrate the complementary nature of information that is gained by combining intensity and lifetime-based images. Such methods can improve understanding of physiological brain function and dysfunction that occurs at the onset of cancers, traumatic injuries and neurodegenerative diseases.

Prognostic validity of coronary flow reserve (CFR)-derived mapping-stress MRI in the risk stratification of suspected or known CAD patients

PurposeAim of our study is to evaluate the prognostic value of T1 stress mapping in suspected or known- CAD patients.Materials and methodsIn this retrospective study, there were 34 patients with known CAD. Mean follow-up time was 30.9 months (95% CI 29.49–32.31). All eligible participants were re-called for an on-site interview and we evaluated Primary endpoints like all Major Adverse Cardiac Events (MACE) and Secondary endpoints (arrhythmias and all cardiac causes of clinical worsening).ResultsOur general population of patients was split into responders and nonresponders based on T1 Mapping response. The T1 values were not statistically significant when compared based on collected MACE; however, when compared to secondary outcomes, there were significant differences in non-responders patients (p-value 0.001).ConclusionThe microcirculation defect can be identified more effectively and accurately with T1 mapping than conventional qualitative evaluation. T1 mapping assumes a prognostic and therapeutic significance in stratifying the risk of patients with microvascular angina who have shown secondary outcomes.

Microstructure and stress mapping in 3D at industrially relevant degrees of plastic deformation

Strength, ductility, and failure properties of metals are tailored by plastic deformation routes. Predicting these properties requires modeling of the structural dynamics and stress evolution taking place on several length scales. Progress has been hampered by a lack of representative 3D experimental data at industrially relevant degrees of deformation. We present an X-ray imaging based 3D mapping of an aluminum polycrystal deformed to the ultimate tensile strength (32% elongation). The extensive dataset reveals significant intra-grain stress variations (36 MPa) up to at least half of the inter-grain variations (76 MPa), which are dominated by grain orientation effects. Local intra-grain stress concentrations are candidates for damage nucleation. Such data are important for models of structure-property relations and damage.

Compressible Hollow Microlasers in Organoids for High-Throughput and Real-Time Mechanical Screening.

Mechanical stress within organoids is a pivotal indicator in disease modeling and pharmacokinetics, yet current tools lack the ability to rapidly and dynamically screen these mechanics. Here, we introduce biocompatible and compressible hollow microlasers that realize all-optical assessment of cellular stress within organoids. The laser spectroscopy yields identification of cellular deformation at the nanometer scale, corresponding to tens of pascals stress sensitivity. The compressibility enables the investigation of the isotropic component, which is the fundamental mechanics of multicellular models. By integrating with a microwell array, we demonstrate the high-throughput screening of mechanical cues in tumoroids, establishing a platform for mechano-responsive drug screening. Furthermore, we showcase the monitoring and mapping of dynamic contractile stress within human embryonic stem cell-derived cardiac organoids, revealing the internal mechanical inhomogeneity within a single organoid. This method eliminates time-consuming scanning and sample damage, providing insights into organoid mechanobiology.

A new automated procedure to obtain reliable moment tensor solutions of small to moderate earthquakes (3.0 ≤ M ≤ 5.5) in the Bayesian framework

SUMMARY The complete catalogue of moment tensor (MT) solutions is essential for a wide range of research in solid earth science. However, the number of reliable MT solutions for small to moderate earthquakes (3.0 ≤ M ≤ 5.5) is limited due to uncertainties arising from data and theoretical errors. In this study, we develop a new procedure to enhance the resolvability of MT solutions and provide more reliable uncertainty estimates for these smaller to moderate earthquakes. This procedure is fully automatic and efficiently accounts for both data and theoretical errors through two sets of hybrid linear–non-linear Bayesian inversions. In the inversion process, the covariance matrix is estimated using an empirical approach: the data covariance matrix is derived from the pre-event noise and the theoretical covariance matrix is derived from the residuals of the initial solution. We conducted tests using synthetic data generated from the 3-D velocity model and interference from background seismic noise. The tests found that using a combination of the non-Toeplitz data covariance matrix and the Toeplitz theoretical covariance matrix improves the solution and its uncertainties. Test results also suggest that including a theoretical covariance matrix when analysing MT in complex tectonic regions is essential, even if we have the best 1D velocity model. The application to earthquakes in the northern region of the Banda Arc resulted in the first published Regional Moment Tensor (RMT) catalogue, containing more than three times the number of trusted solutions compared to the Global Centroid Moment Tensor (GCMT) and the Indonesian Agency for Meteorology Climatology and Geophysics Moment Tensor (BMKG-MT) catalogue. The comparison shows that the trusted solutions align well with the focal mechanism of the GCMT and BMKG-MT, as well as with the maximum horizontal stress of the World Stress Map, and tectonic conditions in the study area. The newly obtained focal mechanisms provide several key findings: (i) they confirm that the deformation in the northern and eastern parts of Seram Island is influenced by oblique intraplate convergence rather than by the subduction process; (ii) they validate the newly identified Amahai Fault with a greater number of focal mechanisms and (iii) they reveal an earthquake Mw 4.7 with the same location and source mechanism 6 yr before the 2019 Ambon-Kairatu earthquake (Mw 6.5) which occurred on a previously unidentified fault.

Unveiling urban heat: harnessing personal weather stations for enhanced daily mapping of heat stress across North Carolina

Unveiling urban heat: harnessing personal weather stations for enhanced daily mapping of heat stress across North Carolina

Load-dependent optical coherence tomography attenuation imaging: How tissue mechanics can influence optical scattering

Mechanical load imparted to tissue, for example via handheld imaging probes, leads to tissue deformation, altering the distribution of tissue microstructure and, consequently, attenuation of light and image formation in optical imaging. In mechanically heterogeneous tissue, the load can result in spatially varying deformation and, therefore, spatially varying changes in the attenuation of light, which may provide additional image contrast. To investigate this potential, an assessment of the spatially resolved impact of mechanical deformation of the tissue on optical imaging is critical; however, it is challenging to incorporate stress mapping into optical imaging without obscuring the detection of photons. To address this, we present the novel integration of stress imaging using optical palpation with attenuation imaging based on optical coherence tomography (OCT). The method was implemented using a compliant silicone sensor incorporated into a custom handheld OCT probe, providing two-dimensional stress imaging with concurrent attenuation imaging. Attenuation imaging with varying mechanical loads was demonstrated on 19 tissue regions acquired from eight freshly excised human breast specimens. The results demonstrated distinct characteristics for different breast tissue types: benign stroma showed relatively large increases in attenuation (e.g., ∼0.3 to 0.4 mm−1/kPa) over a low stress range (∼2 to 10 kPa), while cancerous tissue showed markedly small increases in attenuation (e.g., ∼0.005 to 0.02 mm−1/kPa) mainly over a medium to high stress range (∼10 to 90 kPa). The integration of stress imaging with attenuation imaging provided a pilot assessment of the spatially resolved impact of tissue mechanical heterogeneity on optical attenuation, providing novel image contrast by encoding variations in mechanical properties on optical attenuation in tissue.