Emission Tomography Research Articles

Heterogeneity induced fracture characterization of concrete under fatigue loading using digital image correlation and acoustic emission techniques

Understanding the fatigue failure mechanisms in concrete is complex and remains an area of ongoing investigation. Material heterogeneity, along with the size effect, plays a significant role in specifying the crack propagation behaviour and fatigue life in case of repetitive loading conditions. In this study, the influence of material heterogeneity on the fatigue behaviour of concrete has been examined. Three different-size beam specimens with varying heterogeneity (aggregate sizes) have been considered to investigate various fracture characteristics under repetitive load conditions. Acoustic emission and digital image correlation techniques have been employed to analyse crack growth behaviour. The results revealed that stiffness degradation and crack propagation rates are faster for the specimens with smaller aggregate sizes compared to the larger aggregate size specimens of the same depth. Moreover, the fatigue life and effective crack length at failure are also higher in the case of larger aggregate sizes compared to smaller ones. Therefore, a heterogeneity-adjusted, analytical model of fatigue crack growth has been proposed. Further, the AE parameters have been utilized to characterize the tensile and shear crack dominance in different stages of fatigue crack propagation. The outcome of this study can be utilized to anticipate the crack propagation behaviour and residual fatigue life for any combination of specimen size and aggregate size.

Failure Mechanism and Control Mechanism of Intermittent Jointed Rock Bridge Based on Acoustic Emission (AE) and Digital Image Correlation (DIC).

Deep foundation pit excavation is an important way to develop underground space in congested urban areas. Rock bridges prevent the interconnection of joints and control the deformation and failure of the rock mass caused by excavation for foundation pits. However, few studies have considered the acoustic properties and strain field evolution of rock bridges. To investigate the control mechanisms of rock bridges in intermittent joints, jointed specimens with varying rock bridge length and angle were prepared and subjected to laboratory uniaxial compression tests, employing acoustic emission (AE) and digital image correlation (DIC) techniques. The results indicated a linear and positive correlation between uniaxial compressive strength and length, and a non-linear and negative correlation with angle. Moreover, AE counts and cumulative AE counts increased with loading, suggesting surges due to the propagation and coalescence of wing and macroscopic cracks. Analysis of RA-AF values revealed that shear microcracks dominated the failure, with the ratio of shear microcracks increasing as length decreased and angle increased. Notably, angle exerted a more significant impact on the damage form. As length diminished, the failure plane's transition across the rock bridge shifted from a complex coalescence of shear cracks to a direct merger of only coplanar shear cracks, reducing the number of tensile cracks required for failure initiation. The larger the angle, the higher the degree of coalescence of the rock bridge and, consequently, the fewer tensile cracks required for failure. The decrease of length and the increase of angle make rock mass more fragile. The more inclined the failure mode is to shear failure, the smaller the damage required for failure, and the more prone the areas is to rock mass disaster. These findings can provide theoretical guidance for the deformation and control of deep foundation pits.

Measurement of 3D joint surface morphology and estimation for shear mechanical behavior: A theoretical model and experimental investigation

The majority of rock engineering instabilities are primarily due to shear slips and failures on the joint surfaces, and the measurement of joint surface morphology is crucial for shear strength evaluation. In this study, the high-precision 3D laser scanner was first used to characterize and digitally reconstruct the surface morphology of various joints. The evaluation method of joint surface roughness was modified according to the 2D profile data and shear direction. Then, the effects of normal stress and initial joint roughness coefficient on the shear mechanical behavior were investigated by experimental method. The damage evolution characteristics and failure mechanism of the joint surface are analyzed by acoustic emission monitoring and image binarization calculations. The research results indicate that as the normal stress and initial joint roughness coefficient increase, the peak shear stress and shear displacement, residual strength, and cumulative AE counts of rock joints display an increasing trend. Based on the evolution of mechanical parameters, a new mechanical model of rock joints to predict shear strength and deformation was developed, which was validated by comparing the theoretical prediction curves with test results. A good concordance was achieved between the shear test and theoretical results, indicating that the developed model can effectively predict the shear strength and deformation of joint surfaces under different normal stress and roughness. This research results are expected to provide a valuable guidance for early warning and evaluation of geological disasters.

Improvement of AC Conditioning Effect in Vacuum by High Frequency Voltage

To improve the dielectric strength in vacuum, spark conditioning through repetitive breakdowns by AC or impulse voltage is an effective method. AC conditioning at commercial power frequencies has been widely used due to its cost‐effectiveness, but the breakdown voltage after AC conditioning is generally lower compared to impulse conditioning. We have confirmed that multiple breakdowns occur successively in a half cycle of AC voltage application. It is considered that the multiple breakdowns are harmful for conditioning and triggered due to the previous breakdown in the same half cycle. In this paper, we discuss dielectric strength improvement by high frequency AC conditioning and how the multiple breakdowns are induced. We experimentally confirmed that the AC conditioning effect is improved by increasing the frequency of AC voltage for different applied AC conditioning voltages in a sphere‐plane electrode system. We focused on the breakdown position from the light emission images during AC conditioning to investigate whether the multiple breakdowns were induced or affected by the previous breakdown. We found that the multiple breakdowns occurred close to the previous breakdown position. The multiple breakdowns would be induced by the collision of metal particles due to the previous breakdown with the counter electrode. These breakdowns do not contribute to removing protrusion and would lead to damage to the electrode surface. The increasing frequency of AC conditioning would suppress the multiple breakdowns and improve the dielectric strength in vacuum. © 2024 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Shear Performance and Damage Characterization of Prefabricated Basalt Fiber Reactive Powder Concrete Capping Beam Formwork Structure

Basalt Fiber Reactive Powder Concrete (BFRPC) semi-prefabricated composite capping beam structures can effectively improve the shortcomings of ordinary concrete capping beams' construction difficulties and insufficient bearing capacity. In this study, with the objective of analyzing the shear damage and damage characteristics of a prefabricated BFRPC capping beam formwork, structural damage tests under different levels of loading were carried out to obtain the mechanical parameters of key nodes. Acoustic emission (AE) and Digital Image Correlation (DIC) techniques were used to acoustically and visually characterize the formwork damage. The research results showed that the damage stage of the capping beam formwork was divided, and an early damage warning method was proposed based on the acoustic parameters. Using the DIC technique to identify the crack width evolution pattern during the shear process, it was found that the cracks expanded steadily as the load increased. Combining the experimental and simulation results as well as the Subdivision Superposition Theory, a half-open stirrup strength discount factor β was introduced and suggested to take a value of 0.79. The formula for calculating the shear capacity of BFRPC capping beam formwork is proposed to provide a theoretical basis for its application in prefabricated assembled structures.

Analysis of damage and fracture characteristics for concrete subjected to cryogenic freeze-thaw cycles: An acoustic emission and digital image correlation study

This study examines concrete's performance under cryogenic (−170 °C) freeze-thaw cycles (CFTCs), inspired by the development of all-concrete liquefied natural gas (ACLNG) tanks. Focusing on plain concrete (PC) and concrete with 3 % volume content steel fiber (SFRC3), the impact of fibers and moisture content on concrete's damage and failure characteristics pre and post cryogenic exposure is investigated. The compressive strength variation laws of concrete before and after 10 CFTCs were summarized in air-dried and water-saturated condition. Acoustic emission (AE) and digital image correlation (DIC) techniques were employed in the study to delineate the variances in failure process and fracture characteristics attributed to cryogenic exposure. Findings indicate a decline in the compressive strength of both PC and SFRC3 post exposure, more pronounced in water-saturated condition. Post-cryogenic exposure, AE signals exhibit decreased activities. The failure process of concrete is categorized into four stages based on the trends of severity index Sr and historical index Hs, both of which diminished, reflecting reduced signal strength and rate of change. AE frequency-amplitude characteristics differs between PC and SFRC3 during failure, with significant reduction in high frequency signals in SFRC3, suggesting weakened fiber-matrix bonding and increased fracture scale. The rise in the number of shear cracks nearing failure is discerned from variations in rise angle (RA) and average frequency (AF), proposing the ratio of RA to AF equal to 15 as a precursor of concrete failure. The DIC analysis shows increased crack width and numbers in both PC and SFRC3 post exposure, along with localized spalling. SFRC3 can still effectively maintain the integrity without complete breakage despite severe cracks are generated.

Runaway electron plateau current profile reconstruction from synchrotron imaging and Ar-II line polarization angle measurements in DIII-D

Current profile reconstructions are obtained for high current ( Ip≃550 kA) post-disruption runaway electron (RE) plateau plasmas in DIII-D. Two novel methods of measuring the RE current profile in high-current RE plateaus are introduced and compared: localization of the q = 2 rational surface using visible synchrotron emission (SE) imaging and the measurement of the polarization angle of line-integrated Ar-II line emission. The two methods are found to be consistent with each other within the data uncertainties. Different simulations of the RE current profile are compared with the measurements: the toroidal fluid RE model is found to best fit the data, within the measurement uncertainties. In addition to introducing two novel methods to measure the RE current profile and validating present simulation capabilities, this work demonstrates that instabilities can grow at q = 2 and q = 1 surfaces without necessarily causing a RE final loss instability. Numerical simulations are also presented to elucidate the role of these instabilities on synchrotron emission.

Insights into the fracture properties of recycled ceramic and rubber composite cement-based materials: Fracture mechanics, acoustic emission, and digital image correlation

Recycling plays a pivotal role in construction waste management, offering a path toward sustainability for the industry. Although waste ceramics can compensate for the mechanical properties of rubberized cement-based materials, the smooth glaze surface of waste ceramics increases the risk of brittle failure. This study investigated the effect of ceramic waste aggregate (CWA) on the fracture properties of rubberized mortar through the three-point bending experiment. The fracture parameters were calculated using the Double-K fracture criterion. Simultaneously, acoustic emission (AE) and digital image correlation (DIC) technologies were used to explore the fracture damage mechanism and the crack evolution process. The results indicate that the integration of 15 % and 45 % CWA significantly enhances both initiation (KICini) and unstable (KICun) fracture toughness, whereas incorporating 90 % CWA leads to a 16.8 % and 8.2 % decrease in (KICini)and (KICun), respectively. The fracture energy (GF) of rubberized mortar exhibits a continuous decline as a function of increasing CWA substitution rates. Furthermore, GMM-based RA-AF analysis elucidates a positive correlation between CWA content and tensile crack proportion in specimens. When the CWA content reaches 90 %, the proportion of tensile cracks is quantified at 29.83 %, surpassing that in standard mortar. Crack tip opening displacement (CTOD) at 0.5post-Pmax for specimens with 15 %, 45 %, and 90 % CWA substitution reveal improvements of 49.1 % and 17.2 %, and a decrease of 23.3 %, respectively, compared to standard mortar, indicating that 15 % and 45 % CWA effectively preserve the ductility of rubberized mortar. Elevated CWA substitution leads to an amplified strain localization phenomenon around the crack tip, heightening the propensity for brittle failure.

Transverse cracking signal characterization in CFRP laminates using modal acoustic emission and digital image correlation techniques

The process of formation and subsequent propagation of transverse cracks in 90° plies of carbon-fiber laminated composites was studied using modal acoustic emission approach and digital image correlation techniques. The results from modal acoustic emission approach, which included a newly developed processing tool for acoustic emission waveforms, provided information for identification and subsequent characterization or localization of signals originating from transverse cracking by analysis of the separated flexural and extensional Lamb wave modes in terms of their modal parameters. The digital image correlation method served as a verification tool of the acoustic emission data outputs in the terms of activity of significant localized events originating from the formation of the transverse crack in the 90oply. This made it possible to specify more locally the accompanying activity belonging to the formation or propagation of the magistral transverse crack. The manuscript also presents results related to the evolution of flexural/extensional wave modal parameters as the function of loading force for both [0/0/0/90]S and [90/0/0/0]S panels. It can be concluded that the detection of transverse cracks requires the need for applying a more complex acoustic emission data analysis methodology, while the standard parametric analysis, including the waveform peak frequency, is not sufficient. The presented methodology may serve as a basis for development of robust analysis tool capable of detecting the investigated phenomena.

Spectropolarimetric Radio Imaging of Faint Gyrosynchrotron Emission from a CME: A Possible Indication of the Insufficiency of Homogeneous Models

The geo-effectiveness of coronal mass ejections (CMEs) is determined primarily by their magnetic fields. Modeling of gyrosynchrotron (GS) emission is a promising remote sensing technique to measure the CME magnetic field at coronal heights. However, faint GS emission from CME flux ropes is hard to detect in the presence of bright solar emission from the solar corona. With high dynamic-range spectropolarimetric meter wavelength solar images provided by the Murchison Widefield Array, we have detected faint GS emission from a CME out to ∼8.3 R ⊙, the largest heliocentric distance reported to date. High-fidelity polarimetric calibration also allowed us to robustly detect circularly polarized emission from GS emission. For the first time in the literature, Stokes V detection has jointly been used with Stokes I spectra to constrain GS models. One expects that the inclusion of polarimetric measurement will provide tighter constraints on the GS model parameters. Instead, we found that homogeneous GS models, which have been used in all prior works, are unable to model both the total intensity and circular polarized emission simultaneously. This strongly suggests the need for using inhomogeneous GS models to robustly estimate the CME magnetic field and plasma parameters.

Assessment of the effect of embedded RFID tag on a composite laminate strength

RFID (Radio Frequency Identification) is commonly used to monitor goods along the supply chain. The feasibility of the application of a RFID tag to monitor CFRP components was demonstrated in a previous work by some of the authors. This work is aimed at evaluating how the integration of a RFID tag inside a CFRP laminate affects the quasi-static strength and the failure mode. Finite element modelling is used to design a specimen with an embedded tag, that may be representative of the tensile state of stress in a larger laminate. Tensile testing is performed both up to failure and by interrupting tests at different load levels in order to inspect the specimen by C-scan. Acoustic Emission (AE) and Digital Image Correlation (DIC) are used as additional non-destructive monitoring techniques. Some interrupted tests were selected to extract micrographic sections that illustrate damage development in the laminate. The extensive destructive and non-destructive characterization allowed to quantify the effect of embedding a RFID tag in the laminate in terms of strength decrease and failure mode.

Virtual cylindrical PET for efficient DOI image reconstruction with sub-millimetre resolution

Objective. Image reconstruction in high resolution, narrow bore PET scanners with depth of interaction (DOI) capability presents a substantial computational challenge due to the very high sampling in detector and image space. The aim of this study is to evaluate the use of a virtual cylinder in reducing the number of lines of response (LOR) for DOI-based reconstruction in high resolution PET systems while maintaining uniform sub-millimetre spatial resolution. Approach. Virtual geometry was investigated using the awake animal mousePET as a high resolution test case. Using GEANT4 Application for Tomographic Emission (GATE), we simulated the physical scanner and three virtual cylinder implementations with detector size 0.74 mm, 0.47 mm and 0.36 mm (vPET1, vPET2 and vPET3, respectively). The virtual cylinder condenses physical LORs stemming from various crystal pairs and DOI combinations, and which intersect a single virtual detector pair, into a single virtual LOR. Quantitative comparisons of the point spread function (PSF) at various positions within the field of view (FOV) were compared for reconstructions based on the vPET implementations and the physical scanner. We also assessed the impact of the anisotropic PSFs by reconstructing images of a micro Derenzo phantom. Main results. All virtual cylinder implementations achieved LOR data compression of at least 50% for DOI PET reconstruction. PSF anisotropy in radial and tangential profiles was chiefly influenced by DOI resolution and only marginally by virtual detector size. Spatial degradation introduced by virtual cylinders was most prominent in the axial profile. All virtual cylinders achieved sub-millimetre volumetric resolution across the FOV when 6-bin DOI reconstructions (3.3 mm DOI resolution) were performed. Using vPET2 with 6 DOI bins yielded nearly identical reconstructions to the non-virtual case in the transaxial plane, with an LOR compression factor of 86%. Resolution modelling significantly reduced the effects of the asymmetric PSF arising from the non-cylindrical geometry of mousePET. Significance. Narrow bore and high resolution PET scanners require detectors with DOI capability, leading to computationally demanding reconstructions due to the large number of LORs. In this study, we show that DOI PET reconstruction with 50%–86% LOR compression is possible using virtual cylinders while maintaining sub-millimetre spatial resolution throughout the FOV. The methodology and analysis can be extended to other scanners with DOI capability intended for high resolution PET imaging.

Comparative study on fracture evolution in steel fibre and bar reinforced concrete beams using acoustic emission and digital image correlation techniques

In recent decades, the demand for sustainable construction practices has increased, but raw materials such as reinforcing steel remain scarce. Therefore, steel fibres have emerged as a popular and sustainable choice in the construction industry, offering a cost-effective alternative to traditional steel bar reinforcement for both flatwork and elevated structures. The purpose of this study is therefore to compare the performance of fracture behaviour between steel fibre-reinforced concrete (SFRC) and steel bar-reinforced concrete (SBRC) beams subjected to three-point bending. The fracture process was monitored by using two non-invasive techniques: acoustic emission (AE) and digital image correlation (DIC). The damage level was identified by characterizing the parameter-based AE data such as hit rate, energy release, count, rise time, amplitude, and signal strength. DIC images were employed to visualise the crack propagation in parallel with the AE data. To further understand the fracture characteristics, the integration of 2D source localization of AE events (based on local AE fracture energies) with DIC results was investigated. The parameter-based AE results showed that SBRC beam experienced a high density of AE hits with large peak amplitude events that were accelerated during the pre-peak loading phase. The Ib-value analysis revealed that SBRC beam exhibited a higher degree of fracture magnitude during the primary crack development process than SFRC beam. Following the main cracking stage, SFRC beam demonstrated an improved post-cracking softening behavior and superior ability to arrest crack propagation compared to SBRC beam. The integration of local AE fracture energy and DIC results provided a novel approach for a better understanding of the fracture behaviour in both SFRC and SBRC beams. This study’s findings contribute to more precise monitoring of fracture evolution in SFRC and SBRC beams, ultimately improving the selection process for primary reinforcement in flatwork and elevated structures.

Upconversion-based hydrogel kit with Python-assisted analysis platform for sample-to-result detection of organophosphorus pesticide

On-site quantitative analysis of pesticide residues is crucial for monitoring environmental quality and ensuring food safety. Herein, we have developed a reliable hydrogel portable kit using NaYbF4@NaYF4: Yb, Tm upconversion nanoparticles (UCNPs) combined with MnO2 nanoflakes. This portable kit is integrated with a smartphone reader and Python-assisted analysis platform to enable sample-to-result analysis for chlorpyrifos. The novel UCNPs maximizes energy donation to MnO2 acceptor by employing 100 % of activator Yb3+ in the nucleus for NIR excitation energy collection and confining emitter Tm3+ to the surface layer to shorten energy transfer distance. Under NIR excitation, efficient quenching of upconversion blue-violet emission by MnO2 nanoflakes occurs, and the quenched emission is recovered with acetylcholinesterase-mediated reactions. This process allows for the determination of chlorpyrifos by inhibiting enzymatic activity. The UCNPs/MnO2 were embedded to fabricate a hydrogel portable kit, the blue-violet emission images captured by smartphone were converted into corresponding gray values by Python-assisted superiority chart algorithm which achieves a real-time rapid quantitative analysis of chlorpyrifos with a detection limit of 0.17 ng mL−1. At the same time, pseudo-color images were also added by Python in “one run” to distinguish images clearly. This sensor detection with Python-assisted analysis platform provides a new perspective on pesticide monitoring and broadens the application prospects in bioanalysis.

Study on Static Mechanical Properties and Numerical Simulation of Coral Aggregate Seawater Shotcrete with Reasonable Mix Proportion

This study aims to explore the static mechanical characteristics of coral aggregate seawater shotcrete (CASS) using an appropriate mix proportion. The orthogonal experiments consisting of four-factor and three-level were conducted to explore an optimal mix proportion of CASS. On a macro-scale, quasi-static compression and splitting tests of CASS with optimal mix proportion at various curing ages employed a combination of acoustic emission (AE) and digital image correlation (DIC) techniques were carried out using an electro-hydraulic servo-controlled test machine. A comparative analysis of static mechanical properties at different curing ages was conducted between the CASS and ordinary aggregate seawater shotcrete (OASS). On a micro-scale, the numerical specimens based on particle flow code (PFC) were subjected to multi-level microcracks division for quantitive analysis of the failure mechanism of specimens. The results show that the optimal mix proportion of CASS consists of 700 kg/m3 of cementitious materials content, a water–binder ratio of 0.45, a sand ratio of 60%, and a dosage of 8% for the accelerator amount. The tensile failure is the primary failure mechanism under uniaxial compression and Brazilian splitting, and the specimens will be closer to the brittle material with increased curing age. The Brazilian splitting failure caused by the arc-shaped main crack initiates from the loading points and propagates along the loading line to the center. Compared with OASS, the CASS has an approximately equal early and low later strength mainly because of the minerals’ filling or unfilling effect on coral pores. The rate of increase in CASS is swifter during the initial strength phase and decelerates during the subsequent stages of strength development. The failure in CASS is experienced primarily within the cement mortar and bonding surface between the cement mortar and aggregate.

The Optical Spectra of Hydrogen Plasma Smelting Reduction of Iron Ore: Application and Requirements

Due to the ever‐increasing demand for high‐quality steel and the need to reduce CO2 emissions, research and development of sustainable steelmaking processes have gained a lot of interest in the past decade. One of these processes is the hydrogen plasma smelting reduction (HPSR), which has proven to be a promising solution for iron ore reduction where water vapor is formed instead of CO2. However, due to the highly dynamic and sometimes unpredictable behavior of plasmas and their nonlinear interaction with the liquid oxides, the monitoring and control of the underlying processes must be improved. This article explores the usage of optical emission spectroscopy (OES) and image analysis for HPSR process monitoring at laboratory and pilot scale. The results cover the time evolution of the OES and camera data with the focus on the most interesting radiating species, such as atomic hydrogen, iron, and oxygen together with the FeO molecule. In addition, the advantages, disadvantages, and requirements of these methods for HPSR process monitoring are discussed.

Multi-domain analysis and prediction of inductively coupled plasma jet dynamics via high-speed imaging of visible light emission

Inductively coupled plasma wind tunnels are crucial for replicating hypersonic flight conditions in ground testing. Achieving the desired conditions (e.g., stagnation-point heat fluxes and enthalpies during atmospheric reentry) requires a careful selection of operating inputs, such as mass flow, gas composition, nozzle geometry, torch power, chamber pressure, and probing location along the plasma jet. The study presented herein focuses on the influence of the torch power and chamber pressure on the plasma jet dynamics within the 350 kW Plasmatron X ICP facility at the University of Illinois at Urbana-Champaign. A multi-domain analysis of the jet behavior under selected power-pressure conditions is presented in terms of emitted light measurements collected using high-speed imaging. We then use Gaussian Process Regression to develop a data-informed learning framework for predicting Plasmatron X jet profiles at unseen pressure and power test conditions. Understanding the physics behind the dynamics of high-enthalpy flows, particularly plasma jets, is the key to properly design material testing, perform diagnostics, and develop accurate simulation models.

Association between retinal microvascular abnormalities and late-life brain amyloid-β deposition: the ARIC-PET study

BackgroundRetinal microvascular signs are accessible measures of early alterations in microvascular dysregulation and have been associated with dementia; it is unclear if they are associated with AD (Alzheimer’s disease) pathogenesis as a potential mechanistic link. This study aimed to test the association of retinal microvascular abnormalities in mid and late life and late life cerebral amyloid.MethodsParticipants from the ARIC‐PET (Atherosclerosis Risk in Communities‐Positron Emission Tomography) study with a valid retinal measure (N = 285) were included. The associations of mid- and late-life retinal signs with late-life amyloid-β (Aβ) by florbetapir PET were tested. Two different measures of Aβ burden were included: (1) elevated amyloid (SUVR > 1.2) and (2) continuous amyloid SUVR. The retinal measures’ association with Aβ burden was assessed using logistic and robust linear regression models. A newly created retinal score, incorporating multiple markers of retinal abnormalities, was also evaluated in association with greater Aβ burden.ResultsRetinopathy in midlife (OR (95% CI) = 0.36 (0.08, 1.40)) was not significantly associated with elevated amyloid burden. In late life, retinopathy was associated with increased continuous amyloid standardized value uptake ratio (SUVR) (β (95%CI) = 0.16 (0.02, 0.32)) but not elevated amyloid burden (OR (95%CI) = 2.37 (0.66, 9.88)) when accounting for demographic, genetic and clinical risk factors. A high retinal score in late life, indicating a higher burden of retinal abnormalities, was also significantly associated with increased continuous amyloid SUVR (β (95% CI) = 0.16 (0.04, 0.32)) independent of vascular risk factors.ConclusionsRetinopathy in late life may be an easily obtainable marker to help evaluate the mechanistic vascular pathway between retinal measures and dementia, perhaps acting via AD pathogenesis. Well-powered future studies with a greater number of retinal features and other microvascular signs are needed to test these findings.

Laboratory visualization of damage asymmetry formation of rock fracture via acoustic emission and digital imaging correlation

Rock fracture mechanics and accurate characterization of rock fracture are crucial for understanding a variety of phenomena interested in geological engineering and geoscience. These phenomena range from very large-scale asymmetrical fault structures to the scale of engineering projects and laboratory-scale rock fracture tests. Comprehensive study can involve mechanical modeling, site or post-mortem investigations, and inspection on the point cloud of the source locations in the form of earthquake, micro-seismicity, or acoustic emission. This study presents a comprehensive data analysis on characterizing the forming of the asymmetrical damage zone around a laboratory mixed-mode rock fracture. We substantiate the presence of asymmetrical damage through qualitative analysis and demonstrate that measurement uncertainties cannot solely explain the observed asymmetry. The implications of this demonstration can be manifold. On a larger scale, it solidifies a mechanical model used for explaining the contribution of aseismic mechanisms to asymmetrical fault structures. On a laboratory scale, it exemplifies an alternative approach to understanding the observational difference between the source location and the in situ or post-mortem inspection on the rock fracture path. The mechanical model and the data analysis can be informative to the interpretations of other engineering practices as well, but may face different types of challenges.

Whole Reconstruction-Free System Design for Direct Positron Emission Imaging From Image Generation to Attenuation Correction.

Direct positron emission imaging (dPEI), which does not require a mathematical reconstruction step, is a next-generation molecular imaging modality. To maximize the practical applicability of the dPEI system to clinical practice, we introduce a novel reconstruction-free image-formation method called direct μCompton imaging, which directly localizes the interaction position of Compton scattering from the annihilation photons in a three-dimensional space by utilizing the same compact geometry as that for dPEI, involving ultrafast time-of-flight radiation detectors. This unique imaging method not only provides the anatomical information about an object but can also be applied to attenuation correction of dPEI images. Evaluations through Monte Carlo simulation showed that functional and anatomical hybrid images can be acquired using this multimodal imaging system. By fusing the images, it is possible to simultaneously access various object data, which ensures the synergistic effect of the two imaging methodologies. In addition, attenuation correction improves the quantification of dPEI images. The realization of the whole reconstruction-free imaging system from image generation to quantitative correction provides a new perspective in molecular imaging.