Global Deformation Research Articles

Digital shearography for NDT: Study on a novel experiment based method for removing global deformation✰

Fringe patterns are typically produced as the results of traditional optical Nondestructive Evaluation (NDE) employing digital shearography. Structural flaws affect the response of the surrounding material to a certain loading, resulting in unique fringe patterns that are related to the local deformation. Smaller defect information, however, can be easily lost in the fringe pattern caused by global deformation during the flaw detection procedure. In order to improve the flaw detection capabilities of this technology, it is important to streamline the inspection process and to simplify the interpretation of the results. This study proposes a practical and effective methodology that experimentally removes fringe patterns caused by global deformation in digital shearography and only retains the defect information. For shearographic Non-Destructive Testing (NDT), two sets (3 or 4 images) of temporal phase-shifted interferograms under different loads P1 and P2 are recorded. This novel approach involves recording one additional set of temporal phase-shifted interferograms at a load between P1 and P2, e.g. P1’. Two phase maps of shearograms can be generated using the phase shift technique, corresponding to the two loads Δ2 = (P1’-P1) and Δ1 = (P2-P1), respectively. Because of the nondestructive nature of the testing, the magnitude of the loads P1 and P2 is small, and the 1st derivative of global deformation in the shearing direction of the test part is assumed to be linear. Therefore, a linear coefficient C based on the two shearograms can be determined. The information from global deformation is then removed by subtracting the shearogram generated with the small load Δ2 multiplied by the correlation coefficient C from the one obtained with the relatively large load Δ1. This technique is further improved by calculating a complete surface linear coefficient Cij, which improves the detail processing of the deformation of samples with complex geometry and mechanical properties. This technique is shown to effectively assess a wide range of structures, including aluminum specimens with prepared flaws and intricate composite laminates. The experimental findings demonstrate that the suggested technique improves the non-destructive testing capabilities of digital shearography, thereby simplifying defect detection and visualization.

Association of stress hyperglycemia ratio with left ventricular function and microvascular obstruction in patients with ST-segment elevation myocardial infarction: a 3.0 T cardiac magnetic resonance study.

Stress hyperglycemia, which is associated with poor prognosis in patients with acute myocardial infarction (AMI), can be determined using the stress hyperglycemia ratio (SHR). Impaired left ventricular function and microvascular obstruction (MVO) diagnosed using cardiac magnetic resonance (CMR) have also been proven to be linked to poor prognosis in patients with AMI and aid in risk stratification. However, there have been no studies on the correlation between fasting SHR and left ventricular function and MVO in patients with acute ST-segment elevation myocardial infarction (ASTEMI). Therefore, this study aimed to investigate the additive effect of fasting SHR on left ventricular function and global deformation in patients with ASTEMI and to explore the association between fasting SHR and MVO. Consecutive patients who underwent CMR at index admission (3-7 days) after primary percutaneous coronary intervention (PPCI) were enrolled in this study. Basic clinical, biochemical, and CMR data were obtained and compared among all patients grouped by fasting SHR tertiles: SHR1: SHR < 0.85; SHR2: 0.85 ≤ SHR < 1.01; and SHR3: SHR ≥ 1.01. Spearman's rho (r) was used to assess the relationship between fasting SHR and left ventricular function, myocardial strain, and the extent of MVO. Multivariable linear regression analysis was performed to evaluate the determinants of left ventricular function and myocardial strain impairment in all patients with AMI. Univariable and multivariable regression analyses were performed to investigate the correlation between fasting SHR and the presence and extent of MVO in patients with AMI and those with AMI and diabetes mellitus (DM). A total of 357 patients with ASTEMI were enrolled in this study. Left ventricular ejection fraction (LVEF) and left ventricular global function index (LVGFI) were significantly lower in SHR2 and SHR3 than in SHR1. Compared with SHR1 and SHR2 groups, left ventricular strain was lower in SHR3, as evidenced by global radial (GRS), global circumferential (GCS), and global longitudinal (GLS) strains. Fasting SHR were negatively correlated with LVEF, LVGFI, and GRS (r = - 0.252; r = - 0.261; and r = - 0.245; all P<0.001) and positively correlated with GCS (r = 0.221) and GLS (r = 0.249; all P <0.001). Multivariable linear regression analysis showed that fasting SHR was an independent determinant of impaired LVEF, LVGFI, GRS, and GLS. Furthermore, multivariable regression analysis after adjusting for covariates signified that fasting SHR was associated with the presence and extent of MVO in patients with AMI and those with AMI and DM. Fasting SHR in patients with ASTEMI successfully treated using PPCI is independently associated with impaired cardiac function and MVO. In patients with AMI and DM, fasting SHR is an independent determinant of the presence and extent of MVO.

Theoretical prediction model for the compressive behavior of the hybrid tube considering compression angle

AbstractThe oblique collision happening in vehicle accidents poses a huge threat to passive safety, which causes great difficulties in the design of energy absorption (EA) structures and the prediction of EA capacity due to its highly nonlinear deformation characteristics. This study aims to establish a theoretical prediction model for the compression performance of Carbon Fiber Reinforced Polymer (CFRP)/Al hybrid tube considering the loading angle. First, a high‐precision FE model was established to obtain the influence laws of tube diameter, Al thickness, and CFRP thickness on the crashworthiness of CFRP/Al hybrid tubes, laying the foundation for subsequent theoretical model validation. Second, by summarizing the deformation modes of hybrid tubes generated by various parameter combinations, a modified global origami deformation assumption was proposed under multi‐angle compression conditions, and the key terms in energy composition are extracted based on the initial and final states of folding elements. Third, a theoretical model for predicting the mean crushing forces (MCFs) of hybrid tubes was established by revealing the correlation mechanism between energy composition terms and loading angle. Finally, the theoretical prediction model was validated by experiment and simulation results and the application premise was given. Results showed that the theoretical prediction model was proved to be of high accuracy, as the average absolute prediction errors of MCF under axial, 10°, 20°, and 30° compression conditions were 6.54%, 4.63%, 3.72%, and 3.93%, respectively. This study provides valuable guidance for the forward design and development of multi‐material hybrid structures facing complex crushing conditions.Highlights An analytical model of the hybrid circular tubes considering compression angle is newly proposed. Deformation mode and axial crushing response are analyzed by experiments. The major energy dissipation mechanism for hybrid circular tubes is explicitly derived. The Al thickness has the most significant impact on energy absorption. The recommendations for the design and development of hybrid tube are provided.

FE-analytical slice model and verification test for load distribution analysis and optimization of planetary gear train in wind turbine

Load distribution behavior of planetary gear train (PGT) is crucial for the contact and bending fatigue failure of wind turbine transmission system. With the increasing power of wind turbines, the load and failure rate of wind turbine become larger, which leads to the demand of accurate and efficient modeling, analysis and optimization for load distribution of PGT. In this paper, a new efficient and accurate FE-analytical slice model for load distribution analysis and optimization of PGT in wind turbine is proposed, which is explicitly formulated by the geometry slice model of external/internal gear contact, original FE-analytical slice model for local contact deformation, and efficient finite element (FE) model for global structural deformation. In the FE-analytical slice model, geometry errors are effectively descripted by discretizing gears into a series of slices, while gear tooth contact elasticity and structural elasticity are addressed by the FE-analytical method accurately and efficiently. Upon the proposed model, the load distribution behaviors of PGT with coupling effects of elasticity and errors are revealed and optimized by tooth modification and in-phase eccentricity arrangement strategy. The load distribution tests of PGT in wind turbine are conducted, verifying the proposed FE-analytical slice model which is significant to improve the load-bearing capacity and avoid the fatigue failure of wind turbine transmission system.

An ultrawide field-of-view pinhole compound eye using hemispherical nanowire array for robot vision.

Garnering inspiration from biological compound eyes, artificial vision systems boasting a vivid range of diverse visual functional traits have come to the fore recently. However, most of these artificial systems rely on transformable electronics, which suffer from the complexity and constrained geometry of global deformation, as well as potential mismatches between optical and detector units. Here, we present a unique pinhole compound eye that combines a three-dimensionally printed honeycomb optical structure with a hemispherical, all-solid-state, high-density perovskite nanowire photodetector array. The lens-free pinhole structure can be designed and fabricated with an arbitrary layout to match the underlying image sensor. Optical simulations and imaging results matched well with each other and substantiated the key characteristics and capabilities of our system, which include an ultrawide field of view, accurate target positioning, and motion tracking function. We further demonstrate the potential of our unique compound eye for advanced robotic vision by successfully completing a moving target tracking mission.

A constitutive model for shear thickening fluid (STF) impregnated Kevlar fabric subjected to impact loading

A constitutive model is presented herein to predict the response and failure of STF impregnated Kevlar fabric under impact loading on the basis of the progressive damage model for fibre reinforced plastic (FRP) laminates. In the constitutive model, the strain rate effect of shear strength is innovatively connected with the rheological property of STF. In order to verify the validity and accuracy of the model, numerical simulations of both ballistic and low-velocity impact experiments of STF impregnated Kevlar fabric are conducted. Furthermore, parametric study is carried out on the influences of impact velocity and rheological behavior of STF. It transpires that the numerical results using the constitutive model are in good agreement with the experimental data in terms of residual velocity, load-displacement curve, energy absorption, global deformation and failure patterns. It also transpires that, with the same impact energy, STF impregnated Kevlar fabric shows stronger resistance to lower velocity ballistic impact. In addition, the maximum viscosity and shear thickening interval of the STF have a significant effect on the ballistic performance of the STF impregnated Kevlar fabric.

Numerical evaluation of impact resistance of reinforced concrete walls

Reinforced concrete(RC) structures are occasionally subjected to accidental impact during service, which can cause economic losses and casualties. Most previous research on the impact resistance of RC structures has focused on beams, columns, and slabs except walls. Thus, it is necessary to study the impact response and resistance performance of essential RC walls with high resistance requirements, such as critical shear walls, important structures, and vital protective structures of high-rise buildings in earthquake and mountainous areas under low-speed impact. This research verified the finite element model (FEM) through pendulum impact experiments on RC walls (with an impact mass of 2 tons) firstly, then proposed the damage assessment parameters of the RC wall, and analysed the impact response mechanism and resistance performance of RC walls with several reinforcement ratios under different impact loads. The research results indicate that the impact effect on the wall must consider the different value (D-value) between local and global deformation. The impact load significantly influences the peak impact force and the displacement of the RC wall. The mass affects the RC wall’s global residual deflection. At the same time, the velocity significantly influences local displacement, and correspondingly, the RC wall is more prone to local damage with high velocity. Thickness, the concrete fc, and the reinforcement ratio affect the impact resistance of the RC wall. The thicker wall can cause a shorter impact duration, and milder concrete damage, but the smaller rebar stress. The larger fc will bring greater rebar stress and milder concrete damage. A high reinforcement ratio will increase the impact force platform value and the RC wall’s concrete damaged ratio but will reduce the plastic strain of the rebars.

Experimental and numerical investigation on the impact response of bolt-ball joints

The densely populated space lattice structure requires reliable performance under impact loads. The bolt-ball joint serves a crucial role in connecting members at various angles, significantly contributing to the overall safety of the structure. However, there is limited literature available on the impact resistance of the bolt-ball joint. In this study, the drop hammer impact test system was employed to conduct impact tests on 11 specimens of bolt-ball joints. Comprehensive records were maintained, including the final deformation states, video recordings of the impact process, and data on impact force, displacement, and strain. Additionally, numerical simulation analysis was conducted to expand the scope of the study. Five failure modes were observed: global bending deformation, bolt fracture, local denting, coupling deformation of local denting and global bending deformation, bolt and tube fracture. When the impact applied at the bolt ball or conical head and steel tube welding positions, the impact process was categorized into three stages: inertia, global bending deformation, and elastic recovery/bolt fracture. When the impact position was the steel tube, coupling deformation and elastic recovery/ bolt and tube fracture were observed. The energy absorption during the impact test was analyzed, revealing a positive correlation between the degree of specimen failure and the proportion of energy absorbed relative to the work done by the impact force. The effects of impact velocity, impact position, bolt dimension and impact angle on the dynamic response of the specimens were thoroughly analyzed.

Recent collisional history of (65803) Didymos

The Double Asteroid Redirection Test (DART, NASA) spacecraft revealed that the primary of the (65803) Didymos near-Earth asteroid (NEA) binary system is not exactly the expected spinning top shape observed for other km-size asteroids. Ground based radar observations predicted that such shape was compatible with the uncertainty along the direction of the asteroid spin axis. Indeed, Didymos shows crater and landslide features, and evidence for boulder motion at low equatorial latitudes. Altogether, the primary seems to have undergone sudden structural failure in its recent history, which may even result in the formation of the secondary. The high eccentricity of Didymos sets its aphelion distance inside the inner main belt, where it spends more than 1/3 of its orbital period and it may undergo many more collisions than in the NEA region. In this work, we investigate the collisional environment of this asteroid and estimate the probability of collision with multi-size potential impactors. We analyze the possibility that such impacts produced the surface features observed on Didymos by comparing collisional intervals with estimated times for surface destabilization by the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect. We find that collisional effects dominate over potential local or global deformation due to YORP spin up.

A Coarsened-Shell-Based Cosserat Model for the Simulation of Hybrid Cables

The simulation of elastic slender objects like cables is essential for industrial applications in predicting elastic behaviors and life cycles. The Cosserat model and its variants are the dominant approaches due to their high efficiency and accuracy. However, these assume cables with homogeneous interiors and thus cannot simulate hybrid cables containing different materials. We address this by developing a novel coarsened-shell-based Cosserat (CSC) model. The CSC model constructs a material-aware elastic energy function along the cable’s cross-section to describe the global elastic behavior. The CSC model is specifically developed by carefully leveraging the strengths of three approaches: the Cosserat theory to model slender cables, the Kirchhoff–Love shell theory to model the cable’s cross-sectional energy, and numerical coarsening to reduce the degrees of freedom in the shell simulation via constructing a set of new types of material-aware shape/base functions. This allows the more accurate computation of the local and global deformations of hybrid cables, surpassing the classical Cosserat models in accuracy.

Thermal and structural analysis of the DONES target system under steady state and transient loading conditions

One of the crucial steps in the European Roadmap to the realisation of fusion energy is the design and construction of the Demo-orientated NEutron Source (DONES) facility. DONES is a fusion-like neutron source, based on the International Fusion Materials Irradiation Facility (IFMIF) concept, aimed at qualifying and testing the materials to be used in fusion reactors. The Target System (TSY) is a crucial system as it is the component where the interactions between deuterons and a liquid lithium target, flowing on a solid surface (i.e. the Back Plate), take place to produce neutrons for irradiating the testing materials. In this regard, an investigation campaign has been performed to evaluate the thermo-mechanical behaviour of the DONES TSY under selected steady state and transient loading conditions, in light of the most recent design updates (new bellows and connection systems). The first part of the assessment concerned the analysis of the TSY under the normal operation steady state loading scenario. A detailed 3D FEM model has been set up, considering the newest updates of the TSY geometry and of the operational parameters, and a thermo-mechanical analysis has been launched. Results have been mainly checked in terms of TSY global deformation, focusing on the Back Plate and on the connecting bellows displacements, in order to exclude overlapping with the High Flux Test Module and misalignments with the beam footprint. Afterwards, since the lithium inlet temperature has been increased from 250 °C to 300 °C, a transient thermo-mechanical analysis of the TSY under the start-up loading conditions has been performed to check if it is able to withstand the hotter lithium flow according to the RCC-MRx criteria. Therefore, the reference pre-heating strategy has been adopted, assessing the thermal and mechanical behaviour of the TSY, focusing on the Back Plate. The obtained results are presented and critically discussed, suggesting important recommendations for the follow-up of the design.

Worse Patient-Reported Outcomes and Spino-Pelvic Parameters After Total Hip Arthroplasty for Rapidly Progressive Osteoarthritis of the Hip Compared to Osteoarthritis: A Propensity-Matched Cohort Study

BackgroundThis study aimed to assess the association between the disease process of hip osteoarthritis and total hip arthroplasty (THA) outcomes; this is a critical issue, as rapid progression has been postulated to be responsible for patient dissatisfaction after THA. MethodsThis retrospective case-control study included 255 patients who underwent THA and completed a mean follow-up duration of 42.1 months (range, 24.0 to 77.0). We classified patients into those who had (n = 26) and did not have (n = 229) rapidly progressive osteoarthritis of the hip (RPOA), defined as a narrowing rate of joint space ≥ 2 mm yearly or a ≥ 50% loss within 12 months, excluding any other cause of a destructive arthropathy. Propensity score-matched cohorts for age, sex, body mass index, and spino-pelvic measures were created, and the outcomes were compared between the 2 groups. ResultsAfter successfully matching RPOA (n = 25) and non-RPOA patients (n = 50), there were significant differences in minimum clinically important difference (P = .009 for European Quality of Life 5-Dimension, and P < .001 for low back pain), patient acceptable symptom state (P = .015 for European Quality of Life 5-Dimension, and P < .001 for Hip Disability and Osteoarthritis Outcome Score Joint Replacement score), patient satisfaction (P = .028), and T1 pelvic angle as an indicator of global sagittal spinal deformity (P = .017). There was a correlation between T1 pelvic angle and low back pain in the RPOA group (R = 0.628, P < .001). ConclusionsPatients who exhibited RPOA before undergoing THA showed worse patient-reported outcomes compared with those who did not have rapid progression. Our study highlights the critical role of the disease process in influencing THA outcomes, advocating for a paradigm shift toward more meticulous preoperative evaluations, including global spinal deformity, standardized diagnostic criteria, and tailored interventions.

SST2 and morphofunctional parameters of the left ventricle in patients with ischemic heart disease with chronic heart failure and previous COVID-19

Objective: to assess the concentration of the sST2 biomarker and its relationship with the morphological and functional parameters of the LV myocardium in patients with coronary artery disease and chronic heart failure (CHF) l-lll functional class (FC), who had and did not have COVID-19. Material and methods. We examined 100 patients (66 males), median (Me) age 65 [63; 67] years, with stable coronary artery disease with CHF l-lll FC (New York Heart Association), divided into 2 groups depending on the COVID-19. Along with the conventional clinical examination, the concentration of serum sST2 was determined by enzyme immunoassay Results. It was found that in patients who underwent COVID-19 (group 1), the sST2 level was 38.4 [35.5; 44.8] ng/ml, in the comparison group (group 2) — 29.63 [27.9; 32.7] ng/ml (p&lt;0.001). In group 1, the final diastolic volume and the final systolic volume of LV significantly exceeded those in group 2 (p=0.004 and p=0.02) and amounted to 118.2 [107.5; 166.5] and 44.1 [35.0; 58.1] ml, respectively, for the 1st and 107.5 [92.4; 129.5] and 37.9 [29.5; 47.4] ml for the 2nd group. The number of patients with grade 2 diastolic dysfunction (DD) in group 1 (18-33.9%) significantly exceeded that in the comparison group (7-14.9%). Changes in global longitudinal deformation of LV in COVID-19 group (-15.6 [-20.8; -13.8]%) were more pronounced than in the comparison group (-19.9 [-21.5; -16.3]%)(p=0.018). Conclusion. CHD patients with CHF l-lll FC and previous COVID-19, have significantly higher serum sST2, more pronounced LV DD and greater global longitudinal deformation.

Towards the realization of composite metastructures: A failure analysis of connections

Metastructures hold significant potential for applications such as adaptive structures and soft robotics. Architectures of fiber-reinforced polymer metastructures may relate to modular arrangement of straight and curved laminates, with their connections to resemble perfect cracks, thus susceptible to delamination. This study investigated geometrical effects on the load-carrying capabilities of these connections upon a global tensile deformation, as well as lean modeling tools to facilitate the development of architected composite metastructures. Numerical fracture mechanics approach on different connection geometries and thicknesses showed that connection delamination is a critical failure mode, but crack-driving-force has low dependence on connection shape for given ligament thickness (and stiffness). Adopted analytical models could capture either moment or force-driven delamination failure, while the intermediate regime necessitates numerical tools. First-ply failure may precede depending on shape and ligament stiffness. These trends were also verified on an exemplary rotating chiral composite geometry. Furthermore, interface load-carrying capability improvements were studied via design considerations including connection filler material and element variable thickness. Indicatively, the latter showed a 157 % increase in bending deflection (and global deformations), while reducing crack driving force by 38 % for a given load case. The conducted analysis offers valuable insights into the design of lightweight, load-carrying composite metastructures.

Experimental study on the synergetic damage of sandwich panel with armored hybrid core under combined blast and fragment loading

Synergetic damage under combined blast and fragment loading drives innovational design of protective structures. In present study, sandwich panel with armored hybrid core was designed, fabricated and finally tested under combined blast and fragment loading. The failure behaviors and the underlying mechanisms were analyzed for the components of sandwich panel. The sandwich panel displayed superior performance over equivalent solid plate. The designability of special interest was exploited by elaborating the effects of face sheet configuration, core material and core sequence on the failure behaviors. Experimental results demonstrate that the same thickness of the front and back faces is beneficial for the constraint of back face deflection. The aluminum foam and ultra-high molecular weight polyethylene (UHMWPE) laminate, adopted as the components of armored hybrid core, cooperated well against combined blast and fragment loading by suffering crushing erosion failure and global bulge deformation, respectively. The potential of armored hybrid core is strongly associated with the core sequence. The ceramic layer supported by the material with high stiffness and the protection of upper bulletproof material for UHMWPE laminate layer would benefit the performance of whole panel. The optimal design of core sequence could markedly reduce back face deflection and even avoid the petalling failure of back face.

Mechanical behavior of interpenetrating phase composite structures based on triply periodic minimal surface lattices

The triple periodic minimal surface (TPMS) structures have received widespread attention due to their excellent mechanical properties, such as high specific strength and energy absorption. However, these structures are prone to suffering catastrophic damage due to stress concentration and shear deformation in actual loading environments, affecting their load-bearing performance. In this work, interpenetrating phase composite (IPC) structures were fabricated by filling thermoplastic polyurethane (TPU) as a soft material into the diamond minimal surface structure using the multi-material fused deposition modeling technique, and their mechanical behavior was investigated numerically and experimentally. The effects of topological types and volume fractions on the performance of IPC structures were investigated. It is shown that the IPC structure undergoes stretching-dominated deformation, and its strength and toughness are significantly improved compared to the TPMS structure. Due to the addition of a complementary phase structure made of TPU, stress concentration and shear failure are reduced. The global deformation of the IPC structure and stress distribution of the TPMS phase are more uniform, effectively protecting the entire structure from catastrophic failure.

Crystal plasticity approach for predicting mechanical responses in wire-arc directed energy deposition of NbZr1 refractory alloy

The refractory alloy, such as Niobium-1 wt% Zirconium (NbZr1) alloy, is a promising candidate for diverse applications in extreme environments. This study investigates an integrated experimental and computational methodology that can predict the mechanical properties of wire-arc directed energy deposited (DED) refractory NbZr1 alloy. The effect of large columnar grains with strong texture induced by the wire-DED process has been successfully incorporated into the representative volume element (RVE). Performing crystal plasticity (CP) simulation on RVE of NbZr1, deformation behavior and stress-strain relationship are predicted to explore the process-structure-property (PSP) relationship. The RVE has been created in synthetic microstructure generation software utilizing the grain statistics derived from electron backscatter diffraction (EBSD) analysis, capturing essential microstructural features. A phenomenological constitutive model and appropriate boundary conditions have been applied and solved, using the CP fast Fourier transform method. The CP model has been calibrated and validated utilizing the tensile test data along the build direction and deposition direction, respectively. The error in predicting yield strength and ultimate tensile strength is 0.91% and 0.67%, respectively, for the calibration simulation, whereas these values are 2.51% and 1.81% for the validation simulation. The results suggest strong agreement between the simulation and experimental observation. Even though global deformation behavior remains consistent across multiple RVEs with the same microstructural features, local stress-strain values vary, indicating structural anisotropy, which is also consistent with the digital image correlation (DIC) result. It is proven that this proposed CP method can effectively predict the mechanical responses of components with large grains and strong textures resulting from the wire-arc DED.

Physical properties of asteroid Dimorphos as derived from the DART impact

AbstractOn 26 September 2022, NASA’s Double Asteroid Redirection Test (DART) mission successfully impacted Dimorphos, the natural satellite of the binary near-Earth asteroid (65803) Didymos. Numerical simulations of the impact provide a means to find the surface material properties and structures of the target that are consistent with the observed momentum deflection efficiency, ejecta cone geometry and ejected mass. Our simulation that best matches the observations indicates that Dimorphos is weak, with a cohesive strength of less than a few pascals, like asteroids (162173) Ryugu and (101955) Bennu. We find that the bulk density of Dimorphos ρB is lower than ~2,400 kg m−3 and that it has a low volume fraction of boulders (≲40 vol%) on the surface and in the shallow subsurface, which are consistent with data measured by the DART experiment. These findings suggest that Dimorphos is a rubble pile that might have formed through rotational mass shedding and reaccumulation from Didymos. Our simulations indicate that the DART impact caused global deformation and resurfacing of Dimorphos. ESA’s upcoming Hera mission may find a reshaped asteroid rather than a well-defined crater.

Machine learning clustering of adult spinal deformity patients identifies four prognostic phenotypes: a multicenter prospective cohort analysis with single surgeon external validation

BACKGROUND CONTEXTAmong adult spinal deformity (ASD) patients, heterogeneity in patient pathology, surgical expectations, baseline impairments, and frailty complicates comparisons in clinical outcomes and research. This study aims to qualitatively segment ASD patients using machine learning-based clustering on a large, multicenter, prospectively gathered ASD cohort. PURPOSETo qualitatively segment adult spinal deformity patients using machine learning-based clustering on a large, multicenter, prospectively gathered cohort. STUDY DESIGN/SETTINGMachine learning algorithm using patients from a prospective multicenter study and a validation cohort from a retrospective single center, single surgeon cohort with complete 2-year follow up. PATIENT SAMPLEAbout 805 ASD patients; 563 patients from a prospective multicenter study and 242 from a single center to be used as a validation cohort. OUTCOME MEASURESTo validate and extend the Ames-ISSG/ESSG classification using machine learning-based clustering analysis on a large, complex, multicenter, prospectively gathered ASD cohort. METHODSWe analyzed a training cohort of 563 ASD patients from a prospective multicenter study and a validation cohort of 242 ASD patients from a retrospective single center/surgeon cohort with complete two-year patient-reported outcomes (PROs) and clinical/radiographic follow-up. Using k-means clustering, a machine learning algorithm, we clustered patients based on baseline PROs, Edmonton frailty, age, surgical history, and overall health. Baseline differences in clusters identified using the training cohort were assessed using Chi-Squared and ANOVA with pairwise comparisons. To evaluate the classification system's ability to discern postoperative trajectories, a second machine learning algorithm assigned the single-center/surgeon patients to the same 4 clusters, and we compared the clusters' two-year PROs and clinical outcomes. RESULTSK-means clustering revealed four distinct phenotypes from the multicenter training cohort based on age, frailty, and mental health: Old/Frail/Content (OFC, 27.7%), Old/Frail/Distressed (OFD, 33.2%), Old/Resilient/Content (ORC, 27.2%), and Young/Resilient/Content (YRC, 11.9%). OFC and OFD clusters had the highest frailty scores (OFC: 3.76, OFD: 4.72) and a higher proportion of patients with prior thoracolumbar fusion (OFC: 47.4%, OFD: 49.2%). ORC and YRC clusters exhibited lower frailty scores and fewest patients with prior thoracolumbar procedures (ORC: 2.10, 36.6%; YRC: 0.84, 19.4%). OFC had 69.9% of patients with global sagittal deformity and the highest T1PA (29.0), while YRC had 70.2% exhibiting coronal deformity, the highest mean coronal Cobb Angle (54.0), and the lowest T1PA (11.9). OFD and ORC had similar alignment phenotypes with intermediate values for Coronal Cobb Angle (OFD: 33.7; ORC: 40.0) and T1PA (OFD: 24.9; ORC: 24.6) between OFC (worst sagittal alignment) and YRC (worst coronal alignment). In the single surgeon validation cohort, the OFC cluster experienced the greatest increase in SRS Function scores (1.34 points, 95%CI 1.01–1.67) compared to OFD (0.5 points, 95%CI 0.245–0.755), ORC (0.7 points, 95%CI 0.415–0.985), and YRC (0.24 points, 95%CI -0.024–0.504) clusters. OFD cluster patients improved the least over 2 years. Multivariable Cox regression analysis demonstrated that the OFD cohort had significantly worse reoperation outcomes compared to other clusters (HR: 3.303, 95%CI: 1.085–8.390). CONCLUSIONMachine-learning clustering found four different ASD patient qualitative phenotypes, defined by their age, frailty, physical functioning, and mental health upon presentation, which primarily determines their ability to improve their PROs following surgery. This reaffirms that these qualitative measures must be assessed in addition to the radiographic variables when counseling ASD patients regarding their expected surgical outcomes.

Lateral junctions of transition metal dichalcogenides as ballistic channels for straintronic applications

In the context of advanced nanoelectronics, two-dimensional semiconductors such as transition metal dichalcogenides (TMDs) are gaining considerable interest due to their ultimate thinness, clean surface and high carrier mobility. The engineering prospects offered by those materials are further enlarged by the recent realization of atomically sharp TMD-based lateral junctions, whose electronic properties are governed by strain effects arising from the constituents lattice mismatch. Although most theoretical studies considered only misfit strain, first-principles simulations are employed here to investigate the transport properties under external deformation of a three-terminal device constructed from a MoS2/WSe2/MoS2 junction. Large modulation of the current is reported owing to the change in band offset, illustrating the importance of strain on the p–n junction characteristics. The device operation is demonstrated for both local and global deformations, even for ultra-short channels, suggesting potential applications for ultra-thin body straintronics.