Intact State Research Articles

Potential for 50% Mechanical Strength Decline in Sandstone Reservoirs Due to Salt Precipitation and CO2–Brine Interactions During Carbon Sequestration

AbstractPredictive modeling of CO2 storage sites requires a detailed understanding of physico-chemical processes and scale-up challenges. Dramatic injectivity decline may occur due to salt precipitation pore clogging in high-salinity aquifers during subsurface CO2 injection. This study aims to elucidate the impact of CO2-induced salt crystallization in the porous medium on the geomechanical properties of reservoir sandstones. As the impact of salt precipitation cannot be isolated from the precursor interactions with CO2 and acidified brine, we present a comprehensive review and discuss CO2 chemo-mechanical interactions with sandstones. Laboratory geochemical CO2–brine–rock interactions at elevated pressures and temperatures were conducted on two sandstone sets with contrasting petrophysical qualities. Interaction paths comprised treatment with (a) CO2-acidified brine and (b) supercritical injection until brine dry-out, salt crystallization, and growth. Afterward, the core samples were tested in a triaxial apparatus at varying stresses and temperatures. The elastic moduli of intact, CO2-acidified brine treated, and salt-affected sandstones were juxtaposed to elucidate the geochemical–geomechanical-coupled impacts and identify the extent of crystallization damages. The salt-affected sandstones showed a maximum of 50% reduction in Young’s and shear moduli and twice an increase in Poisson’s ratio compared to intact condition. The deterioration was notably higher for the tighter reservoir sandstones, with higher initial stiffness and lower porosity–permeability. We propose two pore- and grain-scale mechanisms to explain how salt crystallization contributes to stress localization and mechanical damage. The results highlight the potential integrity risk imposed by salt crystallization in (hyper)saline aquifers besides injectivity, signaling mechanical failure exacerbated by pressure buildup.

Conventional one-handed compared to two-handed endoscopic ear surgery using an endoscope holder: a single center study.

One-handedness is a challenge in conventional endoscopic ear surgery (EES). We present results on the first-ever application of the passive endoscope holder 'Endofix exo' (Co. AKTORmed GmbH, Neutraubling, Germany) in EES, which enables two-handed surgery. This two-sided study compares cut-suture time, operating time, postoperative complications, graft take rates, hearing results and quality of life in patients who underwent first stage tympanoplasty due to tympanic membrane perforation with intact ossicular chain conditions. 25 patients received classic EES (EES-, mean age: 28 ± 21 years) and 15 received EES with the passive holder (EES+, mean age: 48 ± 21 years). Mean operating times (EES-: 96 ± 38 (SD) min; EES+: 107 ± 33min), cut-suture times (EES-: 68 ± 30min; EES+: 73 ± 31min), complications, graft take rates and hearing results (preoperative air bone gap (ABG) (PTA4): 15 dB ± SD 8 dB (EES-); 16 dB ± SD 8 dB (EES+); postoperative ABG (PTA4): 11.25dB ± SD 11.3dB (EES-); 14 dB ± SD 10 dB (EES+)) did not differ significantly (p > 0.05) between the two groups. Postoperative hearing results and quality of life tended to improve in both groups (p > 0.05). The passive endoscope holder has been successfully applied during the course of the study. However, modifications of the endoscope holder and further studies are recommended focusing on positioning of grafts and prostheses to obtain conclusive results regarding the superiority of two-handed EES over one-handed conventional EES.

Anterior and coracoid base tunnel location combined with single -or double clavicular tunnel techniques using double-button fixation for coracoclavicular ligament reconstruction both restore horizontal stability. A biomechanical cadaver study

BackgroundThe placement of clavicle tunnels in coracoclavicular ligament reconstruction is well established, but the optimal position of the coracoid tunnel remains unclear. This study aimed to investigate how the coracoid tunnel's position affects horizontal stability during coracoclavicular ligament reconstruction using a double-button technique. MethodsFifteen fresh frozen shoulder cadaver specimens were tested under various conditions: intact coracoclavicular ligaments, disrupted ligaments, and reconstructions with a single coracoid and clavicle tunnel or double clavicle tunnels. The coracoid tunnel was positioned at the coracoid base 1/9, and 1/5 anterior to the base. Specimens underwent displacement-controlled loading, with 2D motion analysis conducted on captured digital images using TEMA motion analysis. FindingsMean displacement for intact coracoclavicular ligaments was 1.61 ± 0.92 mm, and 3.69 ± 1.09 mm for disrupted ligaments. For reconstructed conditions, displacements were as follows: Single-Tunnel Base (1.87 ± 0.64 mm), Single-Tunnel 1/9 (2.54 ± 1.13 mm), Single-Tunnel 1/5 (2.62 ± 1.17 mm), Double-Tunnel Base (1.25 ± 0.73 mm), Double-Tunnel 1/9 (2.03 ± 1.22 mm), and Double-Tunnel 1/5 (1.88 ± 1.20 mm). Differences among intact, reconstructed, and disrupted states were statistically significant (p = 0.01–0.0001), with all reconstruction techniques restoring horizontal displacement near the intact state. InterpretationAt point zero both single coracoid tunnel and single- and double-clavicle tunnel restored horizontal displacement to its intact state. Coracoid tunnel placement anterior to the base of the coracoid did not influence horizontal displacement but single coracoid at the coracoid base and single clavicle tunnel resulted in the most anatomic reconstruction. Single coracoid tunnel at the base and double-clavicle resulted in the most stable reconstruction.

Assessing the consistency and sensitivity of the neural correlates of narrative stimuli using functional near-infrared spectroscopy

Abstract Investigating how the brain responds to rich and complex narratives, such as engaging movies, has helped researchers study higher-order cognition in 'real-world' scenarios. These neural correlates are particularly useful in populations where behavioural evidence of cognition alone is inadequate, such as children and certain patient populations. While this research has been primarily conducted in fMRI and EEG, whether functional near-infrared spectroscopy (fNIRS) can reliably detect these neural correlates at an individual level, which is required for effective use in these populations, has yet to be established. This study replicated widespread inter-subject correlations (ISCs) in the frontal, parietal and temporal cortices in fNIRS in healthy participants when they watched part of the TV episode Bang! You're Dead and listened to an audio clip from the movie Taken. Conversely, these ISCs were primarily restricted to temporal cortices when participants viewed scrambled versions of those clips. To assess whether these results were reliable at the single-participant level, two follow-up analyses were conducted. First, the consistency analysis compared each participant's ISCs against group results that excluded that individual. This approach found that 24/26 participants in Bang! You're Dead and 20/26 participants in Taken were statistically similar to the group. Second, the sensitivity analysis measured whether machine learning algorithms could decode between intact conditions and their scrambled counterparts. This approach yielded balanced accuracy scores of 81% in Bang! You're Dead and 79% in Taken. Overall, the neural correlates of narrative stimuli, as assessed by fNIRS, are reproducible across participants, supporting its broad application to clinical and developmental populations.

Should individuals with unilateral transtibial amputation carry a load on their intact or prosthetic side?

Carrying side loads often occurs during activities of daily living. As walking is most unstable mediolaterally, side load carriage may further compromise gait biomechanics, especially for transtibial amputees (TTAs). This study investigated the effects of side load carriage on gait kinetics during steady-state walking to determine which side, intact or prosthetic, TTAs should carry a load. Twelve unilateral TTAs wore a passive-elastic foot and carried a side load of 13.6 kg while walking at their self-selected speed. Kinetic metrics, including ground reaction force peaks and impulses, loading and unloading rates, and joint moments and powers, were analyzed. TTAs had smaller propulsive forces on their intact limb during the prosthetic side load condition. During the intact side load condition, they exhibited smaller hip flexor moment in late stance and smaller knee flexor moment at the end of swing on their intact limb. They had higher hip and knee abductor moments on their intact limb and prosthetic limb in early and late stance during the contralateral side load condition. TTAs generated higher hip extensor power at weight acceptance during the ipsilateral side load. Significant interactions were observed in hip extensor power and abductor moment, suggesting strong associations between hip extensor power generation and the ipsilateral side load and between hip abductor moment and the contralateral side load. These mixed results demonstrate some kinetic changes due to side load carriage and suggest that the side TTAs should carry a load depends on the desired effects, primarily on their intact limb.

Posterior Glenoid Bone Grafting in the Setting of Excessive Glenoid Retroversion Does Not Provide Adequate Stability in a Cadaveric Posterior Instability Model

Background: Excessive glenoid retroversion is a known risk factor for posterior shoulder instability and failure after soft tissue stabilization procedures. Whether excessive glenoid retroversion is a risk factor for failure after posterior glenoid bone grafting is unknown. Purpose: To evaluate the biomechanical effectiveness of posterior iliac crest bone grafting (ICBG) for posterior shoulder instability with increasing glenoid retroversion. Study Design: Controlled laboratory study. Methods: Six fresh-frozen cadaveric shoulders had a posterior glenoid osteotomy allowing the glenoid retroversion to be set at 0°, 10°, and 20°. At these 3 preset angles, 4 conditions were simulated consecutively on the same specimen: (1) intact glenohumeral joint, (2) posterior Bankart lesion, (3) 20% posterior glenoid bone defect, and (4) posterior ICBG. Stability was evaluated in the jerk position (60° of glenohumeral anteflexion, 60° of internal rotation) by measuring (A) posterior humeral head (HH) translation (in mm) and (B) peak translational force (in N) necessary for translation of the HH over 25% of glenoid width. Results: At 0° of retroversion, the ICBG restored posterior HH translation and peak translational force to values comparable with those of the intact condition (P = .649 and P = .979, respectively). At 10° of retroversion, the ICBG restored the peak translational force to a value comparable with that of the intact condition (22.3 vs 24.7 N, respectively; P = .418) but showed a significant difference in posterior HH translation in comparison to the intact condition (4.5 vs 2.0 mm, respectively; P = .026). There was a significant increase in posterior HH translation and significant decrease in peak translational force with the ICBG at 20° of glenoid retroversion compared with the intact condition (posterior HH translation: 7.9 vs 2.0 mm, respectively; P < .006; peak translational force: 15.3 vs 24.7 N, respectively; P = .014). Conclusion: In this cadaveric study, posterior ICBG was able to restore stability to a level comparable to that of the native condition at 0° and to some extent at 10° of retroversion. However, posterior ICBG was not able to provide adequate stability at 20° of glenoid retroversion. Clinical Relevance: Posterior glenoid bone grafting with ICBG should be used with caution when performed in isolation in the setting of posterior instability associated with glenoid bone loss and combined glenoid retroversion of >10°.

Rehabilitation and reinforcement of cracked pavements using crack sealers and composite patches

Cracking is a significant concern for pavements and should be appropriately treated during road, highway, and runway rehabilitation. This study investigates the behavior of asphaltic materials under tensile and shear loading modes in intact, fractured, and repaired conditions. With this aim, several methods and materials are utilized for repairs, such as poring adhesive into the crack (using bitumen, neat epoxy resin, and polymer concrete adhesives) and patching the crack with textile (by glass fiber and epoxy resin or bitumen). These tests were conducted at +10 °C, with a three-point bending loading configuration, the same as the actual loading configuration of pavements. Criteria such as failure load, failure work, and post-failure work, as well as failure patterns, were assessed to assess the effectiveness of repairs. Numerical analysis was also performed, and a constitutive model was presented. The ultimate tensile capacity of the cracked specimen is measured at 63 % lower than the intact condition (778 N). The ultimate tensile load of the bitumen-repaired specimen is higher than that of the cracked specimen, but it is still 11 % lower than that of the intact condition. The ultimate tensile capacity of epoxy resin repaired and polymer concrete repaired specimens are 88 % and 79 % higher than the intact specimen (about 1400 N). The ultimate tensile load of the fabric patch reinforced specimen that used bitumen as the adhesive is 38 % higher than the intact specimen (1075 N), while for the case of using the epoxy resin adhesive, this value is 258 % (2788 N). Observations of tensile failure patterns show that, because bitumen is viscoelastic, failure in bitumen-repaired specimens happens in bitumen necking mode and starts at the repaired crack tip. In other cases, the failure occurred far from the pre-crack plane.

Arthroscopic Centralization of the Medial Meniscus Reduces Load on a Posterior Root Repair Under Dynamic Varus Loading: A Biomechanical Investigation

Background: In addition to the integrity of the meniscal hoop function, both the anterior and posterior meniscus roots as well as the meniscotibial and meniscofemoral ligaments are crucial in restraining meniscal extrusion. However, the interaction and load sharing between the roots and these peripheral attachments (PAs) are not known. Purposes: To investigate the influence of an insufficiency of the PAs on the forces acting on a posterior medial meniscus root repair (PMMRR) in both neutral and varus alignment and to explore whether meniscal centralization reduces these forces. Study Design: Controlled laboratory study. Methods: In 8 fresh-frozen human cadaveric knees, an arthroscopic transosseous root repair (step 1) was performed after sectioning the posterior root of the medial meniscus. The pull-out suture was connected to a load cell to allow measurement of the forces acting on the root repair. A medial closing-wedge distal femoral osteotomy was performed to change the mechanical axis from neutral to 5° of varus alignment. The meniscus was completely released from its PAs (step 2), followed by transosseous arthroscopic centralization (step 3). Each step was tested in both neutral and varus alignment. The specimens were subjected to nondestructive dynamic varus loading under axial compression of 300 N in 0°, 15°, 30°, 45°, and 60° flexion. The changes in force acting on the PMMRR were statistically analyzed using a mixed linear model. Results: Axial loading in neutral alignment led to an increase of the force of root repair of 3.1 ± 3.1 N (in 0° flexion) to 6.3 ± 4.4 N (in 60° flexion). In varus alignment, forces increased significantly from 30° (3.5 N; 95% CI, 1.1-5.8 N; P = .01) to 60° (7.1 N; 95% CI, 2.7-11.5 N; P = .007) flexion, in comparison with neutral alignment. Cutting of the PAs in neutral alignment led to a significant increase of root repair forces in all flexion angles, from 7.0 N (95% CI, 1.0-13.0 N; P = .02) to 9.1 N (95% CI, 4.1-14.1 N; P = .003), in comparison with the intact state. Varus alignment significantly increased the forces in the cut states from 4.8 N (95% CI, 1.0-8.5 N; P = .02) to 11.1 N (95% CI, 4.2-18.0 N; P = .006) from 30° to 60° flexion, in comparison with the neutral alignment. Arthroscopic centralization led to restoration of the native forces in both neutral and varus alignment, with no significant differences between the centralized and intact states. Conclusion: An insufficiency of the PAs of the medial meniscus, as well as varus alignment, led to increased forces acting on a PMMRR. These forces were reduced via an arthroscopic meniscal centralization. Clinical Relevance: Performing arthroscopic meniscal centralization concomitantly with PMMRR may reduce failure of the repair by reducing the load of the root.

Combined PCL instabilities cannot be identified using posterior stress radiographs in external or internal rotation: A cadaveric study.

Posterior stress radiography is recommended to identify isolated or combined posterior cruciate ligament (PCL) deficiencies. The posterior drawer in internal (IR) or external rotation (ER) helps to differentiate between these combined instabilities. The purpose of this study was to evaluate posterior stress radiography (PSR) in isolated and combined PCL deficiency with IR and ER compared to PSR in neutral rotation (NR) for diagnosing combined PCL instabilities. Six paired fresh-frozen human cadaveric legs (n = 12) were mounted in a Telos device for PSR. The tibia was rotated using an attached foot apparatus capable of rotating the foot 30° internally and externally. A posterior tibial load of 15 kp (147.1 N) was applied to the tibial tubercle at 90° knee flexion, and a lateral radiograph was obtained. This was repeated with the foot in 30° IR and ER. The PCL, posterolateral complex (PLC), and posteromedial complex (PMC) were sectioned in six knees, while the PMC was sectioned before the PLC in the other six knees. Posterior tibial displacement (PTD) was measured radiographically. Statistical analysis was performed using a two-way ANOVA and a mixed model with Bonferroni correction, and the significance was set at p < 0.05. Furthermore, intra- and interobserver reliability was determined. Cutting the PCL significantly increased the radiographic PTD by 9.8 ± 1.8 mm (side-to-side difference compared to the intact state of the knee, n = 12; p < 0.001). This further increased to 12.2 ± 2.3 mm (n = 6; p < 0.01) with an additional PLC deficiency and to 15.4 ± 3.4 mm (n = 6; p < 0.05) with an additional PMC deficiency. A combined PLC and PMC deficiency resulted in an increase of the PTD to 15.9 ± 4.5 mm (n = 12; p < 0.01). In the PCL/PLC deficient state, ER did not demonstrate a higher PTD, compared to the NR and IR posterior drawer. In the PCL/PMC deficient state in IR, PTD was 1.6 ± 0.7 mm (p < 0.01) higher compared to NR and 3.2 ± 1.9 mm (p < 0.05) higher compared to ER. We showed excellent intra- and interobserver reliability (0.987-0.997). Combined PCL instabilities resulted in a significant increase in posterior tibial displacement in posterior stress radiographs. However, PSR in IR or ER was unable to differentiate between these combined instabilities. Based on our data, additional stress radiographs in rotation are unlikely to provide any diagnostic benefit in the clinical setting. There is no level of evidence as this study was an experimental laboratory study.

Refined analysis of a supporting column assembly in a traditional Tibetan timber building and its limiting tilt angle before collapse

Traditional Tibetan architecture is an important part of the Chinese architecture. Many of the Tibetan structures are suffering from different types of damages after hundreds of years of service. The structural arrangement, types of damage and failure modes of these timber structures have been investigated on site. Tilting of structural members is found to be the most common type of damage. This paper studies the limiting inclination angle of a single-column supporting assembly of these structures before its collapse for proactive maintenance and restoration. A method to estimate the limiting tilt angle of the column is proposed based on the relationship between the lateral force, F, at the column head and the tilt angle, θ, of the column. Simplified analytical models of this column assembly in a traditional Tibetan timber building under in-plane and out-of-plane loadings respectively are proposed. The behavior of the constituting column foot joint, column-Queti joint and Queti-beam joint are analyzed in detail to obtain the global deformation and M-θ relationship of the column assembly under different loads. The F-θ relationship of the column assembly from the intact state to collapse is then obtained. A verified finite element model of the column assembly is adopted as reference to validate the performances of the proposed models throughout the loading process. Comparison of the F-θ curves obtained from the analytical models and the simulated results demonstrates the validity and accuracy of the proposed models. They may be adopted for a quick analysis of practical structures to estimate their limit states for health monitoring, maintenance and strengthening of structures.

Damming of streams due to the construction of a highway in the Amazon rainforest favors individual trophic specialization in the fish (Bryconops giacopinii).

In Amazonian streams, damming caused by road construction changes the system's hydrological dynamics and biological communities. We tested whether the degree of specialization in fish (Bryconops giacopinii) individuals is higher in pristine stream environments with intact ecological conditions than in streams dammed due to the construction of a highway in the Amazon rainforest. To achieve this, stomach content data and stable isotopes (δ13C and δ15N) in tissues with varying isotopic incorporation rates (liver, muscle, and caudal fin) were used to assess the variation in consumption of different prey over time. The indices within-individual component (WIC)/total niche width (TNW) and individual specialization were employed to compare the degree of individual specialization between pristine and dammed streams. The condition factor and stomach repletion of sampled individuals were used to infer the intensity of intraspecific competition in the investigated streams. The species B. giacopinii, typically considered a trophic generalist, has been shown to be, in fact, a heterogeneous collection of specialist and generalist individuals. Contrary to our expectations, a higher degree of individual specialization was detected in streams dammed by the highway. In dammed streams, where intraspecific competition was more intense, individuals with narrower niches exhibited poorer body conditions than those with broader niches. This suggests that individuals adopting more restricted diets may have lower fitness, indicating that individual specialization may not necessarily be beneficial for individuals. Our results support the notion that intraspecific competition is an important mechanism underlying individual specialization in natural populations. Our results suggest that environmental characteristics (e.g., resource breadth and predictability) and competition for food resources interact in complex ways to determine the degree of individual specialization in natural populations.

Evaluation of Tibiofemoral Contact Mechanics After a Novel Hybrid Procedure for Femoral Osteochondral Defect Repairs With a Subchondral Implant and Dermal Matrix.

There is a lack of procedures that adequately address the subchondral bone structure and function for reconstructing osteochondral defects in the femoral condyles. To biomechanically evaluate the tibiofemoral joint contact characteristics before and after reconstruction of femoral condylar osteochondral defects using a novel hybrid reconstructive procedure, which was hypothesized to restore the contact characteristics to the intact condition. Controlled laboratory study. Tibiofemoral contact areas, contact forces, and mean contact pressures were measured in 8 cadaveric knees (mean age 52 ± 11 years; 6 women, 2 men) using a custom testing system and pressure mapping sensors. Five conditions were tested for each condyle: intact, 8-mm defect, 8-mm repair, 10-mm defect, and 10-mm repair. Medial femoral condylar defects were evaluated at 30° of knee flexion and lateral condylar defects were evaluated at 60° of knee flexion, with compressive loads of 50, 100, and 150 N. The defects were reconstructed with a titanium fenestrated threaded implant countersunk in the subchondral bone and an acellular dermal matrix allograft. Repeated-measures analysis of variance with Bonferroni correction for multiple comparisons was used to compare the results between the 5 testing conditions at each load. Medial condylar defects significantly increased mean contact pressure on the lateral side (P < .042), which was restored to the intact levels with repair. The lateral condylar defect decreased the mean contact pressure laterally while increasing the mean pressure medially. The lateral and medial mean contact pressures were restored to intact levels with the 8-mm lateral condylar defect repair. The medial mean contact pressure was restored to intact levels with the 10-mm lateral condylar defect repair. The lateral mean contact pressure decreased compared with the intact state with the lateral condylar 10-mm defect repair. Tibiofemoral joint contact pressure was restored to the intact condition after reconstruction of osteochondral defects with dermal allograft matrix and subchondral implants for the repair of both 8- and 10-mm lateral condylar defects as well as 8-mm medial condylar defects but not completely for 10-mm medial condylar defects. The novel hybrid procedure for osteochondral defect repair restored tibiofemoral joint contact characteristics to normal in a cadaveric model.

The Fibular Collateral Ligament Is a More Important Restraint to Varus Laxity Compared to the Anterolateral Complex in the Anterior Cruciate Ligament–Deficient Knee in a Cadaveric Biomechanical Study

PurposeThe purpose of this study was to compare the influence of the fibular collateral ligament (FCL) and the anterolateral complex (ALC) on varus knee laxity in paired anterior cruciate ligament (ACL)-deficient cadaveric knees using varus stress radiographs. MethodsVarus laxity in nine paired (N=18, mean age 73.8 years) human cadaveric knees was assessed using varus stress radiographs with a 12 Nm varus stress applied at 20° of knee flexion. All knees underwent testing in the intact state and following ACL sectioning. One knee of each pair was randomly assigned to undergo FCL sectioning and the contralateral knee was assigned to undergo ALC sectioning (anterolateral ligament [ALL] followed by the Kaplan fibers). ResultsBoth FCL sectioning and ALC (ALL and the Kaplan fibers) sectioning resulted in increased lateral compartment gapping compared to the intact state, 2.44 mm and 1.13 mm, respectively. ALL sectioning with intact Kaplan fibers did not result in increased lateral compartment gapping. Paired knee comparison revealed a significantly greater influence of the FCL than the ALC in restraining lateral compartment gapping under an applied varus stress (p=0.0003). ConclusionsSectioning the FCL resulted in significantly greater lateral compartment gapping under a varus stress than combined sectioning of the ALL and Kaplan fibers in an ACL deficient knee, although both scenarios resulted in significantly increased gapping compared to the intact state. Sectioning of the ALL with intact Kaplan fibers did not result in increased lateral compartment gapping. Clinical RelevanceThe FCL is the most important structure in restraining varus laxity in the ACL deficient knee and the ALC is of secondary importance in restraining varus laxity. In ACL deficient patients with a high-grade pivot shift, mild varus laxity on clinical examination, and an intact FCL on MRI, injury to the anterolateral complex should be considered and may be evaluated with varus stress radiographs. This study validates prior biomechanical studies of FCL deficiency and demonstrates that approximately 1 mm increase in lateral compartment gapping on varus stress radiographs may occur secondary to ALC injury and clinicians should be aware of this when considering treatment for ACL deficient patients with high-grade anterolateral laxity.

Generalization gap estimation for damage classification tasks when finite element simulated data is used for training: A numerical study and experimental validation on a steel truss

Labeled simulated structural responses by Finite Element (FE) methods may be used to construct training sets for monitoring the health state of structures. Such an approach appears to be an attractive way to avoid experimental costs. However, the main obstacle is the simulation error contained in such numerical responses. The error can contaminate the training data and lead to wrong conclusions when the learned features try to generalize on subsequent online experimental data. It is therefore very important to have an estimation of how good the available simulated data is for a given problem. The present work gives a novel methodology where classifiers trained by FE vibration response data are subjected to inputs of various perturbations, emulating in such way the generalization gap (classification errors) due to simulation errors. The response of the classifiers is gathered afterwards in a dataset which is used to construct a function that estimates the generalization gap based on the perturbed intact state response. Results are presented that show the behavior of the proposed gap estimation function for different binary damage classification scenarios. A numerical truss structure is used to test the concept. Convolutional Neural Networks (CNN) are applied for all data-driven related tasks, such as learning of health state features in vibration responses or evaluation of the gap function. The results show a promising methodology that can be used to estimate the reliability of numerically trained classifiers. In the final part of this study, the framework is tested on an experimental truss structure. The presented methodology contributes to the quantitative study of uncertainty when extrapolating from the numerical to the experimental domain in the presence of modeling errors.

Load Distribution After Serial Resection of the Posterior Horn of the Lateral Meniscus and Subsequent Meniscal Allograft Transplant: A Biomechanical Study

Background: Data are lacking as to when a meniscal allograft transplant (MAT) may be biomechanically superior to a partially resected lateral meniscus. Hypothesis: Lateral MAT using a bone bridge technique would restore load distribution and contact pressures in the tibiofemoral joint to levels superior to those of a partial lateral meniscectomy. Study Design: Controlled laboratory study. Methods: Eleven fresh-frozen human cadaveric knees were evaluated in 5 lateral meniscal testing conditions (native, one-third posterior horn meniscectomy, two-thirds posterior horn meniscectomy, total meniscectomy, MAT) at 3 flexion angles (0°, 30°, and 60°) under a 1600-N axial load. Pressure sensors were used to acquire contact pressure, contact area, and peak contact pressure within the tibiofemoral joint. Results: Limited (one-third and two-thirds) partial lateral posterior horn meniscectomy showed no significant increase in mean and peak contact pressures as well as no significant decrease in contact area compared with the intact state. Total meniscectomy significantly increased mean contact pressure at 0° and 30° (P = .008 and P < .001, respectively), increased peak contact pressure at 30° (P = .04), and decreased mean contact area in all flexion angles compared with the native condition (P < .01). Lateral MAT significantly improved mean contact pressure compared with total meniscectomy at 0° and 30° (P = .002 and P = .003, respectively) and increased contact area at 30° and 60° (P = .003 and P = .009, respectively), although contact area was still significantly smaller (24.1%) after MAT relative to the native meniscus (P = 0.015). However, allograft transplant did not result in better tibiofemoral contact biomechanics compared with limited partial meniscectomy (P > .05). Conclusion: The peripheral portion of the lateral meniscus provided the most important contribution to the distribution of contact pressure across the tibiofemoral joint in the cadaveric model. Total meniscectomy significantly increased mean and peak contact pressure in the cadaveric model and decreased contact area. Lateral MAT restored contact biomechanics close to normal but was not superior to the partially meniscectomized status. Clinical Relevance: Surgeons should attempt to preserve a peripheral rim of the posterior lateral meniscus. Meniscal allograft transplant appears to improve but not normalize mean contact pressure and contact area relative to total lateral meniscectomy.

Detecting failed tethers in submerged floating tunnels using an LSTM autoencoder and DNN algorithms

This study proposes a two-step approach for detecting damaged tethers in submerged floating tunnels. The proposed method employs two different artificial neural network algorithms. First, the long short-term memory (LSTM) autoencoder model trained using response datasets under intact conditions was used to reconstruct the measured acceleration data of the target structure. Further, the data reconstruction error was used as the input for the deep neural network algorithm trained in advance using the reconstruction error pattern in various tether damage cases. The proposed method was verified by conducting a well-validated simulation based on hydrodynamics. The damage-detection accuracy of the proposed method was directly compared with that of a conventional supervised learning algorithm-based approach. In addition, the case study results confirmed that the proposed approach was applicable to other submerged floating tunnel (SFT) structures by retraining the LSTM autoencoder and deep neural network algorithms with intact datasets only. Thus, this approach does not require a large amount of training data or simulation model updates for other SFT structures.

Crossing the Cervicothoracic Junction: A Biomechanical Investigation of C7 vs T1 Caudal Selection's Effect on Adjacent Segment Motion in Posterior Cervical Fusion.

Biomechanical Study. This study aims to evaluate the biomechanical adjacent segment effects of multi-level posterior cervical fusion constructs that terminate at C7 compared to those that terminate at T1 in cadaveric specimens. The cervicothoracic junction poses unique challenges for spine surgeons. Deciding to terminate multi-level posterior cervical fusion constructs at C7 or extend them across the cervicothoracic junction remains a controversial issue. Six cadaveric specimens underwent biomechanical testing in the intact state and after instrumentation with constructs from C3 and terminating at either C7 or T1. Range of motion (ROM) was assessed in flexion-extension, lateral bending, and axial rotation globally and at cranial and caudal adjacent segments. There was a significant decrease in overall flexion/extension by both C7 (-35.5°, P=0.002) and T1 (-39.8°, P=0.002) instrumentation compared to the intact spine. T1 instrumentation had significantly lower (-4.3°, P=0.008) flexion/extension ROM compared to C7 instrumentation. There were significant decreases in axial rotation by both C7 (-31.4°, P=0.009) and T1 (-36.8°, P=0.009) instrumentation compared to the intact spine, but no significant differences were observed between the two. There were also significant decreases in lateral bending by both C7 (-27.9°, P=0.022) and T1 (-33.7°, P=0.022) instrumentation compared to the intact spine, but no significant differences were observed between the two. No significant differences were observed in ROM at cranial or caudal adjacent segments between constructs terminating at C7 and those extending to T1. This biomechanical investigation demonstrates that constructs that cross the cervicothoracic junction experience less overall spinal motion in flexion-extension compared to those that terminate at C7. However, contrary to prior studies there is no difference in cranial and caudal adjacent segment motion. Surgeons should make clinical decisions regarding the caudal extent of fusion in multi-level posterior cervical fusions without major concerns about adjacent segment motion.

Stage-dependent role of interhemispheric pathway for motor recovery in primates

Whether and how the non-lesional sensorimotor cortex is activated and contributes to post-injury motor recovery is controversial. Here, we investigated the role of interhemispheric pathway from the contralesional to ipsilesional premotor cortex in activating the ipsilesional sensorimotor cortex and promoting recovery after lesioning the lateral corticospinal tract at the cervical cord, by unidirectional chemogenetic blockade in macaques. The blockade impaired dexterous hand movements during the early recovery stage. Electrocorticographical recording showed that the low frequency band activity of the ipsilesional premotor cortex around movement onset was decreased by the blockade during the early recovery stage, while it was increased by blockade during the intact state and late recovery stage. These results demonstrate that action of the interhemispheric pathway changed from inhibition to facilitation, to involve the ipsilesional sensorimotor cortex in hand movements during the early recovery stage. The present study offers insights into the stage-dependent role of the interhemispheric pathway and a therapeutic target in the early recovery stage after lesioning of the corticospinal tract.

Dynamic contrast enhancement and wall enhancement index for the quantitative assessment of vascular wall abnormalities in intracranial atherosclerosis: a pilot study

Background: Breakthrough neurotechnologies have allowed for new understanding of some brain disorders; however, identification and differential diagnosis of intracranial stenotic and occlusive lesions remains challenging. Magnetic resonance imaging (MRI) with dynamic contrast enhancement (DCE) is a tool that could be used for the quantitative assessment of endothelial permeability and microvascular volume in atherosclerotic plaques (AP). Aim: To assess quantitative parameters of vascular wall abnormalities in AP area and in obviously unchanged wall of intracranial arteries with MRI DCE and high spatial resolution Т1-weighed images before and after contrast injection, with calculation of the wall enhancement index (WEI) by mathematical modelling. Methods: This was a pilot cross-sectional uncontrolled study with consecutive recruitment of 29 patients with atherosclerotic abnormalities of brachiocephalic arteries, including intracranial. The patients’ median age was 66 [57; 72] years; they were mostly men (75.9%, n = 22). For the assessment of any brain abnormalities, MRI (magnetic induction 3 Tesla, Magnetom Prisma, Siemens) was performed in patients with standard sequence (Т2, T2-FLAIR), as well as MRI DCE for the assessment of intracranial arteries, before and after intravenous contrast injection, with high spatial resolution T1-weighed imaging and suppression of the signal from bloodstream and fat, with the calculation of WEI. Results: There were significant differences in WEI in AP and in unchanged wall (0.962 [0.686; 1.387] vs. 0.111 [0.014; 0.206], p 0.001). No significant differences were found between WEI values in internal carotid arteries APs (0.722 [0.573; 1.580]), middle cerebral arteries (0.921 [0.725; 1.183]), and basilar artery (1.343 [1.002; 1.419]) (p = 0.381). We also found significant difference (p = 0.034) in the extravascular extracellular fraction volumes ve (Tofts) in AP located in the basilar artery (0.171 [0.146; 0.325]), internal carotid arteries (0.579 [0.358; 1.000]), and middle cerebral arteries (0.134 [0.101; 0.269]). Conclusion: This is the first description of quantitative parameters characterizing vascular wall abnormalities in intracranial atherosclerosis. Despite its obviously intact state, vascular walls outside the intracranial AP was shown to be abnormal as well.

Superior Capsular Reconstruction using the Long Head of Biceps Tendon: A Biomechanical Assessment of Tenodesis Location and Angle of Fixation

BackgroundMassive irreparable rotator cuff tears (MIRCT) treated with superior capsular reconstruction (SCR) using the long head of the biceps tendon have shown satisfactory early results. Different techniques and positions for biceps tenodesis have been described. This study aimed to evaluate the effect of tenodesis location and glenohumeral fixation angle for graft tensioning on the biomechanics of a SCR using a single strand biceps technique. MethodsEight cadaveric shoulders were mounted to a custom biomechanical simulator which employed static tone loads to the deltoid and rotator cuff muscles. All cadavers were first tested in the intact condition, and then in the simulated MIRCT condition by sectioning the tendinous insertions of the supraspinatus and upper border of the infraspinatus. SCR using the long head of the biceps tendon was then evaluated. Three biceps tenodesis locations relative to the greater tuberosity (anterior, middle, and posterior) and two glenohumeral fixation angles (0° and 30°) for graft tensioning were tested. An optical tracking system was used to quantify superior-inferior (SI) and anterior-posterior (AP) humeral head translation relative to the glenoid, while the functional abduction force was quantified using a load sensor. All tests were conducted at 0°, 30° and 60° of glenohumeral abduction in a randomized fashion. ResultsWhen assessing isolated superior humeral head migration, all biceps tenodesis locations were effective at decreasing superior migration, with no tenodesis location significantly better than the other (P=0.213). However, biceps grafts tensioned at 30° of glenohumeral abduction were significantly better at reducing proximal humeral migration as compared to graft tensioning at 0° abduction (P=0.008).Posterior humeral head translation observed in the MIRCT condition was significantly reduced when tensioning the biceps tendon at 30° of glenohumeral abduction compared to 0° for all tenodesis locations (P≤0.043). Tenodesis location also significantly influenced posterior humeral head translation (P=0.001), with middle and posterior positions restoring near normal humeral head position when fixed at 30° glenohumeral abduction. All SCR techniques using the biceps tendon improved the functional abduction force relative to the MIRCT condition, although no statistically significant differences were observed relative to the intact condition (P≥0.448). DiscussionSCR using the long head biceps tendon is biomechanically effective in reducing posterosuperior translation of the humeral head in the setting of a MIRCT. Graft tensioning and fixation at 30° of glenohumeral abduction combined with either a middle or posterior tenodesis location on the greater tuberosity most effectively restores near normal time-zero humeral head kinematics.