Direction Of Displacement Research Articles

UNDERSTANDING THE BIOMECHANICAL RESPONSE OF PROGRESSIVE THREAD DENTAL IMPLANTS USING MULTI-SCALE FINITE ELEMENT ANALYSIS

Implant osseointegration is an important factor dictating its long-term efficacy in situ. Along with various biological factors, it is greatly influenced by the mechanical stimulus at the peri-implant bone. The present study aims to understand the biomechanical response of progressive thread dental implants using multi-scale-based finite element analysis employing macro and micro models of bone. μ-CT images of a cadaveric human mandible of its premolar region were obtained, along with CT scan of the same region to generate computational models. Total of six dental implants were designed having regular and progressive thread depths. Three different stages of healing of the bone-implant assembly were simulated parametrically. The biomechanical environment at the peri-implant bone was analyzed considering the 'Mechanostat' hypothesis. The obtained results revealed that bone strain is significantly higher during the initial healing phase when the bone is weakest. During this phase, implant stress and its displacement in both buccolingual and coronoapical directions are also noticeably higher. Also, displacements of progressive thread implants were lower in all the healing phases as compared to the implants with constant thread depth. The observations of this μ FEA study highlights the clinical applicability of a progressive thread dental implant as it generates larger functional surface area, thus engages higher trabeculae and therefore is suitable for weaker bone conditions. Furthermore, by comparing the stress values at bone and implant between the two bone models, the CT-based model having inhomogeneous material was deemed suitable as an alternative to computationally expensive μ FEA.

Comparison of the Effects of Cognitive Dual-Task and Single-Task Balance Exercises on Static Balance among People with Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial.

The anterior cruciate ligament (ACL) reconstruction surgery improves mechanical stability; however, functional stability remains impaired. Balance exercises can help improve functional stability. The effect of cognitive dual-task balance exercises has not been studied in people with ACL reconstruction surgery; therefore, this study aimed to compare the effect of cognitive dual-task and single-task balance exercises on the static balance indices in these individuals. This study was a randomized clinical trial. After a period of conventional physiotherapy and applying inclusion criteria, 28 patients with ACL reconstruction surgery were randomly divided into two groups of cognitive dual-task and single-task balance exercises. Each group received the relevant exercises for four weeks, three times a week, with each session lasting 20 min. Center of pressure variables, including mean displacement in anterior-posterior and medial-lateral directions, total path length, mean velocity of displacement, root mean square of displacement and velocity, and the elliptical area, were measured using the FDM pressure platform before and after the interventions as the primary outcomes. Knee Injury and Osteoarthritis Outcome Score (KOOS) scale was completed by the participants before and after the interventions. The measured static balance variables and KOOS subscales had significant differences before and after intervention in both groups (P<0.05); however, no statistically significant difference was observed in these variables between the two groups. There was no significant correlation between KOOS subscales and measured static balance variables. Both cognitive dual-task and single-task balance exercises improved the indicators related to static balance and the level of functional disability of the knee. However, cognitive dual-task balance exercises had no superiority over single-task balance exercises in ACL-reconstructed individuals.

Along-Track Displacement of Mw 7.8 and 7.6 Kahramanmaraş Earthquakes from Sentinel-1 Offset Tracking and Burst Overlap Interferometry

On 6th February, a pair of significant earthquakes with magnitudes of 7.8 and 7.6 struck Kahramanmaraş, Turkey. The Earthquake InSAR Data Provider (EIDP) promptly produced interferograms and offset tracking results within 3 hours of acquiring Sentinel-1 satellite data. However, it was challenging to unwrap the interferograms correctly due to high displacement gradient near the rupture. Hence, early displacement fields were derived from Pixel Offset Tracking (POT) method both in range and azimuth direction with low resolution depending on pixel sizes of Sentinel-1. We used the Burst Overlap Interferometry (BOI) method to extract the accurate along-track displacement and unwrapped the BOI interferogram using Azimuth Offset Tracking (AOT) data as a guide. Combining the unwrapped BOI interferogram and the AOT data, we derive a high-quality along-track displacement field that illuminates the entire earthquake rupture over 350 km and exhibits ±4 m displacement in the along-track direction.

Measuring the global mechanical properties of the human thorax: Costo-vertebral articulation

Biomechanical simulation of the human thorax, e.g. for 3D-printed rib implant optimisation, requires an accurate knowledge of the associated articulation and tissue stiffness. The present study is focusing on determining the stiffness of the costo-vertebral articulations.Specimens of rib segments including the adjacent thoracic vertebrae and ligaments were obtained from two human post-mortem bodies at four different rib levels. The rib samples were loaded with a tensile force in the local longitudinal, sagittal and transverse direction and the resulting displacement was continuously measured. The moment–angle response of the rib articulations was also determined by applying a load at the rib end in the cranial – caudal direction and measuring the resulting displacement.The torsional load response of the costo-vertebral articulations at an applied moment between −0.1 Nm and 0.1 Nm corresponded to a median range of motion of 13.2° (6.4° to 20.9°). An almost uniform stiffness was measured in all tensile loading directions. The median displacement at the defined force of 28 N was 1.41 mm in the longitudinal, 1.55 mm in the sagittal, and 1.08 mm in the transverse direction.The measured moment–angle response of the costo-vertebral articulation is in line with the data from literature. On the contrary, larger displacements in longitudinal, sagittal and transverse directions were measured compared to the values found in literature.

3D PRINTING IN COMPLEX TIBIAL FRACTURE CLASSIFICATION & PLANNING.

Tibial plateau fractures are common intra-articular fractures that pose classification and treatment challenges for orthopedic surgeons. This study examines the value of 3D printing for classifying and planning surgery for complex tibial plateau fractures. We reviewed 54 complex tibial plateau fractures treated at our hospital from January 2017 to January 2019. Patients underwent preoperative spiral CT scans, with DICOM data processed using Mimics software. 3D printing technology created accurate 1:1 scale models of the fractures. These models helped subdivide the fractures into seven types based on the tibial plateau's geometric planes. Surgical approaches and simulated operations, including fracture reduction and plate placement, were planned using these models. The 3D models accurately depicted the direction and extent of fracture displacement and plateau collapse. They facilitated the preoperative planning, allowing for precise reconstruction strategies and matching intraoperative details with the pre-printed models. Post-surgery, the anatomical structure of the tibial plateau was significantly improved in all 54 cases. 3D printing effectively aids in the classification and preoperative planning of complex tibial plateau fractures, enhancing surgical outcomes and anatomical restoration. Level of Evidence IV, Prospective Study.

Topology optimization using artificial intelligence

An analysis of topology optimization employing deep learning, namely Generative Adversarial Networks (GANs), and topology optimization utilizing the Solid Isotropic Material with Penalization (SIMP) method is presented in this research. We describe the theoretical foundations of GANs and the SIMP technique. A cantilever beam with predetermined boundary conditions was the topic of a static study to show the practical efficacy of these methods. The structural performance parameters, such as maximal directional displacement, maximal Von Mises stress, and deformation energy. The findings show that deep learning-based topology optimization, as demonstrated by TopologyGAN, provides considerable benefits in terms of improved design correctness and computing performance.

Effect of macular pigment optical density on Yellow‐Blue and Red‐Green colour discrimination

The macular pigment (MP) absorbs preferentially short‐wavelength light and its narrow spectral absorption curve overlaps mostly the spectral responsivity function of S‐cones, although the M‐ and L‐cones are also affected. The MP is restricted to the centre ~14° disc region of the retina with a peak optical density (OD) at the centre in the range 0 to 1 log units. Although the macular pigment optical density (MPOD) decreases rapidly with increasing eccentricity, carotenoid supplementation studies reveal a large uptake of lutein and zeaxanthin, particularly in the parafoveal region and covering the centre ~6° to 8° of the fovea (doi: 10.1111/j.1475‐1313.2006.00386.x).Since the MP contributes to the reduced excitation of S‐cones, it is of interest to examine the effects MP may have on colour vision, particularly when ‘blue‐blocking’ lenses are also involved. We studied the relationship between MPOD and red/green (RG) and yellow/blue (YB) colour thresholds by measuring the spatial distribution of the MP in normal trichromats using the Macular Assessment Profile (MAP) test (doi: 10.1111/j.1475‐1313.2010.00748.x) and the corresponding RG and YB colour thresholds using the CAD test (doi:10.1093/bmb/ldx007).The results show negligible correlation between peak MPOD and YB thresholds and a small, but significant negative correlation with RG thresholds. This observation is of interest since increased MPOD values result in lower RG thresholds. The same experiment was also carried out in subjects with significantly larger amounts of MP following 3 months of supplementation with carotenoids. When averaged over the centre disc region of 2.5° and then over a parafoveal annulus between 2.5° and 4°, the corresponding, mean MP densities show only negligible correlations with RG and YB colour thresholds. To explain these findings, we calculated the expected cone‐contrasts for S‐, M‐ and L‐cones for chromatic displacements defined by the threshold ellipse. The results show that MP absorption of short‐wavelength light has a negligible effect on S‐cone contrast over the whole range of displacement directions associated with the colour threshold ellipse. Repeated calculations with simulated MPOD values up to 1 log unit, produced the same result. More recently, we modelled the effects ‘blue‐blocking’ lenses and pre‐receptor filters in the eye to explore changes to the orientation and the size of the colour threshold ellipse. The model predicts well the measured RG and YB thresholds and confirms the absence of significant threshold changes for MPOD values in the range 0 to 1 log unit. The model does, however, predict systematic changes in the orientation of the major axis (i.e., the tritan axis) and MPOD. These observations are of interest since the orientation of the major axis of the best‐fit ellipse appears to decrease monotonically from ~75° to 55°, as MPOD increases from very small values up to a peak OD of 1 log unit. More work is needed to investigate how YB and RG chromatic sensitivity is affected by combined absorption of short‐wavelength light by MPOD, the lens of the eye and ‘blue‐blocking’ spectacle lenses.

Analysis of Lateral Displacement of Pile Foundation Caused by Large-Diameter Shield Tunneling

The aim of this research is to study the lateral deformation characteristics of the pile foundation in front of a shield construction and accurately predict its displacement in the shield tunneling direction. The impact of deep-shield construction on the pile foundations was analyzed using the Mindlin elastic solution to determine the lateral displacement. The Kerr foundation model and other factors, like additional shield thrust and uneven shell friction, were considered. The study assessed the impact of the incision distance, shield outer diameter, and additional thrust on pile displacement. The theoretical and numerical solutions of lateral displacement at various shield construction stages were compared to determine the variation law. The results indicate that the theoretical method is reliable, considering its good agreement with the numerical solutions. The buried depth of the shield means that the upper part of the pile is less affected by the additional thrust, leading to less deformation at the top. We recommend using a smaller shield thrust and outer diameter to control the pile’s end and top displacement.

Postural stability assessment in expert versus amateur basketball players during optic flow stimulation

We evaluated the role of visual stimulation on postural muscles and the changes in the center of pressure (CoP) during standing posture in expert and amateur basketball players. Participants were instructed to look at a fixation point presented on a screen during foveal, peripheral, and full field optic flow stimuli. Postural mechanisms and motor strategies were assessed by simultaneous recordings of stabilometric, oculomotor, and electromyographic data during visual stimulation. We found significant differences between experts and amateurs in the orientation of visual attention. Experts oriented attention to the right of their visual field, while amateurs to the bottom-right. The displacement in the CoP mediolateral direction showed that experts had a greater postural sway of the right leg, while amateurs on the left leg. The entropy-based data analysis of the CoP mediolateral direction exhibited a greater value in amateurs than in experts. The root-mean-square and the coactivation index analysis showed that experts activated mainly the right leg while amateurs the left leg. In conclusion, playing sports for years seems to have induced some strong differences in the standing posture between the right and left sides. Even during non-ecological visual stimulation, athletes maintain postural adaptations to counteract the body oscillation.

Characterization of the Fels Landslide (Alaska) Using Combined Terrestrial, Aerial, and Satellite Remote Sensing Data

The characterization of landslides located in remote areas poses significant challenges due to the costs of reaching the sites and the lack of reliable subsurface data to constrain geological interpretations. In this paper, the advantages of combining field and remote sensing techniques to investigate the deformation and stability of rock slopes are demonstrated. The characterization of the Fels landslide, a large, slowly deforming rock slope in central Alaska, is described. Historical aerial imagery is used to highlight the relationship between glacier retreat and developing instability. Airborne laser scanning (ALS) and Structure-from-Motion (SfM) datasets are used to investigate the structural geological setting of the landslide, revealing a good agreement between structural discontinuities at the outcrop and slope scales. The magnitude, plunge, and direction of slope surface displacements and their changes over time are studied using a multi-temporal synthetic aperture radar speckle-tracking (SAR ST) dataset. The analyses show an increase in displacement rates (i.e., an acceleration of the movement) between 2010 and 2020. Significant spatial variations of displacement direction and plunge are noted and correlated with the morphology of the failure surface reconstructed using the vector inclination method (VIM). In particular, steeper displacement vectors were reconstructed in the upper slope, compared to the central part, thus suggesting a change in basal surface morphology, which is largely controlled by rock mass foliation. Through this analytical approach, the Fels landslide is shown to be a slow-moving, compound rockslide, the displacement of which is controlled by structural geological features and promoted by glacier retreat.

Neutral inhomogeneity in circular cylinder subjected to prescribed boundary displacement

In this paper a single circular inhomogeneity embedded within a solid circular cylinder whose curved boundary surface is subjected to a given boundary displacement in axial direction is considered. The displacement neutrality of the coupled system of host body and inclusion is studied. The neutral inhomogeneity (inclusion) does not disturb the displacement, strain and stress fields in the host body. In this paper the deformation of the considered inhomogeneous cylinder is a linear antiplane shear deformation.

Numerical Investigation on the Influence of Super-Large-Diameter Shield Tunneling on Nearby Existing Metro Tunnels and the Protection Scheme

To reduce traffic congestion and meet the demand for rail transportation, the diameters of shield tunnels are constantly expanded. The super-large diameter, deep depth and long distance of super-large-diameter shield tunnels, coupled with the limitation of existing structures on underground construction space, cause many problems in the construction of these tunnels, such as affecting existing structures. This study takes a shield project in Wuhan as the research object, uses the finite element method to simulate the influence of super-large-diameter shield tunnelling on the displacement of the existing Line 5 tunnel segments, and analyzes the influence of the isolation pile arrangement and length on the isolation effect. The analysis indicates that (1) the displacement of Line 5 decreases with an increasing horizontal center distance between the tunnels and increases with an increasing vertical center distance between the tunnels, with a maximum displacement of 17.9 mm; (2) the displacement direction and position of the maximum displacement of Line 5 vary with changes in the vertical center distance between the tunnels, but remain essentially constant with changes in the horizontal center distance; and (3) the isolation piles closer to the shield tunnel improve support, with its isolation effect on the Line 5 segment becoming limited.

Immediate effects of local muscle vibration on static and dynamic balance control in individuals with chronic ankle instability

ObjectivesTo investigate the immediate effects of local muscle vibration (LMV) on static and dynamic balance control in individuals with and without chronic ankle instability (CAI). DesignQuasi-experimental study. SettingResearch laboratory. ParticipantsTwenty-six individuals with CAI and 26 healthy controls. Main outcome measuresCenter of pressure variables (mean total velocity and displacement in anteroposterior (AP) and mediolateral (ML) directions) during single-leg standing with eyes open and eyes closed and also reach distances in anterior (ANT), posteromedial (PM), and posterolateral (PL) directions of the modified star excursion balance test (MSEBT) were assessed before and after LMV. ResultsStatistical analyses showed a significant decrease in mean total velocity and displacement in AP direction from before to after LMV in eyes open condition for both individuals with CAI (p = 0.025, p = 0.041, respectively) and healthy controls (p = 0.001, p = 0.003, respectively). Similar results were observed in eyes closed condition for both individuals with CAI (p < 0.001, p < 0.001, respectively) and healthy controls (p = 0.040, p = 0.014, respectively). The results also showed increased reach distances in ANT (p < 0.001), PM (p < 0.001), and PL directions (p < 0.001) in all participants after LMV. ConclusionOur results suggest that LMV may be a useful tool in rehabilitation of static and dynamic balance deficits in individuals with CAI.

Bilateral abducens nerve palsy from post-spinal-anesthesia-induced bilateral chronic subdural hematoma: case report

BackgroundA chronic cranial subdural hematoma arising after post-spinal anesthesia is a rare but serious and life-threatening complication of spinal anesthesia. It usually mimics the typical post-spinal-anesthesia headache or post-dural-puncture headache, potentially masking its detection. Abducens nerve palsy tends to occur in chronic subdural hematoma of post-dural-puncture etiology rather than in cases attributed to other causes of subdural hematoma. Preferential damage to the abducens nerve is frequent and can be attributed to its anatomic course because the abducens nerve runs in the direction of the typical caudad displacement of the brain related to intracranial hypotension.ObservationHere, we present a report on the clinical presentation, pathogenesis, and management of two cases that developed bilateral abducens nerve palsy following post-spinal anesthesia administered for cesarean sections due to obstetric indications.LessonPost-spinal-anesthesia-induced chronic subdural hematoma, although a rare, life-threatening complication, must be differentiated from post-spinal-anesthesia headache and treated surgically. Cranial nerve palsy (more commonly called abducens nerve palsy) is more common in post-spinal-anesthesia-induced subdural hematoma than subdural hematomas of other etiologies as the cerebrospinal fluid brain cushioning is partly lost. Cranial nerve palsies resolve in most cases if surgery is performed in a timely manner.

Shaking table test of the seismic performance for railway simply-supported girder bridge isolated by self-centering bearing

In order to solve the problem of the residual displacement of a railway simply-supported girder bridge and realize the aim of a rapid recovery in traffic after earthquake events, we designed a self-centering seismic isolation bearing and created a typical simply-supported girder bridge model with 1/10 ratio. Three peak ground acceleration (PGA) shaking table tests were performed, with the test procedures further described in detail. The test results show that the bearing provides an overall good self-centering performance. Other than the case of a 0.5 g transverse earthquake, where the bearing remains outside of the sliding surface and therefore cannot be self-centering, all the tests show that the bearing is completely self-centering. At the same time, during all the earthquake scenarios, the main structure of the bridge was not damaged in any discernable way, the longitudinal frequency did not change, and the transverse frequency decreased given that the bearing remained outside of the sliding surface. In addition, it was found that the large bearing displacement in the longitudinal direction may lead to a collision of adjacent girders, resulting in a sharp increase in the acceleration of the girders. In cases without collisions between the girders, the acceleration of the girder is effectively reduced compared with the acceleration of the pier top. The results also show that the pier can be effectively protected by the self-centering bearing, as well as indicating that the reinforcement strain of the pier does not reach the yield value under all tests. Due to the large displacement of the bearing, it is necessary to increase the allowable displacement or install a limiting device. Finally, the finite element model (FEM) of the test model is established, with the calculation results compared with the test results, in this way proving the correctness of the FEM and providing a reference for designing the seismic isolation of the railway simply-supported girder bridge.

Injury to the posterior malleolus in Maisonneuve fractures

PurposeThe aim of this study was to describe the incidence and a complex pathoanatomy of posterior malleolus fractures in a Maisonneuve fracture.MethodsThe study included 100 prospectively collected patients with a complete clinical and radiological documentation of an ankle fracture or fracture-dislocation including a fracture of the proximal quarter of the fibula.ResultsA posterior malleolus fracture was identified in 74 patients, and in 27% of these cases it carried more than one quarter of the fibular notch. Displacement of the posterior fragment by more than 2 mm was shown by scans in 72% of cases. Small intercalary fragments were identified in 43% of cases. Fractures of the Tillaux–Chaput tubercle were identified in 20 patients.ConclusionOur study has proved a high rate of posterior malleolus fractures associated with a Maisonneuve fracture, and documented their considerable variability in terms of involvement of the fibular notch, tibiotalar contact area, direction of displacement and frequency of intercalary fragments. Of no less importance is a combination of Tillaux–Chaput fractures with a Maisonneuve fracture.

Investigation of edge effect on wurtzite gallium nitride in nanoindentation using molecular dynamics simulation

In practical applications, block materials frequently experience edge collapse, yet our grasp of this phenomenon at the nanoscale remains limited. Understanding this is crucial, as nanoscale material behaviors can trigger intricate microscale effects that elude easy observation or comprehension at the macroscopic level. This work researched the edge effect of the wurtzite GaN with {0001} surface crystal orientation at different nanoindentation distances by molecular dynamics simulation. The results show that the GaN indentation edge effect is anisotropic. The atomic displacement directions prolonged [2–1–10], [–12–10], and [–1–120], which is hexagonal distributing, similar to the crystal structure. The dislocations are around the indenter and close to the upper surface, similar to the negative von Mises stress distributions. The closer the indenter is to the edge of the sample, the more atoms are extruded from the specimen edge, and the more serious the damage is to the edge generally. However, analysis of the mechanical response and phase transition shows that the damage to the edge can be weakened while the crystal structure is destroyed more severely at some specific locations of the indenter. This work reveals the evolution of GaN crystal structure under different nanoindentation distances and the mechanism of squeeze-out atoms from the edge at the atomic scale.

Need for (expected) speed: Exploring the indirect influence of trial type consistency on representational momentum

The biases affecting people’s perception of dynamic stimuli are typically robust and strong for specific stimulus configurations. For example, representational momentum describes a systematic perceptual bias in the direction of motion for the final location of a moving stimulus. Under clearly defined stimulus configurations (e.g., specific stimulus identity, size, speed), for example, the frequently used “implied motion” trial sequence, for which a target is subsequently presented in a consistent direction and with a consistent speed, a displacement in motion direction is evidenced. The present study explores the potential influence of expectations regarding directional as well as speed consistencies on representational momentum, elicited by including other, inconsistently moving trial types within the same experimental block. A systematic representational momentum effect was observed when only consistent motion trials were presented. In contrast, when inconsistent target motion trials were mixed within the same block of experimental trials, the representational momentum effect decreased, or was even eliminated (Experiments 1 & 2). Detailed analysis indicated that this reflects a global (proportion of consistent and inconsistent motion trials within a particular experimental block), not local (preceding trial influencing actual trial) effect. Yet, additional follow-up studies (Experiments 3 & 4) support the idea that these changes in perceived location are strongly influenced by the overall stimulus speed statistics in the different experimental blocks. These results are discussed and interpreted in light of recent theoretical developments in the literature on motion perception that highlight the importance of expectations about stimulus speed for motion perception.

Magnetic tunnel junction platforms for linear positioning and nanoscale displacement sensing

An array of magnetic tunnel junctions (MTJs), connected in a Wheatstone bridge, is characterized as a positioning sensor to detect spatial displacement of a magnetized object. To perform the experiment, the sensor was mounted on a fixed frame, and the magnet was installed on top of nano-positioning piezo-stage, operating in a closed-loop feedback circuit. The sensor signal was recorded in time domain, to detect displacement of the magnet, defined by commands to the stage. The positioning transfer curves were obtained for different orientations of magnetization with respect to the direction of the magnet displacement and the field sensing direction of the MTJs in the arrays. For configurations with linear transfer curve between positioning displacements and the sensor signal, the effects of magnet size, sensor pattern dimensions and interspace distance between the sensor and magnet positioning trajectories, are characterized. In the optimized experimental configuration, the displacement steps down to 10 nm were detected.

The effects of abrasive moving speed and motion mode on the thinning mechanism of SiC in three-body contact

Three-body contact is the main contact type in polishing process and leads to a different thinning mechanism than the two-body contact. Molecular dynamics simulation is employed to investigate the thinning mechanism of 3C-SiC substrate in three-body contact. The thinning mechanisms of 3C-SiC under different moving speeds and motion modes of diamond abrasive are compared. Through the analysis of force, temperature, potential energy, stress distribution and atomic flow field, the causes of different thinning mechanisms are explained. It is found that the influence of moving speed is mainly reflected in the temperature rise of substrate when the motion mode of abrasives is the same. The changes of motion mode will significantly alter the stress distribution, which is closely related to the damage depth and atomic flow field. When the feed speed is the same, increasing the self-rotation speed of abrasives can reduce concentration zone of hydrostatic stress and then reduce the damage depth. The self-rotation of abrasives will also change the distribution of von Mises stress, resulting in the different displacement directions of 3C-SiC atoms. Dislocations are more easily generated when the displacement direction of SiC atoms is the same. The moving speed of abrasive is found to have little effect on the thinning mechanism, while the motion mode of abrasive will significantly change the thinning mechanism.