Backward Displacement Research Articles

An enhancing flexibility piezoelectric stick-slip actuator by introducing perforation of flexible hinge

Piezoelectric stick-slip actuators (PSSAs) utilize sliding friction between the mover and stator to convert and transmit motion. However, the phenomenon of backward displacement often hinders the output performance of PSSAs. This paper proposes a method to mitigate backward displacement and enhance output performance by modifying the overall flexibility of the actuator. The key idea of this approach is to propose a novel flexible hinge structure and apply it to PSSA. Numerical calculations and finite element analysis confirm that the flexibility and output performance of the PSSA are significantly improved. The method's feasibility is supported by comparing experiments. The experimental results show that under the same locking force, the optimal excitation frequency of perforated Elliptical Flexure Hinge (EFH) is significantly lower than the non-perforated EFH and the speed is increased over 53 %. Furthermore, the PSSA has a maximum load capacity of 190 g, which is 31.7 times its own weight (6 g). The proposed PSSA can provide valuable insights for its application in precision motion control systems in the foreseeable future.

Research on positioning accuracy of the swivel head of milling and turning complex machining center

Abstract This article focuses on the swivel head of a milling-turning complex machining center and establishes a geometric error model between the rotary axes based on the multi-body system theory and the homogeneous coordinate transformation method. The double ball bar (DBB) is used to identify the geometric errors of the machine tool swivel head position-independent by measuring circular trajectories. The impact of PIGEs on the measurement trajectory is simulated. The swivel head is rotated at four angles (B0°, B45°, B90°, B-15°), and the laser tracker is used to analyze and study the linear axis straightness, perpendicularity, and the center coordinates and plane errors of the swivel head movement along the XZ plane. A swivel head rotation accuracy test fixture is designed to correct the positioning accuracy of a swivel head with a 45° inclination of the rotation axis. The research results show that the fluctuation of the center plane degree of freedom of the swivel head moving along the XZ plane is small, and the maximum value is 0.0086mm. Under the 45° angle posture of the swivel head, both the center coordinate error value and the plane error value are the largest. The simulation results of the swivel head position error are fairly consistent with the center coordinate error of the swivel head plane movement. A backward tilt displacement of 0.01mm~0.015mm of the machine column during assembly can reduce the influence of the weight of the swivel head on the perpendicularity and straightness of the vertical reciprocating motion, and adding auxiliary support near the base of the swivel head zero position can reduce machine straightness error.

Posterior corneal stability after small incision lenticule extraction with different optical zones.

To assess the changes in the posterior corneal surface following small incision lenticule extraction (SMILE) with different optical zones. In this retrospective study, 106 eyes of 106 patients who underwent SMILE were recruited 3 years after the procedure. Eyes were divided into two groups according to the size of the surgical optical zone: group A (52 eyes, ≤6.2 mm) and group B (54 eyes, ≥6.5 mm). Posterior central elevation (PCE) and 12 other points at 45°, 135°, 225° and 315° with distances of 1 mm, 2 mm and 3 mm from the centre were recorded from Pentacam. No iatrogenic keratectasia was identified, and eyes in the two groups showed comparable visual results. The overall trend in posterior corneal elevation changes was consistent for both groups. PCE decreased significantly from 1.33 ± 2.32 to 0.75 ± 2.41 in group A (P = 0.024) and from 0.87 ± 2.61 to 0.06 ± 2.74 in group B (P = 0.003). All points in the central 2 mm region in both groups were reduced postoperatively. In the 4 mm and 6 mm corneal annulus, almost all points at 225°and 315° showed backward displacement, with the most prominent change occurring at 315° in the 6 mm annulus (P < 0.001), indicating no forward protrusion in the inferior area. No forward protrusion in the posterior corneal surface was observed 3 years after SMILE with different optical zones. Comprehensive preoperative measurements are essential for ensuring corneal stability and avoiding iatrogenic keratectasia.

Effects of volume ratios of tongue and oral cavity on upper airway in skeletal Class II cases

Abstract Background The relationship between tongue volume and oral cavity volume (TV/OCV) ratio and upper airway volume is of great interest especially in skeletal Class II cases because they are commonly associated with retruded mandible as seen in Class II div. 1. It results in backward displacement of the tongue and hyoid bone causing reduction in the upper airway volume. This reduction in the upper airway volume is a causative factor for some common respiratory disorders such as obstructive sleep apnea syndrome. Aim The present study was carried out to find the effect of tongue size and oral cavity size and their ratio on the upper airway volume in skeletal Class II cases. Methods A cross-section study was performed on cone beam computed tomography images of 40 skeletal Class II patients whose age ranges from 17 to 22 years old. The volume of the nasopharyngeal airway, oropharyngeal airway, hypopharyngeal airway, nasoethmoid cavity (nasal cavity and ethmoid sinus), right and left maxillary sinus and oral cavity airway were calculated by using materialize Mimics Medical, Version 21.0. Correlation of each segment with TV/OCV ratio was detected. Results It was found that TV/OCV ratio had a significant positive correlation with TV (P &lt; 0.05). TV/OCV ratio had a highly significant negative correlation with oral cavity airway volume (P &lt; 0.001). Conclusions These findings reflect the relationship of TV/OCV and their ratio on the upper airway especially in skeletal Class II malocclusions.

Repeated exposure to virtual reality decreases reliance on visual inputs for balance control in healthy adults

Postural control may encounter acute challenges when individuals are immersed in a virtual reality (VR) environment, making VR a potential pertinent tool for enhancing balance capacity. Nonetheless, the effects of repeated exposure to VR on balance control remain to be fully elucidated. Fifty-five healthy participants stood upright for six bouts of 90 s each in an immersive virtual reality (VR) environment using a head-mounted display (repeated VR exposure). During these bouts, participants experienced simulated forward and backward displacements. Before and after the repeated VR exposure, the center of pressure mean velocity (VELCOP) was measured in response to simulated forward and backward displacement in VR, as well as during quiet upright standing with eyes open (EO) and closed (EC) in the real environment. The results revealed a significant decrease in VELCOP for forward and backward simulated displacements in both antero-posterior and medio-lateral directions (p < 0.01) after compared to before repeated VR exposure. Furthermore, VELCOP significantly decreased when participants stood upright in EC (−5%; p = 0.004), but not EO (+3%; p > 0.05) in the real environment after repeated VR exposure. The Romberg ratio (EC/EO) was reduced in both antero-posterior and medio-lateral directions (p < 0.05) after VR exposure. This study indicates that repeated exposure to VR induces changes in balance control in both virtual and real environments. These changes may be attributed, in part, to a reduction in the weighting of visual inputs in the multisensory integration process occurring during upright standing. Accordingly, these findings highlight VR as a potentially effective tool for balance rehabilitation. Significance statementThis study indicates that repeated exposure to VR induces changes in balance control in both virtual and real environments that can rely, in part, on a reduction in the weighting of visual inputs in the multisensory integration process occurring during upright standing.

Numerical Analysis of Dynamic Response in Large Caissons during Wet-towing after Cable Breakage

Variable and complex marine environmental loads combined with wave resistance and the insufficient controllability of large caisson structures pose serious challenges during maritime towing. Cable breakage events are common, and improper behaviors could give rise to a variety of accidents. This work explored the dynamic responses of large caisson structures following towing cable breakage under irregular waves combined with harsh currents. Two types of cable breakage, i.e., main bridle and towing bridle breakage, were taken into account. Four potential wave–current combinations were assumed for each situation according to direction. The obtained results show that drag rope breakage could give rise to lateral shifts in the structure, which can become a serious condition when exposed to angled waves. Additionally, following breakage, significant force fluctuations took place in the remaining intact cables. For main cable breakage, both lateral and backward displacements were observed in the structure, which gradually entered a ‘flowing with the wave’ state. Furthermore, under the two abovementioned cable breakage conditions, the structure air gap consistently exceeded 2.3 m, ignoring the possibility of a wave slamming event.

Modeling and experimental evaluation of the stepping characteristic on a walking-type piezoelectric actuator

Aiming at the suppression of backward motion, a walking-type piezoelectric actuator was developed in this paper. Two walking modes of ellipse-shaped walking and rhombus-shaped walking were discussed. The dynamic models in the x and y direction were established to simulate the stepping characteristics of two walking modes. The simulated results depicted that the actuator was able to achieve stepping displacement free of backward motion. A prototype was fabricated, and a series of experiments were conducted. The experiments indicated that, under two walking modes, there was a backward displacement in each operating cycle due to assembly errors. To suppress backward motion, a solution to compensate for the assembly errors by varying the bias voltage difference between two stators was proposed. After correcting the assembly errors, the backward displacements were almost eliminated and reduced by 71.4% from 0.28 to 0.08 μm and 68.1% from 0.22 to 0.07 μm, respectively under the ellipse-shaped walking mode and rhombus-shaped walking mode, which proved the effectiveness of the proposed actuator.

Impact of prominence type on the coarticulation of vowels following palatalized consonants

The quantitative impact of prominence (neutral vs emphatic stress) on the coarticulation of the Russian low [æ], mid [e] and high [i] front vowels is evaluated in CV sequences with palatalized consonants of various places of obstruction. The research is conditioned by the aims of speech synthesis and recognition of the Russian language, the current data in the field being insufficient. First order linear equations (locus equations) are used to evaluate the degree of CV coarticulation. The experiment is performed on CjVCjV nonsense words imbedded in the middle position of a carrier phrase «Vyros CVCV sjyljnym» («CjVCjV has grown up strong»). The first syllable of the target words was uttered both with neutral and emphatic stress. The Praat software was used to measure F2 formant values at vowel onsets and central parts. It was established that linear regression slopes are similar both in the Y-intercepts and slope coefficients for the palatalized consonants of various places of obstruction uttered with the same prominence. The degree of coarticulation was different depending upon the type of prominence (neutral or emphatic): the coefficients were lower in case of the emphatic stress compared to those of the neutral one. ANOVA analysis and Student’s t-test were performed to reveal the difference in F2 values of vowel onsets and middle parts as a function of the vowel openness and type of prominence. The results obtained were interpreted based on the degree of the openness of the vowels under study: an open vowel under emphatic stress tends to expand its vowel space by a backward displacement while close vowels tend to move forward in the mouth cavity when pronounced with emphatic stress.

Keeping distance or getting closer: How others' emotions shape approach-avoidance postural behaviors and preferred interpersonal distance.

Understanding the influence of emotions on social interactions is important for a global understanding of the dynamics of human behavior. In this study, we investigated the interplay between emotions, spontaneous approach or avoidance tendencies, and the regulation of interpersonal distance. Fifty-seven healthy adults participated in a three-part experiment involving exposure to approaching or withdrawing emotional faces (neutral, happy, sad, fearful, disgusted, angry). The sequence began with an initial computerized stop-distance task, followed by a postural task in which participants' approach or avoidance tendencies were quantified via center of pressure (CoP-Y) displacements on a force platform, and concluded with a final computerized stop-distance task. Our findings revealed a gradient in postural responses, with the most forward CoP-Y displacements for neutral and happy faces, indicative of approach tendencies. These were followed by lesser forward displacements for sad and fearful faces, and most pronounced backward displacements for disgusted and angry faces, indicating avoidance. Furthermore, we observed modulations in participants' preferred interpersonal distance based on emotional cues, with neutral and happy faces associated with shorter distances, and disgusted and angry faces linked to larger distances. Despite these similar results, no direct correlation was found between CoP-Y and preferred interpersonal distance, underscoring a dissociation between spontaneous and voluntary social behaviors. These results contribute to a better understanding of how emotional expressions shape social interactions and underscore the importance of considering emotional cues, postural action tendencies, and interpersonal distance in facilitating successful social interactions.

Spinal alignment in habitual standing position and while using smartphones in healthy young adults

IntroductionA cascade of biomechanical changes occurs with postural deviations. Therefore, this study aimed to determine the trunk position and spine shape during smartphone use.MethodsBody posture was tested by the photogrammetric method in habitual standing position and while using smartphones in 39 healthy subjects of both sexes.ResultsWhile using smartphones, the trunk was shifted backwards (F(1.37) = 166.19, p = 0.0000), and the angle of the cervical spine increased in both sexes (p &lt; 0.05). Furthermore, the depth of thoracic kyphosis and lumbar lordosis increased (p &lt; 0.001), though only in the female group, but there were no differences in cervical load between groups (p &gt; 0.05).ConclusionsUsing a smartphone caused backward displacement of the upper torso in both sexes. It was also found that using a smartphone increased the depth of thoracic kyphosis and lumbar lordosis in females, which should be interpreted as a compensatory mechanism.

Optimizing the hydraulic performance of a baffled horizontal subsurface flow constructed wetland through computational fluid dynamics modelling

Baffled constructed wetlands (CWs) offer a promising solution to address low hydraulic efficiency in traditional CWs. However, there is a research gap in the field regarding the optimal length and quantity of baffles, and their comprehensive effects on hydraulic efficiency. This study is the first CFD-based assessment to comprehensively investigate the combined influence of baffle length and the number of baffles on the hydraulic efficiency of CWs. Using OpenFOAM simulations at a laboratory scale, various baffle configurations were examined with lengths ranging from 0.4 m to 0.58 m and baffle numbers varying from 0 to 11. Experimental tracer tests were conducted to validate the simulations. The high correlation coefficient (R2) between the tracer test results and simulations (ranging between 0.84 and 0.93) further underscores the reliability of the findings. Residence time distributions (RTDs) were derived from the temporal evolution of the outlet concentration of a tracer. The results indicate that augmenting the number of baffles under a fixed baffle length has a greater impact on the RTD curves, causing a backward displacement of the peak time. However, when the number of baffles is three or fewer, extending the baffle length does not significantly affect the RTD. When the baffle length is held constant at 0.58 m, there is a 58% enhancement in hydraulic efficiency as the number of baffles increases from 0 to 5. However, when maintaining a constant number of 11 baffles, increasing the baffle length from 0.4 to 0.5 m results in only a 5.5% improvement in hydraulic efficiency. Moreover, a generalized predictive equation for hydraulic efficiency was derived based on the CFD results and dimensional analysis. The study enhances the optimization of constructed wetland design by providing greater understanding of hydrodynamic behavior, leading to improved performance and applicability in practical environmental engineering.

The impact of femoral rotation on sacroiliac articulation during pregnancy. Is there evidence to support Farabeuf’s hypothesis by finite element modelization?

BackgroundCounter-nutation movement is deemed crucial during the management of the birth process. It is a combination of lateral ilia expansion and backward displacement of the promontory resulting from the external rotations of the femurs producing an enlargement of the pelvic inlet. However, since its description by Farabeuf, this mechanism has never been challenged and analyzed in a dynamic finite element study. MethodsBased on a female pelvic mesh and sacroiliac ligaments, we simulated external rotations of both femurs with imposed rotation of the two acetabulum centers. We hypothesize that lateral ilia expansion generates a sacrum movement resulting in a backward displacement of the promontory and a pelvic inlet enlargement. ResultsFinite element simulation confirms our hypothesis and reveals that ilio-sacro-transverse and axile ligaments play an essential role in this mechanism. Indeed, the increase in stiffness (ranging from 500 MPa to 750 MPa) of these ligaments accentuates the counter-nutation movement and the opening of the inlet. Instead of the anatomic congruence between the ilium and the sacrum, the sacroiliac ligaments may explain the counter-nutation. After a 6° of femur rotation, the inlet area increases to 11 cm2 (141 cm2 vs. 130 cm2). This enlargement could be noteworthy in case of obstructed labor or shoulder dystocia. Moreover, the association between external rotation and flexion of the femurs could be more efficient for opening the pelvic inlet. ConclusionsOur result did not support the original assumption of Farabeuf. By revealing how postural adjustment increases the bony birth canal, this study provides essential information for the clinical management of the delivery.

Finite element analysis of different reconstruction methods of coracoclavicular ligament for acromioclavicular joint dislocation

This study aims to examine the biomechanical effects of different reconstruction methods, including single-bundle, double-bundle anatomical reconstruction, and double-bundle truly anatomical reconstruction of the coracoclavicular ligament on the acromioclavicular joint using finite element analysis, to provide a theoretical basis for the clinical application of truly anatomical coracoclavicular ligament reconstruction. One volunteer, aged 27 years old, with a height of 178 cm and a weight of 75 kg, was selected for CT scanning of the shoulder joint. Three-dimensional finite element models of single-bundle reconstruction, double-bundle anatomical reconstruction, and double-bundle truly anatomical reconstruction of coracoclavicular ligament were established by using Mimics17.0, Geomagic studio 2012, UG NX 10.0, HyperMesh 14.0 and ABAQUS 6.14 software. The maximum displacement of the middle point of the distal clavicle in the main loading direction and the maximum equivalent stress of the reconstruction device under different loading conditions were recorded and compared. The maximum forward displacement and the maximum backward displacement of the middle point of the distal clavicle in the double-bundle truly anatomic reconstruction were the lowest, which were 7.76 mm and 7.27 mm respectively. When an upward load was applied, the maximum displacement of the distal clavicle midpoint in the double-beam anatomic reconstruction was the lowest, which was 5.12 mm. Applying three different loads forward, backward, and upward, the maximum equivalent stress of the reconstruction devices in the double-beam reconstruction was lower than that in the single-beam reconstruction. The maximum equivalent stress of the trapezoid ligament reconstruction device in the double-bundle truly anatomical reconstruction was lower than that in the double-bundle anatomical reconstruction, which was 73.29 MPa, but the maximum equivalent stress of the conoid ligament reconstruction device was higher than that of the double-bundle anatomical reconstruction. The truly anatomical reconstruction of coracoclavicular ligament can improve the horizontal stability of acromioclavicular joint and reduce the stress of the trapezoid ligament reconstruction device. It can be a good method for the treatment of acromioclavicular joint dislocation.

Evaluation of stresses and displacement in the craniofacial region as a reaction to bone-anchored maxillary protraction in conjugation with posterior bite plane and rapid maxillary expansion in patients with Class III malocclusion: A finite element analysis study

Treating a Class III malocclusion is often challenging for orthodontists. Bone-anchored maxillary protraction (BAMP) is known for achieving a significant maxillary protraction. The study aimed to evaluate the stress distribution and displacement of craniofacial bones as a reaction to the forces of BAMP, along with rapid maxillary expander and the posterior bite plane, in growing patients with skeletal Class III malocclusion using a finite element method. An finite element model was constructed from the spiral computed tomographic images of a skull from an 11-year-old growing patient with skeletal Class III malocclusion along with BAMP, rapid maxillary expander, and the posterior bite plane. The created model had 105,189 nodes and 481,066 elements. After assigning the appropriate material properties and the boundary condition, 800 g of transverse force per side and a Class III intraoral elastic 250 g of force per side were applied to the model, and after the postprocessing, the results were obtained in the form of color bands. The maxilla and the attached structures were displaced and expanded transversely. The maxilla was displaced anteriorly by 0.692 mm, and the mandible was displaced backward by 0.204 mm in the sagittal direction. The anterior region of the maxilla and mandible, dentition, and nasal bone were rotated counterclockwise. Displacement in an upward direction was greatest at the symphysis region of the mandible. The stresses experienced by most of the bones were tensile, with the maxilla and maxillary dentition experiencing the maximum. Favorable changes were appreciated with maxillary forward and mandibular backward displacement, with appreciable tensile stresses in all the bones.

Correlation between the ablation ratio and posterior corneal stability after small incision lenticule extraction for high myopia

PurposeThe aim of this study is to investigate changes in posterior corneal elevation and their correlations with the ablation ratio 3 years after small incision lenticule extraction (SMILE) for high myopia.MethodsEighty eyes underwent SMILE were enrolled in this study. Eyes were classified into two groups based on the ablation ratio (AR, lenticule thickness from SMILE machine/thinnest corneal thickness): group A (< 25%, 40 eyes) and group B (≥ 25%, 40 eyes). Pentacam was used to measure the posterior corneal elevation at the central point, thinnest point, and posterior maximum elevation (PME) and the mean posterior elevation in the central 2-mm area (MPE-2 mm), 4-mm area, and 6-mm area at the 3-year follow-up.ResultsMore than 85% of the eyes had an AR of less than 27%, and no cases of iatrogenic keratectasia developed. In both groups, for central region, posterior elevation decreased implying backward displacement; for peripheral region, it increased indicating forward trend. There was no significant difference in changes in all determined parameters between the two groups (P ≥ 0.07). Moreover, no significant correlation was noted between AR and posterior elevation changes. In group A, decreasing changes in PME (r = − 0.42, P = 0.01) and MPE-2 mm (r = 0.40, P = 0.01) demonstrated negative correlations with residual bed thickness.ConclusionRegion-dependent changes were demonstrated in the eyes that underwent SMILE. The central area showed a subtly declining posterior elevation, and the peripheral area showed a slightly increasing elevation. The limited ablation ratio had no impact on the changes in posterior corneal elevation.

Analysis of intraocular lens displacement relative to the haptic plane by ultrasound biomicroscopy data

This study analyzed cases with postoperative displacement of intraocular lens (IOL) relative to the haptic plane using ultrasound biomicroscopy (UBM). The study analyzed biometry data of 231 patients (277 eyes) aged 72.39±7.77 years, among them 43.25% were males. IOL position and refraction were analyzed at 1, 3 and 6 months after standard phacoemulsification. UBM was performed to analyze the position of the IOL. Stabilization of lens position was observed by the 3rd month of observation. Among the cases with displacement of the optical part relative to the haptic plane, the forward shift was determined in 24.85%, backward - in 16.67% of cases. Eyes with opposite IOL displacements differed significantly in lens diameter, ciliary sulcus diameter and the power of implanted IOL. IOL shift towards the retina produced significant hyperopic refractive error. A discriminant function was compiled using preoperative biometry data comprising the model for predicting backward IOL displacement with high probability. However, we failed to obtain a qualitative model for forward IOL displacements. Calculation error in modern formulas could occur because of IOL displacement, including the shift of the optical part relative to the haptic plane in postoperative period. Analysis of biometry data allows calculating IOL displacement towards the retina with a high probability, which could help avoid hyperopic refraction error postoperatively.

Effect of cervical spine motion on displacement of posterolateral annulus fibrosus in cervical spondylotic radiculopathy with contained posterolateral disc herniation: a three-dimensional finite element analysis

BackgroundPrevious studies on dynamic impingement of nerve root in cervical spondylotic radiculopathy (CSR) have focused on effect of cervical spine motion (CSM) on dimensional changes of intervertebral foramen. However, there are few studies to investigate effect of CSM on displacement of posterolateral intervertebral disc until now. The present study aimed to investigate effect of CSM on displacement of posterolateral annulus fibrosus (AF) in CSR with contained posterolateral disc herniation.MethodsA C5–C6 CSR finite element model with unilateral contained posterolateral disc herniation was generated based on validated C5–C6 normal finite element model. Forward and backward displacement distributions of posterolateral AFs in CSR model and normal model were compared. Changes in forward and backward displacement magnitudes of posterolateral AFs of the herniated side and the healthy side in CSR model, with respect to those of the ipsilateral posterolateral AFs in normal model, were compared. The comparisons were performed under flexion, extension, lateral bendings and axial rotations.ResultsThere was no difference in deformation trend of posterolateral AF between CSR model and normal model. Bilateral posterolateral AFs mainly moved forward during flexion and backward during extension. Left posterolateral AF mainly moved backward and right posterolateral AF forward during left lateral bending and left axial rotation. Left posterolateral AF mainly moved forward and right posterolateral AF backward during right lateral bending and right axial rotation. However, with respect to forward and backward displacement magnitudes of the ipsilateral posterolateral AFs in normal model, those of the herniated side increased relatively significantly compared with those of the healthy side in CSR model.ConclusionsFlexion, lateral bending to the healthy side and axial rotation to the healthy side make posterolateral AF of the herniated side mainly move forward, whereas extension, lateral bending to the herniated side and axial rotation to the herniated side make it mainly move backward. These data may help select CSM or positions to diagnose and treat CSR with contained posterolateral disc herniation. Increase in deformation amplitude of posterolateral AF of the herniated side may also be the reason for dynamic impingement of nerve root in CSR with contained posterolateral disc herniation.

Salinity and Temperature Variations near the Freshwater-Saltwater Interface in Coastal Aquifers Induced by Ocean Tides and Changes in Recharge

The temperature distribution of shallow sectors of coastal aquifers are highly influenced by the atmospheric temperature and recharge. However, geothermal heat or vertical fluxes due to the presence of the saline wedge have more influence at deeper locations. In this study, using numerical models that account for variable density, periodic oscillations of temperature have been detected, and their origin has been attributed to the influence exerted by recharge and tides. The combined analysis of field data and numerical models showed that the alternation of dry and wet periods modifies heat distribution in deep zones (&gt;100 m) of the aquifer. Oscillations with diurnal and semidiurnal frequencies have been detected for groundwater temperature, but they show differences in terms of amplitudes and delay with electrical conductivity (EC). The main driver of the temperature oscillations is the forward and backward displacement of the freshwater–saltwater interface, and the associated thermal plume generated by the upward flow from the aquifer basement. These oscillations are amplified at the interfaces between layers with different hydraulic conductivity, where thermal contours are affected by refraction.

Spin wave driven domain wall motion in easy-plane ferromagnets: A particle perspective

In easy-plane ferromagnets, we show that the interplay between a domain wall and a spin wave packet can be formulated as the collision of two massive particles with a gravitylike attraction. In the presence of magnetic dissipation, the domain wall mimics a particle subject to viscous friction, while the spin wave packet resembles a particle of variable mass. Due to the attractive nature of the interaction, the domain wall acquires a backward displacement as a spin wave packet penetrating the domain wall, even though there is no change in momentum of the wave packet before and after penetration.

Three-year clinical outcomes and posterior corneal elevation change after small-incision lenticule extraction in suspicious corneas.

To determine the long-term clinical outcomes and change in posterior corneal elevation after small-incision lenticule extraction (SMILE) in eyes with suspicious tomographic features. Hospital clinic. Retrospective, case-controlled, observational. This study included 43 patients with suspicious corneas (group A), defined by corneal morphology and a final D score from a Scheimpflug camera (Pentacam), and 43 patients with normal corneal topography (group B). Refraction, visual acuity, and posterior corneal elevation over a 6-mm central diameter, including posterior central elevation (PCE), posterior elevation at the thinnest point (PTE), and posterior maximal elevation (PME), were measured preoperatively and at 6 months, 12 months, and 36 months postoperatively. The preoperative spherical equivalent was -5.51 ± 1.33 D in group A (n = 43) and -5.41 ± 1.19 D in group B (n = 43). Postoperative uncorrected distance visual acuity was 20/20 or better in 39 (91%) of 43 eyes in group A and 41 (95%) of 43 eyes in group B ( P = .160); all eyes in both groups remained stable or had gained corrected distance visual acuity. The mean change in PCE, PTE, and PME at 3 years was -1.22 ± 2.65 μm, -1.21 ± 2.70 μm, and -1.00 ± 5.09 μmin group A and -1.76 ± 3.25 μm, -1.60 ± 3.33 μm, and -1.56 ± 5.01 μm in group B, respectively, indicating a tendency for backward displacement of the posterior surface, whereas the between-group difference was not statistically significant ( P = .154, P = .547, and P = .319, respectively). Refraction, visual outcomes, and posterior corneal shift seem comparable between corneas with normal and suspicious tomographic features three years after SMILE. More long-term studies are warranted to corroborate the findings of this study.