Lateral Shift Research Articles

Quantum Goos-Hänchen switch in graphene junctions

Goos-Hänchen (GH) shift, an interference phenomenon describing the lateral shift of the reflected beam along the interface during total internal reflection, has attracted great interests in the field of quantum transport in two-dimensional materials. In particular, the GH effect generates a novel pseudospin-dependent scattering effect in graphene, which in turn results in an conductance step in the bipolar junctions. Here, we reveal that a barrier region with effective barrier strength χ can greatly enrich the GH effect in graphene junctions. In contrast to the conventional case where the negative shift is allowed only in the p-n junction, the thin barrier enables both negative and positive spatial shifts in pIn and nIn junctions, where I represents the barrier region. More interestingly, the lowest channel degeneracy can be efficiently varied by tuning χ in both the symmetric pInIp and the asymmetric pnIp junctions, leading to a highly controllable switch that switches the conductance between and . These results advance the knowledge of GH effects in electronic materials and suggest experimental avenues for its observation and manipulation.

Barcode encryption based on spin hall effect in tunable vertical hyperbolic metamaterial

In this work, we present a novel vertically hyperbolic metamaterial vHMM structure comprising multilayer stacks of titanium nitride TiN-alumina Al2O3 films. Based on the modulation of the parallel permittivity ɛ∥ and vertical permittivity ɛ⊥ of the vHMM structure by the filling ratio of TiN in the vHMM structure and incident wavelength, we theoretically design and analyze three epsilon-near-zero ENZ structures to investigate the spin Hall effect of light SHEL. Our results demonstrate that all three ENZ structures exhibit significant enhancement of SHEL, with the lateral shift exhibiting extreme sensitivity to the incident angle and producing micron-level variations within a few milliradians. Notably, the class-II of ENZ structure ɛ∥≠0,ɛ⊥≈0 suffers from the highest loss and yields the weakest enhancement of SHEL. Furthermore, we discover that the sign of the transverse shift of the SHEL can also be modulated according to the filling ratio of TiN in the vHMM structure and incident wavelength within a specific incident angle. Based on the regulation law, we propose two barcode encryption schemes that exploit the traverse directions. Our study provides a new mechanism for practical applications of SHEL in optical communication and data storage.

Fatigue task-dependent effect on spatial distribution of lumbar muscles activity

This study aims to identify how spatial distribution of lumbar muscle activity is modulated by different fatigue tasks. Twenty healthy adults performed two different isometric trunk extension endurance tasks (the modified Sorensen test and the inverted modified Sorensen test) until exhaustion. During these tasks, bilateral superficial lumbar muscle activity was recorded using high-density electromyography. The spatial distribution of activation within these muscles was obtained using the centroid coordinates in the medio-lateral and cranio-caudal directions. The effects of task and endurance time (left and right sides) were investigated using repeated measures ANOVA. Results revealed a significant lateral shift of the centroid throughout the fatigue tasks on both sides and no difference between tasks. Significant task × time interaction effects were found for the cranio-caudal direction on both sides showing a significantly more caudal location of the centroid in the modified Sorensen test compared to the inverted test at the beginning of the tasks. Our findings suggest that spatial distribution of lumbar muscle activity is task-dependent in a pre-fatigue stage while an alternative but similar muscle recruitment strategy is used in both tasks to maintain performance in the later stages of muscle fatigue.

Measuring highly accurate foot position and angle trajectories with foot-mounted IMUs in clinical practice

BackgroundGait analysis using foot-mounted IMUs is a promising method to acquire gait parameters outside of laboratory settings and in everyday clinical practice. However, the need for precise sensor attachment or calibration, the requirement of environments with a homogeneous magnetic field, and the limited applicability to pathological gait patterns still pose challenges. Furthermore, in previously published work, the measurement accuracy of such systems is often only validated for specific points in time or in a single plane. Research questionThis study investigates the measurement accuracy of a gait analysis method based on foot-mounted IMUs in the acquisition of the foot motion, i.e., position and angle trajectories of the foot in the sagittal, frontal, and transversal plane over the entire gait cycle. ResultsA comparison of the proposed method with an optical motion capture system showed an average RMSE of 0.67° for pitch, 0.63° for roll and 1.17° for yaw. For position trajectories, an average RMSE of 0.51 cm for vertical lift and 0.34 cm for lateral shift was found. The measurement error of the IMU-based method is found to be much smaller than the deviations caused by the shoes. SignificanceThe proposed method is found to be sufficiently accurate for clinical practice. It does not require precise mounting, special calibration movements, or magnetometer data, and shows no difference in measurement accuracy between normal and pathological gait. Therefore, it provides an easy-to-use alternative to optical motion capture and facilitates gait analysis independent of laboratory settings.

Mapping the Cortical Representation of Paraspinal Muscles Using Transcranial Magnetic Stimulation Optimized in People With Chronic Back Pain.

Chronic low back pain (CLBP) is a global burden with an unknown etiology. Reorganization of the cortical representation of paraspinal muscles in the primary motor cortex (M1) may be related to the pathology. Single-pulse transcranial magnetic stimulation (TMS), commonly used to map the functional organization of M1, is not potent enough to stimulate the cortical maps of paraspinal muscles in M1 in CLBP patients with reduced corticospinal excitability (CSE) with intensities even as high as maximum stimulator output (100% MSO). This makes TMS mapping impractical for these patients. The aim of this study was to increase the practicality of TMS mapping for people with CLBP. This study included eight men and ten women who had CLBP for over three months. A biphasic paired-pulse TMS paradigm, conjunct anticipatory postural adjustment (APA), and maximal voluntary activation of paraspinal muscles (MVC) were used to facilitate TMS mapping. TMS mapping was possible in all CLBP participants, with TMS intensities <50% of the MSO. Reorganization in terms of an anterior and lateral shift of the center of gravity (COG) of the cortical maps of paraspinal muscles was observed in all participants with CLBP, and a reduced number of discrete peaks was found in 33%. The facilitation of the CSE to paraspinal muscles makes TMS mapping more practical and tolerable in people with CLBP, lowering the risk of seizure and discomfort associated with high-intensity TMS pulses. Conventional transcranial magnetic stimulation (TMS) brain mapping is not optimal for patients with Chronic low back pain (CLBP).Paired-pulse TMS dramatically lessens the energy needed for brain mapping.Maximal voluntary contraction of back muscles facilitates TMS mapping.Anticipatory postural activity of back muscles enhances the efficacy of TMS mapping. Chronic low back pain (CLBP) is a social, emotional, and economic burden and the leading cause of disability worldwide. Yet the etiology of the CLBP is unknown. The persistence of aberrant or antalgic movement patterns observed in people with CLBP has been suggested as a possible cause of pain chronification by inducing continuous damage to sensitive structures of the lumbar spine. It is well known that the brain is in charge of the production and planning of movements, so it is likely that abnormal movement patterns also stem from the abnormalities in the brain. However, until recently, human knowledge about the structure and function of the brain has been very limited. The invention of noninvasive and painless brain imaging and stimulating techniques such as transcranial magnetic stimulation (TMS) during the last decades has augmented our knowledge about the structure and function of the brain. Modification in terms of shift, shrinkage, or expansion of areas of the brain devoted to movement control or sensation of the back muscles has been documented in CLBP via these techniques, which are argued to relate to pain chronification but need further clarification. Yet monitoring the course of CLBP via TMS, despite its many potentials, is challenging. This could be due to the reduced cortical drive to back muscles in CLBP patients and the small area devoted to control of back muscles in the brain in general that increases the brain threshold to TMS in people with CLBP. The aim of this study was to tailor an approach to make TMS more applicable for CLBP patients by reducing the threshold to TMS. This could be achieved by engaging back muscles in anticipatory postural activity in combination with maximal voluntary activation of these muscles, along with TMS paradigms that induce intracortical facilitation.

Model for Predicting Lateral Shifts and Driving Style of Motorized Two-Wheelers

The compact sizes, lack of available physical protection, and complex maneuvering patterns of motorized two-wheeler (MTW) riders make them more vulnerable to crash risks and accidents. Considering the increased vulnerability of MTWs in dense urban mixed traffic environments, a proper evaluation and modeling of their lateral movement decisions and driving style can enhance safety associated with the riders and augment the reliability of the existing microsimulation models. Utilizing trajectory data of a six-lane divided urban arterial, the current study attempts to investigate the lateral movement (lateral shift) tendency of MTWs, addressing different influential variables that may affect riders’ decisions and describing how this choice is affected by prevailing traffic conditions. Based on several driving style parameters, such as change in speed, change in angular position, and longitudinal gap maintained with rear vehicles, this study further contributes to the existing literature by proposing a new index for identifying the driving style of riders during the lateral shifting process. Modeling results of a multinomial logit model indicated the importance of considering longitudinal and lateral gaps, vehicle speeds, and lateral fluctuations made by the subject MTW in the past trajectories in modeling the lateral shift decisions of riders. Considering the number of lateral fluctuations as an indicator of MTWs’ driving style, a new “aggressiveness index” is defined and, accordingly, a modeling approach is proposed to classify aggressive and non-aggressive driving styles of the riders. The results suggest that the history of past trajectories of the subject MTW during lateral shifting should be considered, and consideration of a non-linear relationship among the parameters can result in a better classification of driving style of MTW riders.

Study of Transversely Isotropic Visco-Beam with Memory-Dependent Derivative

Based on the modified Moore–Gibson–Thompson (MGT) model, transversely isotropic visco-thermoelastic material is investigated for frequency shift and thermoelastic damping. The Green–Naghdi (GN) III theory of thermoelasticity with two temperatures is used to express the equations that govern heat conduction in deformable bodies based on the difference between conductive and dynamic temperature acceleration. A mathematical model for a simply supported scale beam is formed in a closed form using Euler Bernoulli (EB) beam theory. We have figured out the lateral deflection, conductive temperature, frequency shift, and thermoelastic damping. To calculate the numerical values of various physical quantities, a MATLAB program has been developed. Graphical representations of the memory-dependent derivative’s influence have been made.

Modelling and Analysis of Dynamic Servo Error of Heavy Vertical Machining Centre Considering Nonlinear Factors

The dynamic servo error of heavy-duty vertical machining centres is one of the decisive factors affecting the machining accuracy of large and complex parts. Due to the characteristics of large mass, large load, and the large travel distance of the machine tool, non-linear factors such as friction, backlash, and lateral shift are more likely to cause unstable behaviours such as stick-slip and oscillation of the servo feed system of the machine tool, and reduce the performance and servo accuracy of the motion axis. In this paper, to consider the influence of non-linear factors such as friction, backlash, and lateral shift, an appropriately simplified representation of the mechanical transmission system of the ball screw has been used. According to the control structure of the Siemens 840D numerical control system, a theoretical model of the servo feed system for the heavy-duty vertical machining centre was established based on three-loop control. Then, the single-axis and double-axis closed-loop simulation models of the servo feed system were built in Simulink, and the influence pattern of control parameters and nonlinear factors on the dynamic servo error was obtained through simulation analysis. Finally, the validity of the theoretical model for the servo feed system was verified through a comprehensive comparison of simulation and experimental outcomes. This encompasses an analysis of the control system Bode plots, critical stick-slip velocity, and tracking errors in the X-axis with linear motion. The validation provides theoretical guidance for parameter design and mechanical adjustments of the servo feed system in heavy-duty vertical machining centres.

Warming and lateral shift of the Gulf Stream from in situ observations since 2001

Warming and lateral shift of the Gulf Stream from in situ observations since 2001

Shape analysis of the preorbital bar in caviomorph rodents.

The highly specialised masticatory apparatus of rodents raises interesting questions about how their skull withstands the intensive and sustained forces produced by biting on hard items. In these mammals, major systematics were explored for a long time based on the adductor muscles' architecture and the related bony structures. The infraorbital foramen stands out, where a hypertrophied head of the zygomaticomandibular muscle passes through-in hystricomorphous rodents-as a direct consequence of the lateral and posterior shift of the preorbital bar. Interestingly, this bar moved laterally and backwards-enlarging the foramen-but it never disappeared throughout evolution, even showing morphological convergence among rodents. Previous research proposed this bar as behaving mechanically similar to the postorbital bar in ungulates, i.e., a safety structure against torsion stress while chewing. We analysed its morphology by mathematically modelling it under bending and torsion scenarios (linearly and elliptically shaped, respectively), and as for biting load propagation (catenary curve). Although the preorbital bar primarily seems to be shaped for withstanding torsional stress (as the postorbital bar in ungulates) and as an escaping point for force propagation, these forces are not a consequence of chewing and grinding foods, but preventing the zygomatic arch from failing when the powerful laterally-displaced jaw adductor muscles are pulling the dentary upwards at biting.

Supramalleolar Osteotomy Combined with Medial Malleolar Osteotomy for Varus Ankle Osteoarthritis with Varus Medial Malleolar Deformity

Category: Ankle Arthritis; Ankle Introduction/Purpose: In some cases of varus ankle osteoarthritis (VAO), the varus medial malleolar deformity causes widening of the mortise and reduced conformity. In such cases, the angles of the medial distal tibial platform and the angle of the talar medial shoulder are different, so it is necessary to match the angles of both to improve the compatibility of the mortise. We performed lateral closing wedge supramalleolar osteotomy (LCWSMO) with opening wedge medial malleolar osteotomy (OWMMO) to achieve lateral shift of the load-bearing axis and mortise-plasty at the same time. The purpose of this study was to evaluate the therapeutic outcomes of this technique for VAO with the varus medial malleolar deformity. Methods: The subjects were 12 joints in 12 cases, two males and ten females, the mean age at the surgery was 58.2 years (36-76 years), and the mean follow-up period was 9 years and 1 month (1-20 years and 4 months). After LCWSMO was performed, OWMMO was made to fit the mortise, and autogenous bone grafting was performed in the gap. Additional surgery included two lateral ligament reconstructions, one osteochondral graft, and one high tibial osteotomy. Clinical evaluation was performed using the score of Takakura et al. For arthroscopic evaluation, we used our five grades classification, which is based on the percentage of eburnation areas on the articular surface. The radiographic assessments were the Takakura-Tanaka staging system, the tibial articular surface angle, the tibial lateral surface angle, the talar tilting angle, and the ratio of the medial distal tibial platform angle to the medial talar shoulder angle. Results: The clinical score improved from a preoperative average of 65.0±9.3 points to 82.8±9.8 points at the final follow-up. All arthroscopic grade improved at one year after surgery except one each of grade 2 and grade 3 joints which remained unchanged. According to the postoperative radiographic staging, 6 joints had improved, 3 had not changed, and 3 had progressed. The tibial articular surface angle increased from an average of 84.4 ± 2.1° preoperatively to 97.4 ± 3.6° at the last observation, the tibial lateral surface angle from 80.5 ± 2.5° to 83.7 ± 5.9°, the talar tilting angle increased 11.3 ± 4.7° to 7.9 ± 4.3°, and the ratio of the medial distal tibial platform angle to the medial talar shoulder angle from 112.3±4.9% to 103.6±5.8%. Conclusion: For VAO with varus medial malleolar deformity and large mortise opening, good results can be obtained by lateral shift the load-bearing axis with LCWSMO and improving the fit of the mortise with OWMMO.

The Density-Weighted Foot Center Is Different to the Geometric Foot Center

Category: Basic Sciences/Biologics; Hindfoot Introduction/Purpose: It has become a reality with the advent of weight bearing CT (WBCT) that weight bearing (WB) is a significant element to be considered when analyzing foot and ankle images. Some knowledge has begun to accumulate on the effect of WB on bone positioning, but the effect of WB on bone mineral density (BMD) distribution, apart from being a long for accepted truth since the works of Julius Wolff, could not until now be visualized other than on the biological level. Now, Hounsfield Units allow for bone density analysis on WBCT. The objective of the study was to compare the relative positions of the geometric foot center (GC) and the density-weighted foot center (DC). We hypothesized those to be different. Methods: Ethics approval was obtained. Thrity two feet from our WBCT database were retrospectively randomly selected (Curvebeam Pedcat, Hatfield PA, USA). Datasets were analyzed using Bonelogics software (Disior, Paragon 28, USA). Bone segmentation was performed to obtain all bone orientations and volumes excluding tibia and fibula and all phalanges. The data was computed to obtain the geometric centers (from bone surface coordinates), which were considered as reference and were given a value of 0. Therefore density-weighted centers (from all bone data including density) were calculated. The difference between the two centers represented the shift which was assessed along the sagittal axis (anterior shift), transversal axis (lateral shift) and craniocaudal axis (upward shift). Statistical analysis was conducted using STATA package. Results: The mean age and Body Mass Index of the cohort were 57.2 ± 9.6 years and 22.2 ± 2.8 kg/m2, respectively. The 3D displacement vector between GC and DC had a norm of 10.01 mm. We found that DC was significantly shifted anteriorly by 8.9 ± 0.3 mm (range, 5.6 mm to 13.4 mm), medially by 0.4 ± 0.8 mm (range, -1.3 mm to 0.3 mm) and upwardly by 4.2 ± 0.14 mm (range, 2.8 mm to 5.9 mm) (p &lt; 0.001 in all cases). Conclusion: Our hypothesis was confirmed: the geometric and weighed foot centers were different. DC was more anteriorly and slightly medially situated. Both centers were situated at the interface between the talus and cuboid. The more anterior position may be explained by the fact that human foot is responsible for anteriorly orientated longitudinal movement on average. We deem that BMD is a significant dimension in WBCT datasets that cannot be ignored in the development of new measurement tools that are not currently standardized. Alignment based purely on bone outer shape without considering BMD may not be representative of their true biomechanical state.

Changes in Coronal and Sagittal Alignment of the Ankle Joint After High Tibial Osteotomy: Evaluation Using Low Extremity Scanogram and EOS Imaging System

Category: Ankle; Hindfoot Introduction/Purpose: High tibial osteotomy (HTO) is a useful treatment option for symptomatic knee patients with varus knee alignment and medial compartment arthritis. Changes in coronal and sagittal alignment of the knee joint have been reported in several previous studies. However, no study have investigated the changes of both coronal and sagittal alignment of the ankle joint after HTO. The purpose of this study was to investigate changes in coronal and sagittal alignment of the ankle joint after HTO. Our hypothesis was that alignment of ankle joint, as well as knee joint, change significantly after HTO. Methods: Total 46 patients (49 cases) were retrospectively analyzed after HTO for varus knee osteoarthritis. Preoperative and follow-up of low extremity scanogram and EOS imaging system were taken. The hip–knee–ankle (HKA) angle, medial proximal tibial angle (MPTA), knee tibia plafond angle (KTPA), were measured by scanogram to evaluate coronal alignment of the knee. Tibial anterior surface angle (TAS), Tibial plafond inclination (TPI), talar tilt (TT), and ankle joint axis point on the weight-bearing- line (AAWBL) were measured by scanogram to investigate coronal alignment of the ankle. Tibial lateral surface angle (TLS) and lateral knee tibial plafond angle (LKTPA) were measured by EOS to evaluate sagittal alignment of the ankle. Radiologic outcomes of the knee and ankle were evaluated pre- and postoperatively. Results: Varus alignment of the knee was corrected by significant coronal change of the HKA angle, MPTA, KTPA after HTO (P &lt; 0.05). There was significant coronal change in TPI and AAWBL in ankle alignment (P &lt; 0.05). The ankle joint axis point on the weightbearing axis moved laterally which was demonstrated by AAWBL. However, there was no significant difference between preoperative and follow up TAS and TT (P &gt; 0.05). In sagittal alignment of ankle by EOS, LKTPA significantly increased after HTO (P &gt; 0.05), but TLS showed no significant difference postoperatively (P &gt; 0.05). Conclusion: Coronal and sagittal alignment of ankle joint was significantly changed after HTO by lateral shift of ankle joint axis and LKTPA increase after HTO. Further study is necessary to investigate the effects of the present radiologic results on clinical symptoms of the patients.

A fast analytical dose calculation approach for MRI-guided proton therapy.

Objective.Magnetic resonance (MR) is an innovative technology for online image guidance in conventional radiotherapy and is also starting to be considered for proton therapy as well. For MR-guided therapy, particularly for online plan adaptations, fast dose calculation is essential. Monte Carlo (MC) simulations, however, which are considered the gold standard for proton dose calculations, are very time-consuming. To address the need for an efficient dose calculation approach for MRI-guided proton therapy, we have developed a fast GPU-based modification of an analytical dose calculation algorithm incorporating beam deflections caused by magnetic fields.Approach.Proton beams (70-229 MeV) in orthogonal magnetic fields (0.5/1.5 T) were simulated using TOPAS-MC and central beam trajectories were extracted to generate look-up tables (LUTs) of incremental rotation angles as a function of water-equivalent depth. Beam trajectories are then reconstructed using these LUTs for the modified ray casting dose calculation. The algorithm was validated against MC in water, different materials and for four example patient cases, whereby it has also been fully incorporated into a treatment plan optimisation regime.Main results.Excellent agreement between analytical and MC dose distributions could be observed with sub-millimetre range deviations and differences in lateral shifts <2 mm even for high densities (1000 HU). 2%/2 mm gamma pass rates were comparable to the 0 T scenario and above 94.5% apart for the lung case. Further, comparable treatment plan quality could be achieved regardless of magnetic field strength.Significance.A new method for accurate and fast proton dose calculation in magnetic fields has been developed and successfully implemented for treatment plan optimisation.

Effect of an inter-vehicle damper on the dynamics of a high-speed train

It is meaningful to understand the effect of inter-vehicle damper and its parameters on high-speed train dynamics in the context of train inter-vehicle suspension design or optimization. In this study, Multi-body System (MBS) dynamics modelling of a high-speed CRH train with inter-vehicle damper is firstly carried out, in which a simplified-parametric model was proposed and validated to depict damping characteristics of the damper. Simulation results using the MBS model show that inter-vehicle damper devised in high-speed train can obviously reduce lateral vibrations at the connecting passage of adjacent compartments without increasing the wheelset lateral shift force and derailment coefficient, thus it can improve overal ride comfort of the CRH train. In addition, inter-vehicle damper can resist severe lateral shocks and guarantee safety when two high-speed trains pass each other. The developed MBS model of the CRH train is an accurate and useful platform, the obtained results in this study are also valuable in following vibration analysis and inter-vehicle suspension optimization of the CRH train.

A scintillation dosimeter with real-time positional tracking information for in vivo dosimetry error detection in HDR brachytherapy.

To evaluate the performance of an electromagnetic (EM)-tracked scintillation dosimeter in detecting source positional errors of IVD in HDR brachytherapy treatment. Two different scintillator dosimeter prototypes were coupled to 5 degrees-of-freedom (DOF) EM sensors read by an Aurora V3 system. The scintillators used were a 0.3 × 0.4 × 0.4 mm3 ZnSe:O and a BCF-60 plastic scintillator of 0.5 mm diameter and 2.0 mm in length (Saint-Gobain Crystals). The sensors were placed at the dosimeter's tip at 20.0 mm from the scintillator. The EM sampling rate was 40/s while the scintillator signal was sampled at 100 000/s using two photomultiplier tubes from Hamamatsu (series H10722) connected to a data acquisition board. A high-pass filter and a low-pass filter were used to separate the light signal into two different channels. All measurements were performed with an afterloader unit (Flexitron-Elekta AB, Sweden) in full-scattered (TG43) conditions. EM tracking was further used to provide distance/angle-dependent energy correction for the ZnSe:O inorganic scintillator. For the error detection part, lateral shifts of 0.5 to 3 mm were induced by moving the source away from its planned position. Indexer length (longitudinal) errors between 0.5 to 10 mm were also introduced. The measured dose rate difference was converted to a shift distance, with and without using the positional information from the EMsensor. The inorganic scintillator had both a signal-to-noise-ratio (SNR) and signal-to-background-ratio (SBR) close to 70 times higher than those of the plastic scintillator. The mean absolute difference from the dose measurement to the dose calculated with TG-43U1 was 1.5% ±0.7%. The mean absolute error for BCF-60 detector was 1.7% when compared to TG-43 calculations formalism. With the inorganic scintillator and EM tracking, a maximum area under the curve (AUC) gain of 24.0% was obtained for a 0.5-mm lateral shift when using the EMT data with the ZnSe:O. Lower AUC gains were obtained for a 3-mm lateral shifts with both scintillators. For the plastic scintillator, the highest gain from using EM tracking information occurred for a 0.5-mm lateral shift at 20 mm from the source. The maximal gain (17.4%) for longitudinal errors was found at the smallest shifts (0.5 mm). This work demonstrates that integrating EM tracking to in vivo scintillation dosimeters enables the detection of smaller shifts, by decreasing the dosimeter positioning uncertainty. It also serves to perform position-dependent energy correction for the inorganic scintillator,providing better SNR and SBR, allowing detection of errors at greater distances from thesource.

Uncertainty-aware spot rejection rate as quality metric for proton therapy using a digital tracking calorimeter

Objective. Proton therapy is highly sensitive to range uncertainties due to the nature of the dose deposition of charged particles. To ensure treatment quality, range verification methods can be used to verify that the individual spots in a pencil beam scanning treatment fraction match the treatment plan. This study introduces a novel metric for proton therapy quality control based on uncertainties in range verification of individual spots. Approach. We employ uncertainty-aware deep neural networks to predict the Bragg peak depth in an anthropomorphic phantom based on secondary charged particle detection in a silicon pixel telescope designed for proton computed tomography. The subsequently predicted Bragg peak positions, along with their uncertainties, are compared to the treatment plan, rejecting spots which are predicted to be outside the 95% confidence interval. The such-produced spot rejection rate presents a metric for the quality of the treatment fraction. Main results. The introduced spot rejection rate metric is shown to be well-defined for range predictors with well-calibrated uncertainties. Using this method, treatment errors in the form of lateral shifts can be detected down to 1 mm after around 1400 treated spots with spot intensities of 1 × 107 protons. The range verification model used in this metric predicts the Bragg peak depth to a mean absolute error of 1.107 ± 0.015 mm. Significance. Uncertainty-aware machine learning has potential applications in proton therapy quality control. This work presents the foundation for future developments in this area.

Achromatic diffractive liquid-crystal optics for virtual reality displays

Diffractive liquid-crystal optics is a promising optical element for virtual reality (VR) and mixed reality as it provides an ultrathin formfactor and lightweight for human factors and ergonomics. However, its severe chromatic aberrations impose a big challenge for full-color display applications. In this study, we demonstrate an achromatic diffractive liquid-crystal device to overcome this longstanding chromatic aberration issue. The proposed device consists of three stacked diffractive liquid crystal optical elements with specifically designed spectral response and polarization selectivity. The concept is validated by both simulations and experiments. Our experimental results show a significant improvement in imaging performance with two types of light engines: a laser projector and an organic light-emitting diode display panel. In addition, our simulation results indicate that the lateral color shift is reduced by ~100 times in comparison with conventional broadband diffractive liquid-crystal lens. Potential applications for VR-enabled metaverse, spatial computing, and digital twins that have found widespread applications in smart tourism, smart education, smart healthcare, smart manufacturing, and smart construction are foreseeable.

The cerebellopontine angle cistern volumetric differences in trigeminal neuralgia patients with and without vertebrobasilar compression: a case-matched study.

Previous studies have indicated that the small cerebellopontine angle (CPA) cistern plays a role in the pathogenesis of trigeminal neuralgia (TN), but they are likely not involved in TN associated with vertebrobasilar artery (VBA) compression because of its rarity. Forty-four patients with VBA-associated TN and 44 age-, sex-, and hypertension-matched TN patients without VBA compression (non-VBA-associated) were included. All patients underwent high-resolution MRI. The CPA cistern volumes were measured bilaterally. The presence of vertebrobasilar dolichoectasia (VBD) and laterality of the vertebrobasilar junction (VBJ) were observed. The CPA cistern volume on the affected side was smaller than the unaffected side (714.4 ± 372.8 vs 890.2 ± 462.2 mm3, p < 0.001) in non-VBA-associated TN patients, while VBA-associated TN patients show a larger CPA cistern on the affected side than the unffected side (1107.0 ± 500.5 vs 845.3 ± 314.8 mm3, p < 0.001). The prevalence of VBD was higher in patients with VBA-associated TN than in matched non-VBA-associated TN patients (90.9% vs 4.5%, p < 0.001). A positive correlation between the laterality of VBJ and the affected side was found in the VBA-associated TN group (p < 0.0001). Large CPA cistern may be a neuroradiological feature of VBA-associated TN, and most of the VBA-associated TN is accompanied by VBD. The presence of VBD and the lateral shift of VBJ may expand the CPA cistern by squeezing the surrounding tissue on the affected side and also increase the chance of VBA compression on the trigeminal nerve, resulting in the genesis of VBA-associated TN.

A phase-field study of the peritectic reaction mechanisms in Fe-Ni alloys

A quantitative multi-phase field model is used to simulate the peritectic reaction in Fe-Ni alloys at low undercoolings. During the peritectic reaction, the concentration field and growing contour of the γ-phase are utilized to examine the morphological evolution. Numerical simulations indicate that the peritectic reaction contains complex mechanisms that include the remelting of δ-ferrite, the mixing of solutes in the liquid phase, and solute diffusion. It is found that the δ-ferrite remelts near the tip of the advancing γ-platelet during the steady-state peritectic reaction, resulting in the lateral shift of the triple junction. The remelting of δ-ferrite and subsequent solidification of the remelted liquid can contribute to rapid solute mixing in the liquid adjacent to the triple junction and considerably accelerate the growth rate of γ-platelet. The lateral shift of the triple junction can be employed to characterize the simulated morphology of the advancing γ-platelet tip during the Fe-Ni peritectic reaction. A novel Péclet number based on the lateral shift is introduced to quantify the rate of remelting of the δ-ferrite and its impact on the peritectic reaction. The diffusion-controlled mechanism is investigated by the scaling relations between the dimensionless undercooling and the steady-state tip properties, such as the reaction velocity, lateral shift, selection parameter, and Péclet number. The remelting rate of the δ-ferrite, characterized by the new Péclet number for the peritectic reaction, has a major impact on the diffusion-controlled mechanism. The differences in the peritectic morphology of Fe-Ni and Fe-C alloys have been confirmed by comparing the multi-phase field simulations with in-situ investigations. The correlation between the simulated γ-platelet thickness and the in-situ experiment data is considered to be satisfactory.