Mean Displacement Research Articles

Experimental Analysis of the Discharge Valve Movement of the Oil-Free Linear Compressor in the Refrigeration System

In a linear compressor, the valve motion significantly affects the thermodynamic efficiency and the compressor’s reliability, especially in oil-free conditions. To better understand the dynamic behavior of the discharge valve, a real-time test bench was built. The piston movements and dynamic pressure in the cylinder were also observed to obtain the synchronizing characteristics among the reed valve motion, cylinder pressure, and piston motion. Observing the motion of the discharge valve visually, the discharge valve flutters due to the change in the form of the cylinder pressure, the delayed opening of the valve is caused by the inertia of the valve itself, and additional displacement fluctuations are present. This paper presents the dynamic behavior of the discharge valve under different discharge pressure/operating frequency/piston stroke/clearance length conditions. The results show that the valve flutters increase, the mean displacement of the valve increases, and the duration of the discharge increases when the discharge pressure decreases. When the operating frequency increases, the duration of the discharge decreases, while the mean displacement of the valve increases. For a high stroke or a low clearance length case, the duration of the discharge increases, while the valve flutters increase due to the pressure fluctuations in the cylinder. Through analyzing the synchronizing characteristic among the valve movements, piston movements, and cylinder pressure, it is shown that the phenomenon of the delayed opening valve is much worse for a low stroke or a high operating frequency case. In addition, the delayed closing of the valve appears for a high operating frequency case (75 Hz).

Intra- and inter-individual variability in the underwater pull-out technique in 200 m breaststroke turns.

The purpose of the present study was to investigate the intra- and inter-individual variability in arm-leg coordination during the underwater phase of the turn segment in 200 m breaststroke. Thirteen male swimmers were recruited and performed a 200 m breaststroke in a pre-calibrated 25 m pool. Sub-phases during the underwater segment were obtained using a notational analysis, and the mean velocity, displacement and duration during each sub-phase were obtained. A hierarchical cluster analysis (HCA) was performed using the analysed variables in all phases to identify inter-individual variability and random intra-individual variability. In addition, a linear mixed model (LMM: lap as a fixed effect and the participant as a random effect) was conducted to investigate systematic intra-individual variability. HCA identified three coordination patterns that were distinguished by the timing of the dolphin kick relative to the arm pull-out and the duration of the glide with arms at the side. All swimmers except one performed the arm pull-out after the dolphin kick. Nine swimmers maintained one coordination pattern, but other swimmers switched their coordination during the trial, particularly by shortening the duration of the glide with arms at the side. LMM showed a linear decrease (from the first to the last turn) in the time gap between the end of the dolphin kick and the start of the arm pull-out (a glide with the streamlined body position; F = 9.64, p = 0.034) and the glide duration with the arms at the side (F = 11.66, p = 0.015). In conclusion, both inter- and intra-individual variabilities during the underwater phase were evident in 200 m breaststroke turns, which were categorised into three patterns based on the timing of the dolphin kick and the duration of glides.

Testing of a Novel Method for Securing Ligaments Against Bone During Simultaneous Medial and Lateral Elbow Ligament Reconstruction

A ligament reconstruction method that simultaneously tensions the medial and lateral sides of the elbow and maintains tension with compression plates on the proximal ulna is proposed for the treatment of bidirectional elbow ligament instability. Graft slippage, catastrophic failure, and excessive displacement were evaluated. Biomechanical stability without graft slippage was hypothesized. Eight cadaveric ligament reconstruction simulations were created through the dissection of three cadaver arms. Each reconstruction was statically tested with 160 N in a manner where it was first augmented with an absorbable suture and then without. Then, 3 more ligament reconstruction simulations were created for dynamic testing with each undergoing testing at 80 N for 2,000 cycles at 2 Hz. Construct displacement and graft slippage were recorded for each load application. No grafts failed catastrophically and no graft slippage was observed with either static or dynamic loading. Under static loading, the mean change in displacement between augmented and nonaugmented ligament reconstruction simulations was 28.7% ± 21% (augmented 3.95 ± 1.81 mm vs nonaugmented 4.89 ± 2.22 mm). The mean stiffness was 66.6 ± 26.6 N/mm for augmented and 64.6 ± 23.2 N/mm for nonaugmented simulations. With dynamic loading, the mean displacement for augmented graft ligament reconstruction simulations was 1.55 ± 0.16 mm compared with 2.18 ± 0.77 mm for nonaugmented reconstruction simulations. This method of fixation to the proximal ulna for the simultaneous reconstruction of medial and lateral elbow ligaments successfully prevented graft slippage without excessive construct displacement during static and dynamic testing. Ligament augmentation with absorbable sutures decreased the construct displacement. This ligament fixation method may be a viable alternative for the treatment of concomitant medial and lateral elbow instability.

Drag reduction on a blunt body by self-adaption of rear flexibly hinged flaps

We study the aerodynamics of a blunt-based body with rear flexibly-hinged rigid flaps, subject to a turbulent flow of Reynolds number Re=12000, under aligned and cross flow conditions with yaw angle β=0° and β=4°. To that aim, different values of the equivalent torsional stiffness are considered, to cover the range of reduced velocity U∗=(0,3.48] in water tank experiments. The effect of the angular deflection of plates on the drag and near wake flow is analyzed, experimentally and numerically. The results show that, in the range of U∗ herein considered, the plates undergo an inwards quasi-static, self-adaptive deflection, which is symmetric for yaw angles β=0° and asymmetric for β=4°. In particular, the plates feature small mean deformation angles for values of U∗<1, whereas a sharp and monotonic increase of such deflection occurs for U∗>1, i.e. for lower values of the hinge’s stiffness, with an asymptotic trend towards the larger values of U∗. A critical value of reduced velocity of U∗≃0.96 is obtained as the instability threshold above which plates depart from their initial equilibrium position. The progressive streamlining of the trailing edge translates into significant reductions of the associated mean drag coefficients. Thus, reductions close to 19% with respect to reference static plates configurations are obtained for the most flexible case of U∗=3.48 for both β=0° and β=4°. A close inspection of the near wake reveals that the inwards progressive mean displacement of the plates yields a reduction in the recirculation bubble size. A symmetric evolution of the recirculating bubble is observed for β=0°, whereas the bubble becomes asymmetric for β=4°, with a larger leeward clockwise vortex. In both cases, the drag coefficient is shown to vary linearly with the global aspect ratio of the recirculating bubble. The analysis of the numerical results shows that the reduced extension of the recirculating bubble significantly alters the formation length and intensity of the eddies size and associated pressure. It is observed that despite the local pressure decrease in the vortices shed from the trailing edges, the plates self adaption reduces their size and prevents the eddies from entering the cavity, thus, creating a dead flow region with a consequent pressure increase at the body base.

Influence of Viscous Damping Models on the Inelastic Response of Reinforced Concrete Columns and Bridges

The appropriate estimation of displacements is crucial in performance-based design. Among the options to assess deformation demands, Nonlinear Time History Analysis (NLTHA) is the most sophisticated. However, previous research has shown that NLTHA is sensitive to the viscous damping model definition, and there is substantial disagreement in the engineering community regarding damping model choices. Thus, the goal of this paper is to show the impact of viscous damping model assumptions on the nonlinear response of bridges. A displacement sensitivity study was conducted on several multi-span bridges using various viscous damping models and earthquake records. The results indicate that the mean displacement varies as a function of the displacement ductility level and damping model. In order of ascending displacement demand, the Wilson-Penzien model had the lowest demands followed by the Rayleigh-Initial stiffness, Mass proportional, Rayleigh-Tangent stiffness, Tangent stiffness proportional damping, and Zero-damping. Also, this paper proposes a new viscous damping model. We expect these findings to help practitioners understand the implications of the choice of the damping model and guide the analyst when selecting damping parameters.

Rate of moment convergence in the central limit theorem for the elephant random walk

The one-dimensional elephant random walk is a typical model of discrete-time random walk with step-reinforcement, and is introduced by Schütz and Trimper (2004 Phys. Rev. E 70 045101). It has a parameter : the case α = 0 corresponds to the simple symmetric random walk, and when α > 0 (resp. α < 0), the mean displacement of the walker at time n grows (resp. vanishes) like n α . The walk admits a phase transition at from the diffusive behavior to the superdiffusive behavior. In this paper, we study the rate of the moment convergence in the central limit theorem for the position of the walker when . We find a crossover phenomenon in the rate of convergence of the 2mth moments with inside the diffusive regime .

Rapid assessment of slope deformation in 3D point cloud considering feature-based simplification and deformed area extraction

Calculating deformation values and determining deformation areas are essential for slope monitoring and safety management. Recently, terrestrial laser scanning has been widely used for deformation monitoring due to to its speed and efficiency. However, handling a large amount of point cloud data to obtain the deformed area is still challenging. To rapidly evaluate slope deformation information, this study proposes a simplification algorithm for point cloud data based on multi-parameter feature preservation. The proposed method retains feature points (i.e. inflection points and edge points) and simplifies data with the octree structure. In addition, a method based on cloud-to-mesh for displacement is used where the winding number is introduced for the signed function. Next, the deformed area over the level of detection is extracted using density-based spatial clustering for applications with a noise clustering algorithm. To verify the reduction method, two types of slope field data are used for experiments. The results reveal that the proposed point cloud approach is superior to the conventional algorithms. Furthermore, the highway slope in Mianyang is selected as a case study to validate the performance of the proposed method. The entire monitoring area is stable with a deformation of approximately 0.43 mm, and only four regions are deformed over the study period. When the mean displacement value is considered in different deformation regions, the minimum deformation is −82.02 mm and the maximum deformation is 85.31 mm. Moreover, comparative experiments on deformation calculation are conducted and reveal the superior performance of the proposed method.

Comparing Emergency Department Stress of Lateral Compression Type 1 Pelvis Fractures With a Validated Instability Scoring System.

Lateral compression type 1 (LC1) pelvic ring injuries represent a heterogeneous group of fractures with controversial surgical indications. Recently, multiple institutions have suggested the safety and reliability of an emergency department (ED) stress to evaluate for occult instability. The purpose of this study was to correlate ED stress examination of LC1 pelvis fractures against a validated fracture instability scoring system. This was a retrospective review of a consecutive series of 70 patients presenting with minimally displaced LC1 fractures at a level 1 academic trauma center. All patients were stressed in the ED radiology suite, and displacement was measured by comparing calibrated stress radiographs with static radiographs (>10 mm displacement defined positivity). ED stress results were compared with radiographic scores assigned according to the validated Beckmann scoring system (score <7: stable-nonsurgical recommendation; score 7 to 9: indeterminant recommendation; and score >9: unstable-surgical recommendation). Thirteen patients had a positive ED stress examination, and 57 patients stressed negative. The mean displacement was significantly different between the three groups (Beckmann 5 to 6: 3.31 mm, SD = 2.4; Beckmann 7 to 9: 4.23 mm, SD = 3.2; Beckmann 10+: 12.1 mm, SD = 8.6; P < 0.001). Zero of 18 patients in the stable group stressed positive, and only 3 of 38 patients in the indeterminant group stressed positive (7.9%). Finally, 10 of 14 patients in the unstable group stressed positive (71.4%; P < 0.001) . Sacral displacement ( P = 0.001), superior ramus location ( P < 0.02), and sacral columns ( P < 0.001) significantly predicted ED stress positivity in multivariate analysis. Comparison of a validated instability scoring system with ED stress examination of minimally displaced LC1 fractures in awake and hemodynamically stable patients showed excellent correlation. This suggests that the ED stress examination is a useful diagnostic adjunct. LC1 fracture characteristics should be analyzed to determine which pelvic fracture characteristics determine occult instability before stress examination. Level III diagnostic.

Relationship of ulna styloid fracture to the distal radio-ulnar joint stability. A clinical, functional, and radiographic outcome study.

Ulna styloid fracture occurs approximately about 55% of all distal end of radius fractures. However, the clinical and functional outcome of these fractures remains indefinite. Only 56 patients with distal radius fractures had concomitant ulna styloid fractures. The mean age was 32 years (range: 18-69; SD: ± 12.7). The majority were men. The mean time from injury was 18.7 months (range: 6-84; SD: ± 13.3). The most common was Frykman 2, followed by 6, type 8, and type 4. All were closed fractures; 60.7% were base, and 39.3% were tip fractures. 50% were treated with casting, 48.3% plating, and 1.8% external fixation. The mean period of casting was 7.67 weeks (range: 4-16; SD ± 3.1). The ulna styloid was united in 35.7%. There is no significant difference in the range of movement between those with ulna styloid union and non-union. The Ballottement test and Piano key sign was statistically insignificant between both groups. All the displacements were dorsal except in 1 case. The mean displacement of ulna styloid is 1.88mm (SD±1.08, Range: 0.20-4.60mm). The mean VAS score at rest and work is not statistically significant. The mean grip strength and functional score (DASH) are similar in both groups. Ulna styloid fractures do not contribute to the DRUJ instability and the status of the union of the ulna styloid and the site of the ulna styloid fracture (tip or base) did not have a bearing on the range of movement and functional status of the affected wrist. Temporary DRUJ immobilization might allow TFCC recovery.

Ex Vivo Uniaxial Tensile Properties of Rat Uterosacral Ligaments.

This manuscript presents new experimental methods for testing the ex vivo tensile properties of the uterosacral ligaments (USLs) in rats. The USL specimens ([Formula: see text]) were carefully dissected to preserve their anatomical attachments, and they were loaded along their main in vivo loading direction (MD) using a custom-built uniaxial tensile testing device. During loading, strain maps in both the MD and the perpendicular direction (PD) were collected using the digital image correlation technique. The mean (± S.E.M.) maximum load and displacement at the maximum load were [Formula: see text] N and [Formula: see text] mm, respectively. The USLs were found to be highly heterogeneous structures, with some specimens experiencing strains in the MD that were lower than [Formula: see text] and others reaching strains that were up to [Formula: see text] in the intermediate region. At 0.5 kPa stress, a value reached by all the specimens, the mean strain in the MD was [Formula: see text] while at 5 kPa stress, a value achieved only by 9 out of the 21 specimens, the mean strain increased to [Formula: see text]. Under uniaxial loading, the specimens also elongated in the PD, with strains that were one order of magnitude lower than the strains in the MD; at the 0.5 kPa stress, the mean strain in the PD was recorded to be [Formula: see text] and, at the 5 kPa stress, the strain in the PD was [Formula: see text]. The directions of maximum principal strains remained almost unchanged with the increase in stress, indicating that little microstructural re-organization occurred due to uniaxial loading. This study serves as a springboard for future investigations on the supportive function of the USLs in the rat model by offering guidelines on testing methods that capture their complex mechanical behavior.

Safety and Efficacy of a Novel Approach to Pulmonary Vein Isolation Using Prolonged Apneic Oxygenation

BackgroundImproved ablation catheter–tissue contact results in more effective ablation lesions. Respiratory motion causes catheter instability, which impacts durable pulmonary vein isolation (PVI). ObjectivesThis study sought to evaluate the safety and efficacy of a novel ablation strategy involving prolonged periods of apneic oxygenation during PVI. MethodsWe conducted a multicenter, prospective controlled study of 128 patients (mean age 63 ± 11 years; 37% women) with paroxysmal atrial fibrillation undergoing PVI. Patients underwent PVI under general anesthesia using serial 4-minute runs of apneic oxygenation (apnea group; n = 64) or using standard ventilation settings (control group; n = 64). Procedural data, arterial blood gas samples, catheter position coordinates, and ablation lesion characteristics were collected. ResultsBaseline characteristics between the 2 groups were similar. Catheter stability was significantly improved in the apnea group, as reflected by a decreased mean catheter displacement (1.55 ± 0.97 mm vs 2.25 ± 1.13 mm; P < 0.001) and contact force SD (4.9 ± 1.1 g vs 5.2 ± 1.5 g; P = 0.046). The percentage of lesions with a mean catheter displacement >2 mm was significantly lower in the apnea group (22% vs 44%; P < 0.001). Compared with the control group, the total ablation time to achieve PVI was reduced in the apnea group (18.8 ± 6.9 minutes vs 23.4 ± 7.8 minutes; P = 0.001). There were similar rates of first-pass PVI, acute PV reconnections and dormant PV reconnections between the two groups. ConclusionsA novel strategy of performing complete PVI during apneic oxygenation results in improved catheter stability and decreased ablation times without adverse events. (Radiofrequency Ablation of Atrial Fibrillation Under Apnea; NCT04170894)

Evaluating future climate change exposure of marine habitat in the South East Pacific based on metabolic constraints

IntroductionOn-going climate change is now recognized to yield physiological stresses on marine species, with potentially detrimental effects on ecosystems. Here, we evaluate the prospect of using climate velocities (CV) of the metabolic index (Φ) for assessing changes in habitat in the South East Pacific.MethodsOur approach is based on a species with mean ecophysiotype (i.e. model species) and the use of a global Earth System Model simulation (CESM-LE) under RCP 8.5 scenario. The SEP is chosen as a case study as it hosts an Oxygen Minimum Zone and seamounts systems sustaining local communities through artisanal fisheries.Results and DiscussionOur results indicate that CVΦ pattern is mainly constrained by the oxygen distribution and that its sign is affected by contrasting oxygen trends (including a re-oxygenation in the upper OMZ) and warming. We further show that CVΦ is weakly dependent on physiological traits composing Φ, which conveys to this metrics some value for inferring the projected mean displacement and potential changes in viability of metabolic habitat in a region where physiological data are scarce. Based on sensitivity experiments to physiological traits and natural variability, we propose a general method for inferring broad areas of climate change exposure regardless of species-specific Φ. We show in particular that for the model used here, the upper OMZ region can be considered a “safe” area for the species with ecophysiotype close to that of 71 species used to derive the model species. Limitations of the approach and perspectives of this work are also discussed.

The Use of the Static Posturography to Assess Balance Performance in a Parkinson's Disease Population.

The literature has shown contradictory results so far about the use of posturography, especially static posturography, to evaluate balance performance in Parkinson’s disease (PD) populations. This study aimed to investigate the use of static posturography as a valid method to evaluate balance in a PD population. Fifty-two participants diagnosed with PD (Hoehn & Yahr stage: 1−3) were included in this cross-sectional study. All participants completed the following assessments: Hoehn and Yahr scale, Movement Disorder Society-Unified Parkinson’s Disease Rating Scale, Tinetti Scale, Berg Balance Scale, Activities-specific Balance Confidence scale, Timed Up and Go test, and Functional Reach Test. Sway parameters were analyzed with a baropodometric platform, under eyes open (EO) and eyes closed (EC) conditions, in a bipodal stance. Small to large correlations were observed between clinical balance tests and static posturography parameters, although the majority of these parameters correlated moderately. Considering posturographic variables, the highest correlation values were detected for total excursion (TE), mean velocity (MV), mean (X-mean), and root-mean-square (X-RMS) displacements in the medio-lateral directions. It was observed that posturographic parameters worsened as the disease progresses, although differences were only significant between the stages 1 and 3 in the H&Y scale (p < 0.05). Regarding the test condition, the visual deprivation worsened significantly all the static posturography parameters (p < 0.05), except the antero-posterior mean displacement (Y-Mean). Comparing visual conditions, the EC presented slightly higher correlation values with the clinical balance tests. Static posturography could be used as an objective complementary tool to clinical balance tests in order to assess and control balance performance, mainly to detect postural instability problems.

Corrective Osteotomy for Symptomatic Radial Head and Neck Malunions in the Skeletally Immature.

Radial head and neck fracture malunion can lead to pain, stiffness, deformity, and functional limitations. This study analyzed the early radiographic and functional outcomes of corrective osteotomy for symptomatic radial head and/or neck malunion in skeletally immature patients. Thirteen pediatric patients treated with corrective osteotomy for symptomatic radial head and/or neck malunion from 2004 to 2018 were identified. Radiographic union, range of motion, pain, and complications were recorded. Functional outcomes were assessed using the Broberg and Morrey Elbow Scale. The average age at the time of surgery was 12.3 years (range: 8.6 to 16.3). The mean time from injury to osteotomy was 7.5 months (range: 2 to 24.1mo). Before osteotomy, mean radial head-shaft angulation was 23 degrees (range: 5 to 57 degrees), mean displacement was 76% (range: 0 to 55), average elbow flexion contracture was 18 degrees (range: 0 to 60 degrees), and average elbow flexion was 112 degrees (range: 95 to 135 degrees). After a mean follow-up of 14.3 months, 12 of 13 osteotomies (92%) healed; 1 patient had a painless nonunion. The number of patients reporting pain decreased from 9 to 2 ( P =0.012). Radiographic alignment and range of motion improved in all patients. Mean angulation and displacement improved to 8 degrees (range: 2 to 15 degrees, P =0.001) and 3% (range: 0 to 18 degrees, P =0.001), respectively. Mean elbow flexion contracture was reduced to 5 degrees (range: 0 to 30 degrees, P =0.008), and the average elbow flexion increased to 128 degrees (range: 100 to 135 degrees, P <0.001). Three patients underwent implant removal for complications, including heterotopic ossification and avascular necrosis. Physeal arrest did not lead to any adverse sequelae. The sole case of avascular necrosis had a reduced range of motion but no pain. The mean postoperative Broberg and Morrey score was 91.1; 7 patients had excellent postoperative scores, 4 good, and 2 fair. Corrective osteotomy for symptomatic malunion of the radial head and/or neck in skeletally immature patients can improve elbow alignment, motion, pain, and function. Preservation of the soft-tissue attachments to the proximal epiphysis and rigid internal fixation are critical components of this surgical technique. Therapeutic Level IV.

Use of a commercial indoor positioning system for monitoring resting time and moving distance in group-housed dairy calves.

To assess the usefulness of a commercially available indoor positioning system for monitoring the resting time and moving distance in group-housed dairy calves as indicators of their health status, five dairy calves were housed in a free barn, and their coordinate was recorded. The mean displacement (cm/s) within a minute showed a double-mixture distribution. Actual observations revealed that the minutes in the first distribution with shorter displacement were mostly the time that the calves spent lying. To predict the daily lying time and moving distance, a mixed distribution was divided at a threshold value. The mean sensitivity (the proportion of total minutes predicted correctly as lying, in total minutes observed lying) was more than 92%. The daily fluctuation in lying time correlated well with the actual lying time (r = 0.758, p < 0.01). The range of fluctuations was 740-1308 min/day and 724-1269 m/day for daily lying time and moving distance, respectively. The rectal temperature was correlated with daily lying time (r = 0.441, p < 0.001) and distance moved (r = 0.483, p < 0.001). The indoor positioning system can be a useful tool for early illness detection in calves before the onset of symptoms in group-housing systems.

Intravital Imaging of Intestinal Intraepithelial Lymphocytes.

Intestinal intraepithelial lymphocytes (IEL) are a numerous population of T cells located within the epithelium of the small and large intestines, being more numerous in the small intestine (SI). They surveil this tissue by interacting with epithelial cells. Intravital microscopy is an important tool for visualizing the patrolling activity of IEL in the SI of live mice. Most IEL express CD8α; therefore, here we describe an established protocol ofintravital imaging that tracks lymphocytes labeled with a CD8α-specific monoclonal antibody in the SI epithelium of live mice. We also describe data acquisition and quantification of the movement metrics, including mean speed, track length, displacement length, and paths for each CD8α+ IEL using the available software. The intravital imaging technique for measuring IEL movement will provide a better understanding of the role of IEL in homeostasis and protection from injury or infection in vivo.

Consistências dos índices de capacidade baseados na distribuição normal de probabilidade

Abstract: Capability analysis seeks to estimate the probability that a process will produce compliant products. The capability indices are dimensionless parameters that measure how well the process can meet specifications. In the literature, eight capability indices are listed, among others, considering a stable process under statistical control and based on the normal probability distribution, defined by: Cp, Pp, Cpk, Ppk, Cpm, Ppm, Cpmk, and Ppmk. Basically, the index formulas differ in the calculations of the variability within and total, and of the shifts of the mean in relation to the nominal value and the nearest specification limit. The objective of this article was to compare these capacity indexes, and for that, it was chosen the most consistent estimator, that is, the one that improved the accuracy and efficiency as the number of observations increased. Thus, a simulation of 30,000 values of a normal random variable with a mean equal to zero and a standard deviation equal to one was performed. This made it possible to sample this process 1,000 times using 5, 10, 15, 20, 25, and 30 rational subgroups with individual observations or sample elements. Subsequently, 20 mean shifts were provoked, with values ranging from 0.1 to 2 and varying by 0.1 unit. According to the results, it was concluded that the indexes Cpk and Ppk were the most consistent in presenting higher accuracy and efficiency for at least 15 rational subgroups or sample elements, regardless of the magnitude of the mean displacement in relation to the nominal value.

Investigating Transformer Encoding Techniques to Improve Data-Driven Volume-to-Surface Liver Registration for Image-Guided Navigation.

Due to limited direct organ visualization, minimally invasive interventions rely extensively on medical imaging and image guidance to ensure accurate surgical instrument navigation and target tissue manipulation. In the context of laparoscopic liver interventions, intra-operative video imaging only provides a limited field-of-view of the liver surface, with no information of any internal liver lesions identified during diagnosis using pre-procedural imaging. Hence, to enhance intra-procedural visualization and navigation, the registration of pre-procedural, diagnostic images and anatomical models featuring target tissues to be accessed or manipulated during surgery entails a sufficient accurate registration of the pre-procedural data into the intra-operative setting. Prior work has demonstrated the feasibility of neural network-based solutions for nonrigid volume-to-surface liver registration. However, view occlusion, lack of meaningful feature landmarks, and liver deformation between the pre- and intra-operative settings all contribute to the difficulty of this registration task. In this work, we leverage some of the state-of-the-art deep learning frameworks to implement and test various network architecture modifications toward improving the accuracy and robustness of volume-to-surface liver registration. Specifically, we focus on the adaptation of a transformer-based segmentation network for the task of better predicting the optimal displacement field for nonrigid registration. Our results suggest that one particular transformer-based network architecture-UTNet-led to significant improvements over baseline performance, yielding a mean displacement error on the order of 4 mm across a variety of datasets.

Intraoperative arthrography favorably impacts the early outcome of operatively managed fractures of the lateral humeral condyle displaced 1–5 mm in children

BackgroundControversy exists surrounding the optimal approach to managing pediatric lateral humeral condyle fractures (LHCF). The difficulty in assessing the articular surface using radiography and the intra-articular element potentially involved make LHCF susceptible to complications and delayed diagnoses. Arthrography has been used to delineate the articular surface to aid in deciding whether closed or open reduction is necessary. However, there has been scarce evidence to determine the accuracy of using radiography versus arthrography to predict articular disruption in LHCF displaced 1–5 mm. This study assesses; (1) the utility of intraoperative arthrography in modifying the method of operative reduction, (2) the accuracy of plain radiography in identifying articular integrity, and (3) the clinical outcomes of early operative treatment.MethodsThis was a single-center prospective study that involved operatively treated pediatric LHCF with a displacement of 1–5 mm. Patient demographics, radiographic displacement, predicted radiographic articular integrity, articular integrity on arthrograms, modification of management and follow-up clinical outcomes were obtained.ResultsA total of 72 patients were included with a mean displacement of 2.6 mm and a mean follow-up of 16 months. The articular surface was disrupted in 21% of patients. The reduction method (open versus closed) was modified in 15 patients (21%) after an intraoperative arthrogram. Out of 25 patients with displacement < 2 mm, four of which (15%) had disrupted articular surface and were subsequently treated with open reduction internal fixation (ORIF). While eleven patients with > 4 mm displacement had an intact articular hinge that were managed with closed reduction and percutaneous pinning (CRPP). All patients achieved union with no documented major complications. The ability of radiography to discriminate between disrupted/ intact articular integrity decreases as displacement decreases.ConclusionsData from this study suggest using the degree of displacement measured on plain radiography is insufficient in predicting articular integrity for fractures displaced 1–5 mm. The use of arthrography guides reduction method and adequacy, avoiding scenarios of unnecessary open reduction and insufficient closed reduction. Further, a significant amount of outliers exist that have intact articular hinges above 4 mm and disrupted hinges below 2 mm of displacement. Finally we report favorable outcomes using a lower threshold for early operative treatment.

Improved estimation of time-varying mean displacement and parametric study of biaxial effect on inelastic responses of high-rise buildings to wind

Three reduced-order building models with different biaxial hysteretic generalized restoring force and displacement relations were developed using static modal pushover analysis of a nonlinear finite element model of a 60-story steel building. It was illustrated that the reduced-order models can give accurate estimations of fluctuating responses but overestimate the time-varying mean alongwind displacement. The nonphysical displacement drift of the Bouc-Wen hysteresis model is responsible for this overestimation. An improved estimation of time-varying mean alongwind displacement was presented. A comprehensive parametric study concerning the influence of biaxial interaction on inelastic responses was also performed. The biaxial interaction leads to faster growth of time-varying mean displacement but does not affect its steady-state value. It results in increase in the low-frequency component but decrease in the resonant component of alongwind displacement. It leads to more reduction in alongwind acceleration. The crosswind response, which is greater than the alongwind response, is not affected, or only slightly reduced when both alongwind and crosswind responses are close to each other in magnitude. The peak ductility demand of a combined alongwind and crosswind response is less affected by the biaxial interaction. The new insights of this study can have wide applications to other buildings and wind directions.