Rotation Of Segment Research Articles

History and Future Development of Morphing-Wing Aircrafts

Morphing-wing aircraft can alter the shape of their wings to achieve different flight performances. Such changes are made to achieve the optimum aerodynamic profile for the current flight environment. The morphing wings greatly improve the flight efficiency and reduces the energy loss in different environments. Morphing designs can be categorized into three distinct types based on their fundamental mechanisms: rotation of specific segments or the entire wing, telescoping, and inflation of particular components or the entire wing. With the continuous technological innovation and practical applications, many famous type of morphing-wing aircrafts have left marks in humans aviation history. Although morphing-wing aircrafts have been shown to be mostly withdrawn from service, the research on morphing-wing aircraft has promoted the development of aviation technology and provided valuable reference for the design of modern fighter aircraft. In order to speculate on the future development of morphing-wing aircraft design, this article overviews the history of morphing-wing aircraft, analyses the reasons for the abandonment of morphing-wing design, and finally discusses the potential trend of morphing-wing aircraft. This article may offer a reference for the design of aircraft.

Evaluation of the effects of asymmetric lumbosacral transitional vertebra on pelvic morphology in dogs using ventrodorsal radiographs

BackgroundA lumbosacral transitional vertebra (LTV) is a congenital anomaly of the caudal vertebral column. It has been associated with asymmetrical canine hip dysplasia (CHD) and cauda equina syndrome (CES) in German Shepherd dogs. This retrospective cross-sectional study aims to report the potential influence of asymmetric LTV on pelvic anatomy using ventrodorsal (VD) radiographs.ResultsThe results are based on the evaluation of VD radiographs of 13,950 dogs from 14 breeds; an LTV was identified in 18.5%. The LTV segments were allotted into symmetrical (78.6%) and asymmetrical (21.4%) categories. An asymmetrical CHD grade was observed in 12.4% of the dogs, of which 39.7% had asymmetrical LTV. An asymmetric LTV was associated with an uneven sacroiliac joint length, in which the shortest sacroiliac joint is positioned more caudally, resulting in a reduced distance to the hip joint (P < 0.001). Rotation of the asymmetrical LTV segment about the long axis was associated with opposite pelvis rotation vertically (P < 0.001). Also, long-axis rotation of the asymmetric LTV segment was associated with an elevation of the pelvis (P < 0.001), promoting an asymmetrical CHD grade (P < 0.001).ConclusionsThis study suggests a compensatory mechanism for the sacroiliac joint related to an asymmetrical LTV. Counter-rotation between the pelvis and the LTV segment vertically may straighten the lower back. The asymmetrical LTV segment most likely affects the rotation of the pelvis and may indirectly promote an asymmetrical CHD grade.

Comparative Evaluation of L Plate Versus Z Plate for One Point Fixation in Zygomatic Fractures

The zygomatic bone’s lateral prominence and convexity make it the most important bone to provide aesthetic facial appearance and set the face width, but at the same time, this prominence and convexity make this bone more susceptible to injury. Among facial injuries, zygomatic-complex fractures or tripod fractures are the second most common fractures after nasal fractures. This study has performed a comparative assessment of fixation of zygomatic buttress by L and Z shaped plate. Fourteen zygomatic-complex fracture patients were selected and split into two groups, further divided into two subgroups (A, B). Group A patients were treated with a titanium Z shaped plate and Group B with L shape plate. One point fixation was performed and was observed in terms of stability, aesthetics and prevention of vertical or horizontal axis of rotation of the fracture segment. Z-shaped plates showed some advantage over L-shaped plates so there use can be preferred in complex fractures where comminuted bone pieces are scattered.

Is It Enough to Stop Distal Fusion at L3 in Mild to Moderate Lenke 5C Adolescent Idiopathic Scoliosis Patients?

There has been no definitive conclusion on the selection of the lowest instrumented vertebra (LIV) in Lenke 5C adolescent idiopathic scoliosis (AIS) patients. The purpose of this study was to evaluate whether it is enough to stop distal fusion at L3 in mild to moderate Lenke 5C AIS patients with posterior selective lumbar fusion, Ponte osteotomies and segmental direct vertebra rotation and to analyze the risk factors for postoperative complications in patients selecting L3 as the LIV. A retrospective review was conducted on 106 Lenke 5C AIS patients who underwent corrective surgery in our institution from 2010 to 2021, with a minimum 2-year follow-up. The LIV was L3 or L4. According to the LIV, patients were initially divided into Group I (the LIV was L3) and Group II (the LIV was L4). Then, Group I was further divided into a complication group and a non-complication group. Demographics, radiological parameters, postoperative complications, and clinical outcomes were recorded. Univariate analysis and multivariate logistic analysis were used to identify the risk factors for postoperative complications in patients with L3 as the LIV. There were no significant differences in the demographics, radiological parameters, postoperative complications, or clinical outcomes between Group I and Group II (p > 0.05), and the outcomes were satisfactory in both groups. The main postoperative complications were distal adding-on (11 cases), coronal imbalance (16 cases), proximal junctional kyphosis (2 cases), and internal fixation failure (4 cases). Logistic regression analysis revealed that age and postoperative C7-CSVL were independent predictors of postoperative complications when selecting L3 as the LIV. Terminating the distal fusion level at L3 was practical for mild to moderate Lenke 5C AIS patients. For patients selecting L3 as the LIV, younger patients should be cautious, and maintaining postoperative coronal balance is necessary for avoiding postoperative complications.

Changes in the Centers of Rotation in Different Prosthetic Segments Following Continuous Two-Level Cervical Disc Replacement: A Retrospective Study

To observe the short-term to medium-term therapeutic effects and radiological outcomes of adjacent 2-level cervical spondylosis treated with artificial cervical disc replacement (ACDR) using Mobi-C and Bryan discs. To observe changes and discrepancies in the flexion-extension centers of rotation (FE-COR) of different ACDR segments. Twenty-four patients undergoing 2-level (C4/5 and C5/6) ACDR were analyzed retrospectively (11 patients in the Mobi-C group and 13 patients in the Bryan group). Clinical outcomes were assessed using modified Japanese Orthopedic Association score, Neck Disability Index, and visual analog scale. Preoperative and 2years' follow-up radiographs were collected to compare total cervical spine curvature (C2-C7) range of motion (ROM), upper and lower ACDR segmental ROM, and the operated adjacent segmental ROM. The FE-COR of the ACDR segment was measured using the mid-plumb line method. The degree of disc degeneration in the adjacent segment was observed. At the 2years' follow-up, in both group, the modified Japanese Orthopedic Association score increased significantly, and the Neck Disability Index and neck and upper extremity visual analog scale scores decreased significantly compared with preoperative (P<0.05). There were no significant statistical differences in postoperative scores between the 2 groups (P > 0.05). The overall cervical ROM, the upper and lower segmental ROM at the 2years' follow-up showed no significant statistical differences compared with the preoperative period (P > 0.05). There was no statistically significant difference in the adjacent segmental ROMs compared with the preoperative period (P > 0.05). Furthermore, the statistical analysis revealed no significant differences in the measurements of the ROM at each time points between the Mobi-C Group and the Bryan Group (P > 0.05). There was no significant difference in the preoperative FE-COR-X (indicating the horizontal position of the point in the coordinate system) and FE-COR-Y (indicating the vertical position of the point in the coordinate system) of upper or lower ACDR segments between the 2 groups (P > 0.05). At the 2years' follow-up, there were significant differences both in FE-COR-X and FE-COR-Y between the 2 groups (P < 0.05). For the Mobi-C group, in both the upper and lower segment, the FE-COR-X significantly increased compared with preoperative (P < 0.05), while the FE-COR-Y decreased compared with preoperative (P < 0.05). For the Bryan group, no significant changes were observed in the upper or lower segment in both FE-COR-X and FE-COR-Y compared with preoperative (P > 0.05). Fourty-eight adjacent segments (24 superior and 24 inferior segments) were included in the studies of adjacent segment disease. Four segments showed imaging adjacent segment disease (4/48, 8.33%) in 4 patients, of which 2 were mild and 2 were moderate according to the grading criteria. Among them, 2 were from the Mobi-C group and 2 were from the Bryan group. No severe imaging degeneration was observed. In continuous 2-level cervical ACDR surgery, both Mobi-C and Bryan artificial cervical discs achieved satisfactory clinical outcomes in the short to medium term postoperatively. The FE-COR exhibited different trends of change. In the Mobi-C group, the FE-COR for both upper and lower segments shifted anteriorly and inferiorly, whereas in the Bryan group, whether upper or lower, the FE-COR remained closer to the preoperative state. The changes in FE-COR did not significantly affect the short-term to medium-term clinical outcomes postoperatively.

A Comparative Study on the Consistency of Ultrasound and X-Ray in Assessing Risser Sign.

Adolescent idiopathic scoliosis (AIS) is a 3-dimensional spinal deformity involving lateral curvature, sagittal plane imbalance, and vertebral rotation. In China, AIS affects over 3 million individuals, with 300,000 new cases annually. AIS impacts physical and psychological well-being, necessitating tailored treatment plans based on growth risk factors. This study evaluates the consistency of ultrasound and X-ray assessments of the Risser sign in AIS patients and explores correlations between iliac crest distance and pelvic rotation degree. This prospective study enrolled 80 patients diagnosed with AIS from June to September 2023 at Changzhou Sports Hospital. Eligible participants were aged 10-18 with a Cobb angle >10°. Ultrasonographic examinations were conducted by 3 experienced physicians using the VINNO V10 portable ultrasound system. The primary outcome was the Risser stage determined by X-ray and ultrasound, with secondary outcomes including thoracic and thoracic-lumbar segment rotation angles. Statistical analyses included kappa statistics, correlation analyses, and multiple regression. Among the 77 valid cases, 154 iliac wings were evaluated, with a high concordance rate of 77% between ultrasound and X-ray assessments. kappa values for left and right iliac crests were 0.723 and 0.808, respectively. Grouping Risser grades (0-1, 2-3, and 4-5) into 3 categories yielded kappa values of 0.93, 0.96, and 0.93, indicating high consistency. Significant correlations were found between iliac crest distances and rotation angles (left iliac crest distance and left thoracic rotation angle, r = 0.56, P < .001; right iliac crest distance and right thoracic-lumbar rotation angle, r = 0.69, P < .001; right iliac crest distance and right thoracic rotation angle, r = 0.39, P < .01). Ultrasound is a reliable, radiation-free alternative to X-ray for assessing the Risser sign in AIS patients. Despite observed inconsistencies in intermediate Risser grades, ultrasound's ability to reduce radiation exposure and provide consistent results makes it a valuable tool in clinical practice. Further research is needed to optimize ultrasound techniques and explore its potential for early detection and intervention in scoliosis management.

CONGENITAL ABSENCE OF PULMONARY ARTERY

Isolated unilateral absence of a proximal pulmonary main artery is a rare congenital condition with a prevalence of 1 in 200,000 (1). The first case was reported in 1868, and to date, 350 cases have been reported (2). It usually occurs in conjunction with other cardiovascular anomalies such as tetralogy of Fallot, VSD, truncus arteriosus, etc. (2), and is typically diagnosed in childhood. Survival into adulthood is rare. Symptoms of this condition can include shortness of breath, chest pain, hemoptysis, reduced exercise tolerance, pleural effusion, and recurrent infections. We encountered a case of a 22-year-old female presenting with these symptoms. Initially, the symptoms suggested pulmonary embolism. However, further investigation through CTPA and Echocardiography revealed the absence of the left pulmonary artery. This case report emphasizes that patients showing signs and symptoms indicative of PAH should also be evaluated for the absence of a pulmonary artery." The pulmonary arteries originate from the sixth aortic arch during the sixteenth week of normal embryonic development. The proximal segment of the 6th aortic arch forms the initial portion of the right &amp; left pulmonary arteries, respectively. The link on the arch's right side vanishes, whereas it establishes a connection through the ductus arteriosus on the left side. Pulmonary artery agenesis arises from the aberrant rotation of the afflicted segment's attachment to the aortic arch and dysfunctions during migration (3). Certain publications utilize the phrase “proximal blockage of the pulmonary artery” instead of “agenesis” to describe this anomaly. Although the intraparenchymal distal segment of the pulmonary artery is miniature, it is safeguarded (4). The prevalence of bronchopneumonia is ascribed to multiple causes, such as diminished lung tissue perfusion, impaired mucosal defense, and a possible unbalance of protease-antiprotease enzymes. Moreover, increased collateral blood flow may be associated with the onset of hemoptysis.

Adjustment of segmental rotations to achieve both racket speed and accuracy at various impact heights during a two-handed backhand stroke

ABSTRACT This study investigated the influence of impact height and competitive level on racket speed and stroke accuracy by analysing segmental angular kinematics under a random ball condition. High- (HQ, n = 7) and low-quality (LQ, n = 7) groups were determined by k-means clustering of the ratio of ball landing in the target (accuracy) and racket speed decrease. HQ showed higher accuracy (48.3% vs. 32.4%), less speed decrease at lower impact heights (−4.4% vs. −10.3%) and better competitive level ranking [median (1st–3rd quartiles); 4 (2–7)] than LQ [10 (8–13)]. HQ produced greater racket speed (24.4 vs. 21.6 m/s), especially with a notable horizontal velocity (23.8 vs. 20.8 m/s) of the racket at lower impact height, which was attributed to the central role of greater angular velocity of pelvis and thorax in the hitting direction. Both groups showed similar adjustment mechanisms that due to the decrease in angular velocity of pelvis, players increased the relative rotation angle between pelvis and thorax to maintain angular velocity of thorax when transitioning from low to high impact heights. Our findings suggest that players should emphasise the coordination between pelvic and thoracic rotations according to impact heights to maintain racket speed while controlling ball landing position.

Chirality Interplay between the Interior and Exterior of Metal–Organic Cages

AbstractA series of metal–organic cages featuring two stereogenic elements, in terms of the twisting of amide moieties within the ligand backbones and the rotation of diazaanthracene segments along the ligand ridges, were exploited. These two chiral components are correlative and serve as relays for transmitting chirality information between the internal and external cages. The chirality information induced by a chiral guest inside the cage cavity can pass through the cage framework and influence the orientation of the diazaanthracene segments on the periphery of the cage. In turn, the chirality of a stereogenic center within the diazaanthracene segments can transfer back into the cavity, enabling discrimination of enantiomeric guests.

Comparison of three different internal fixation methods in the treatment of femoral neck fracture

ObjectiveThis study aimed to assess the efficacy of three different fixation methods in treating femoral neck fractures in young patients. MethodsA retrospective analysis was conducted on 35 young patients with femoral neck fractures who underwent surgical treatment. Among them, 16, 12, and 7 patients underwent fixation with three cannulated compression screws (3CS), the femoral neck system (FNS), and the compound compression system (CCS), respectively. Data, including fracture classification, injury-to-surgery time, surgery duration, intraoperative blood loss, fluoroscopy instances, fracture healing time, complications, and Harris score at the final follow-up, were collected and analyzed to compare clinical outcomes among the three fixation methods. ResultsAll patients were followed for at least 6 months, exhibiting no significant differences in age, gender, injury side, fracture type, or injury-to-operation time among the three groups (P > 0.05). The FNS and CCS groups exhibited shorter operation durations and fewer intraoperative fluoroscopy instances compared to the 3CS group (P < 0.01). Despite the minimally invasive nature of 3CS, the FNS and CCS groups experienced higher intraoperative blood loss (P < 0.01). During follow-up, only one patient with 3CS fixation developed nonunion. Additionally, patients treated with 3CS demonstrated a higher incidence of femoral head necrosis and severe femoral neck shortening than the FNS and CCS groups. Excluding patients with combined nonunion, no significant difference in mean fracture healing time was observed among the three groups (P > 0.05). At the last follow-up, the FNS and CCS groups showed higher Harris scores (P < 0.05). ConclusionsBoth FNS and CCS are effective internal fixation systems for the treatment of femoral neck fractures in young patients, yielding more satisfactory clinical functional outcomes than 3CS. Comparatively, the CCS system presents a higher risk of iatrogenic rotation of the proximal fracture segment. Therefore, we advocate the insertion of two to three 2.5 mm Kirschner wires from the upper edge of the femoral neck along the axial direction before CCS lag screw insertion to resist iatrogenic rotational stress.

Finite Element Analysis of Cervical Spine Kinematic Response during Ejection Utilising a Hill-Type Dynamic Muscle Model.

To determine the impact of active muscle on the dynamic response of a pilot's neck during simulated emergency ejection, a detailed three-dimensional (3D) cervical spine (C0-T1) finite element (FE) model integrated with active muscles was constructed. Based on the Hill-type model characterising the muscle force activation mechanics, 13 major neck muscles were modelled. The active force generated by each muscle was simulated as functions of (i) active state (Na), (ii) velocity (Fv(v)), and (iii) length (FL(L)). An acceleration-time profile with an initial acceleration rate of 125 G·s-1 in the 0-80 ms period, reaching peak acceleration of 10 G, then kept constant for a further 70 ms, was applied. The rotational angles of each cervical segment under these ejection conditions were compared with those without muscles and with passive muscles derived from the previous study. Similar trends of segmental rotation were observed with S- and C-curvature of the cervical spine in the 150 ms span analysed. With active muscles, the flexion motion of the C0-C2 segments exhibited higher magnitudes of rotation compared to those without muscle and passive muscle models. The flexion motion increased rapidly and peaked at about 95-105 ms, then decreased rapidly to a lower magnitude. Lower C2-T1 segments exhibited less variation in flexion and extension motions. Overall, during emergency ejections, active muscle activities effectively reduce the variability in rotational angles across cervical segments, except C0-C2 segments in the 60-120 ms period. The role of the active state dynamics of the muscles was crucial to the magnitude of the muscle forces demonstrated. This indicates that it is crucial for pilots to consciously contract their muscles before ejection to prevent cervical spine injuries.

An observational study of quality of motion in the aging cervical spine: sequence of segmental contributions in dynamic fluoroscopy recordings

BackgroundThe term ‘physiological motion of the spine’ is commonly used although no proper definition exists. Previous work has revealed a consistent sequence of cervical segmental contributions in 80–90% of young healthy individuals. Age has been shown to be associated with a decreased quantity of motion. Therefore, it is of interest to study whether this sequence persists throughout aging.The aim of this prospective cohort study is to investigate if the consistent sequence of cervical segmental contributions in young asymptomatic individuals remains present in elderly asymptomatic individuals.MethodsIn this prospective cohort study, dynamic flexion to extension cinematographic recordings of the cervical spine were made in asymptomatic individuals aged 55–70 years old. Individuals without neck pain and without severe degenerative changes were included. Two recordings were made in each individual with a 2-to-4-week interval (T1 and T2). Segmental rotation of each individual segment between C4 and C7 was calculated to determine the sequence of segmental contributions. Secondary outcomes were segmental range of motion (sRoM) and sagittal alignment.ResultsTen individuals, with an average age of 61 years, were included. The predefined consistent sequence of segmental contributions was found in 10% of the individuals at T1 and 0% at T2. sRoM and total range of motion (tRoM) were low in all participants. There was no statistically significant correlation between sagittal alignment, degeneration and sRoM in the respective segments, nor between cervical lordosis and tRoM.ConclusionsThis study shows that aging is associated with loss of the consistent motion pattern that was observed in young asymptomatic individuals. The altered contribution of the cervical segments during extension did not appear to be correlated to the degree of degeneration or sagittal alignment.Trial registrationclinicaltrials.gov NCT04222777, registered 10.01.2020.

The effect of tongue reduction for preventing adverse effects in patients undergoing class III orthognathic surgery: a three-dimensional comparative analysis.

This study aims to evaluate the potential benefits of combining tongue reduction with mandibular setback surgery in patients undergoing class III orthognathic surgery. Specifically, we investigated whether this combined approach reduced the risk of surgical relapse, condylar resorption, and airway space reduction by mitigating tongue pressure on the mandible. The study retrospectively enrolled patients who had undergone bilateral sagittal split ramus osteotomy (BSSRO) with at least 5 mm of setback and met the criteria of a body mass index > 20 kg/m2 and tongue volume > 100 mm3. The study included 20 patients with 10 in the tongue reduction group (TR, n = 10) and 10 in the BSSRO only group (SO, n = 10). The volumetric changes of the total airway space were significantly different between the TR and SO groups (p = 0.028). However, no significant differences were observed in the condylar resorption and postoperative relapse between the groups (p = 0.927 and 0.913, respectively). The difference between the resorption of the anterior and posterior segments of the condyle was also statistically insignificant (p = 0.826). Postoperative counterclockwise rotation of the proximal segment only demonstrated a significant correlation with postoperative relapse (p = 0.048). The reduction in tongue volume demonstrated a preventive effect on the reduction of the airway space after mandibular setback, although it did not yield statistical significance concerning surgical relapse and condylar volume. The counterclockwise rotation of the proximal segment might be responsible for the forward displacement of the distal segment and postoperative relapse. However, the clinical implications of this finding should be interpreted with caution owing to the limited sample size CLINICAL RELEVANCE: Tongue reduction could potentially serve as a preventive measure in preserving the airway space and might be beneficial in mitigating the risk of obstructive sleep apnea in patients with class III deformity.

Predicting elbow load based on individual pelvis and trunk (inter)segmental rotations in fastball pitching

ABSTRACT The baseball pitch is a repetitive, full-body throwing motion that exposes the elbow to significant loads, leading to a high incidence of elbow injuries. Elbow injuries in pitching are often attributed to high external valgus torques as these are generally considered to be a good proxy for the load on the Ulnar Collateral Ligament. The aim of the study is to contribute to elbow load monitoring by developing a prediction model based on the pelvis and trunk peak angular velocities and their separation time. Eleven male youth elite baseball pitchers (age 17 ± 2.2 years) threw 25 fastballs at full effort off a mound. Two-level varying-intercept, varying-slope Bayesian models were used to predict external valgus torque based on (inter)segmental rotation in fastball pitching with pitcher’s weight and height added to strengthen the individualisation of the prediction. The results revealed the high predictive performance of the models including a set of kinematic parameters trunk peak angular velocity and the separation time between the pelvis and trunk peak angular velocities. Such an approach allows individualised prediction of the external valgus torque for each pitcher, which has a great practical advantage compared to group-based predictions in terms of injury assessment and injury prevention.

Towards Wearable and Portable Spine Motion Analysis Through Dynamic Optimization of Smartphone Videos and IMU Data.

Monitoring spine kinematics is crucial for applications like disease evaluation and ergonomics analysis. However, the small scale of vertebrae and the number of degrees of freedom present significant challenges for noninvasive and convenient spine kinematics estimation. This study developed a dynamic optimization framework for wearable spine motion tracking at the intervertebral joint level by integrating smartphone videos and Inertia Measurement Units (IMUs) with dynamic constraints from a thoracolumbar spine model. Validation involved motion data from 10 healthy males performing static standing, dynamic upright trunk rotations, and gait. This data included rotations of ten IMUs on vertebrae and virtual landmarks from three smartphone videos preprocessed by OpenCap, an application leveraging computer vision for pose estimation. The kinematic measures derived from the optimized solution were compared against simultaneously collected infrared optical marker-based measurements and in vivo literature data. Solutions only based on IMUs or videos were also compared for accuracy evaluation. The proposed optimization approach closely matched the reference data in the intervertebral or segmental rotation range, demonstrating minimal angular differences across all motions and the highest correlation in 3D rotations (maximal Pearson and intraclass correlation coefficients of 0.92 and 0.94, respectively). Time-series changes of joint angles also aligned well with the optical-marker reference. Dynamic optimization of the spine simulation that integrates IMUs and computer vision outperforms the single-modality method. This markerless 3D spine motion capture method holds potential for spinal health assessment in large cohorts in real-world settings without dedicated laboratories.

Experimental study on the mechanical properties of longitudinal joints of shield tunnels under large deformation conditions

Known to be the weakest part of the shield tunnel lining rings, the longitudinal joints render the lining rings prone to large deformation and related diverse defects under nonuniform pressure loading, thereby seriously compromising the safety, serviceability and durability of the tunnel structure. In light of the paucity of studies regarding the performance of joints under large deformation, this paper presents a series of experiments examining the damage mechanism of longitudinal joints under large deformation and investigating the effects of the bolt strength, initial joint configuration, and loading level on the mechanical properties of longitudinal joints. Moreover, a finite element model was developed for the joint, capable of simulating large deformation and bolt yielding. Results show that the specimen’s failure is characterized by concrete cracking and spalling at the compression side of the joint, and/or the thread stripping or fracture failure of the bolts. Besides, an increase in bolt strength can increase the bending capacity of the joint. The discontinuous joint configuration determines the compression height of the joint section cannot be continuously changed, which results in an abrupt change in structural stiffness and a four-stage change in bolt strain. Changes in the loading level not only affect the joint’s bending capacity to some extent, but also alter how cracks develop near the joint. Furthermore, the relationship between the joint opening angle and the segmental rotation angle proves the rigid body deformation characteristics of the segment before the bolts yielded. With the segmental rotation angle increased, the maximum joint opening width and mid-span deflection increased linearly, but the compression height decreased meantime. In addition, the relationship between the bolt strain and the segmental rotation angle exhibited a two-stage linearity after the bolt began to be stressed.

Flextegrity arched structures for Lunar bases built from indigenous materials

Flextegrity is a broad structural concept, represented here by a chain of perforated massive segments in dry contact, coupled by a passing-through pre-tensioned tie-rod (tendon). Contact surfaces realize pure rolling along tailor-designed pitch lines, so that the relative rotation of adjacent segments determines the tendon elongation: the bending constitutive law can be optimized simply by re-shaping the contact surfaces. Flextegrity arches are placed side by side to form a vault, pressurized via an interposed air-tight membrane. The arch follows an almost complete circle (the vault approaches a tube), to minimize the actions on the foundations from internal pressure. The structure also supports a thick radiation shield above, made up of loose Lunar debris. The main characteristic is that the massive segments can be made from cast Lunar regolith, fused into solar-powered devices, whose weight is mitigated by the reduced Lunar gravity. Huge savings on mission budget are expected, because the only components from Earth are the tendons, made of high-performance lightweight carbon nanotube fibers, and the air-tight membrane. Small-scale prototypes are manufactured from cast concrete. The structural response is analyzed through a theoretical model. The concept is applied to a Moon base example, verifying compatibility with the strength of Lunar regolith under various actions, including meteoroid impact.

Heritability of dental arches and occlusal characteristics: a systematic review and meta-analysis.

The genetic basis of dentoalveolar characteristics has been investigated by several studies, however, the findings are equivocal. The objective of this systematic review and meta-analysis was to evaluate the heritability of dental arches and occlusal parameters in different stages of human dentition. Electronic databases PubMed, Embase, Scopus, Web of Science, and Dentistry and Oral Science Source were searched up to August 2023 without the restriction of language or publication date. Empirical studies investigating the heritability of dentoalveolar parameters among twins and siblings were included in the review. Study selection, data extraction, and risk of bias assessment were performed independently and in duplicate by two authors and a third author resolved conflicts if needed. Joanna Briggs Institute's critical appraisal tool was used to evaluate the risk of bias among studies and the certainty of evidence was assessed using the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) criteria. Twenty-eight studies were included in the systematic review, of which 15 studies reporting heritability coefficients in the permanent dentition stages were deemed suitable for the meta-analysis. Random-effects meta-analyses showed high heritability estimates for maxillary intermolar width (0.52), maxillary intercanine width (0.54), mandibular intermolar width (0.55), mandibular intercanine width (0.55), maxillary arch length (0.76), mandibular arch length (0.57), and palatal depth (0.56). The heritability estimates for the occlusal parameters varied considerably, with relatively moderate values for crossbite (0.46) and overbite (0.44) and low values for buccal segment relationship (0.32), overjet (0.22), and rotation and displacement of teeth (0.16). However, the certainty of evidence for most of the outcomes was low according to the GRADE criteria. Based on the available evidence, it can be concluded that the dental arch dimensions have a high heritability while the occlusal parameters demonstrate a moderate to low heritability. PROSPERO (CRD42022358442).

Insights into Entropy Change of β2 Relaxation in Retraction of Uniaxially Stretched Polyimide Films

AbstractStretching has been extensively applied for decades in the production of polyimide (PI) materials with improved mechanical, electrical, and thermal properties. Meanwhile, a detailed understanding of the molecular motions during stretching is still limited. Herein, the thermomechanical behaviors of uniaxially stretched PI films prepared from 3,3′,4,4′‐biphenyl tetracarboxylic dianhydride (BPDA) and 2,2′‐bis (trifluoromethyl) benzidine (TFDB) are studied, and the possible molecular motions responsible for the sub‐glass transition temperature (Tg) stretchability and retraction after stretching are systematically investigated. Based on X‐ray diffraction and dynamic mechanical analysis, it is revealed that both the sub‐Tg stretchability and retraction correlates with β2 relaxation, which originates from the highly cooperative molecular motions of conformational rotations involving segmented BPDA units. A thermodynamic model is established and applied for the analysis of the retraction behaviors of stretched BPDA‐TFDB PI films. It is found that the increase of entropy under stretching plays a significant role in most retraction cases. However, as the stretching temperature increases, the α relaxation‐correlated large‐scale molecular motions emerge. Such motions partially counterbalance the conformational rotations of BPDA segments, leading to an enhanced contribution of enthalpy decrease during the retraction of BPDA‐TFDB PI films.

Morphological Changes of the Mandibular Angle After Orthognathic Surgery with Class III Deformity in East Asia.

The aims of this study were to analyze the morphological changes of the mandibular angle after orthognathic surgery for mandibular setback and investigate related factors. This retrospective study included patients from January 2017 to December 2021 diagnosed with skeletal class III deformity who underwent BSSRO (Group I) or bimaxillary surgery (Group II). Preoperative (T0), within 1month postoperatively (T1), and 6months postoperatively (T2) CT scans were collected from 61 patients to three-dimensionally analyze the proximal segment displacement, the linear and angular changes of the mandibular angle. The gonion points moved posteriorly and laterally (P < 0.001), while the inferior movement was not significant (P = 1.000, P = 0.274). The intergonial width increased by 3.32 ± 1.87mm and 2.34 ± 1.77mm as revealed by T2 CTs, respectively, in Group I and Group II. Mandibular angle decreased in both groups and by 1.41 ± 2.95° in Group I and 1.37 ± 3.41° in Group II. The increase in intergonial width between T1 and T0 was negatively correlated with the preoperative mandibular angle (P = 0.003) and positively correlated with the transverse outward movement of the proximal segment (P < 0.001). After surgery, the intergonial width increased and the inferior and posterior border of the proximal segment flared outward. The changes in intergonial width and mandibular angle were mainly related to the rotation of the proximal segment, which has a certain impact on the aesthetics of the lower face. Therefore, controlling the position of the proximal segment is of vital importance to lessen the changes in the mandibular angle area.Level of Evidence III. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .