Axis Of Head Research Articles

Dynamic changes of otolith organ function before and after repositioning in patients with benign paroxysmal positional vertigo detected by virtual reality auxiliary technology: A cohort study.

To dynamically investigate otolith function in patients with benign paroxysmal positional vertigo (BPPV) before, after, and 1 month after repositioning, and explore the possible compensation mechanisms. Thirty-six patients confirmed with BPPV (canal lithiasis) treated in our hospital between August 2020 and March 2021, as well as 36 health controls matched for age and gender (normal control group, NC group) were enrolled. For NC group, the virtual reality (VR) auxiliary static subjective visual vertical (SVV), subjective visual horizontal (SVH), and SVV of dynamic unilateral centrifugation (DUC), were measured at inclusion. For the BPPV group, visual analog scale (VAS) was used to assess the vertigo degree, while static SVV, SVH, and DUC were performed before, after, and 1 month after repositioning. First, we compare the deviations of SVV0/SVH0° when the subject's head is in the positive position, and SVV of DUC between BPPV and NC groups before repositioning, after which we compared the deviations in SVV45, SVV90, SVH45, SVH90°, and SVV of DUC between the affected and unaffected sides before repositioning. Finally, paired t-test was used to compare the VAS score, deviations in static SVV0, SVV45, SVV90, SVH0, SVH45, and SVH90°, and deviations in SVV of DUC before, after, and 1 month after repositioning. (Here, 0, 45, and 90° refer to the angle which the center axis of head deviates from the gravity line.). SVV0 SVH0°, and SVV of DUC at 120 and 180°/s 0 significantly differed between BPPV and NC group before repositioning. The deviations in SVV45, SVV90, SVH45, SVH90°, and SVV of DUC at 120°/s-2 and 180°/s-4.5 did not significantly differ between bilateral sides in BPPV patients before repositioning. The deviation in SVH90° was significantly lower after repositioning than before. The deviation in SVH45° was significantly higher 1 month after repositioning than before. The deviation angle of SVV of DUC at 180°/s-0 was significantly lower after repositioning than before. The vertigo VAS score of patient with BPPV continued to decrease after repositioning. Before repositioning, the otolithic organ function of BPPV patients was obviously impaired, with no significant difference between the healthy and affected ear. After repositioning, there was a transient recovery of otolithic organ dysfunction followed by a sustained decline to similar levels to before repositioning.

Forward masking in a bottlenose dolphin Tursiops truncatus: dependence on azimuthal positions of the masker and test sources.

Forward masking was investigated by the auditory evoked potentials (AEP) method in a bottlenose dolphin Tursiops truncatus using stimulation by two successive acoustic pulses (the masker and test) projected from spatially separated sources. The positions of the two sound sources either coincided with or were symmetrical relative to the head axis at azimuths from 0 to ± 90°. AEPs were recorded either from the vertex or from the lateral head surface next to the auditory meatus. In the last case, the test source was ipsilateral to the recording side, whereas the masker source was either ipsi- or contralateral. For lateral recording, AEP release from masking (recovery) was slower for the ipsi- than for the contralateral masker source position. For vertex recording, AEP recovery was equal both for the coinciding positions of the masker and test sources and for their symmetrical positions relative to the head axis. The data indicate that at higher levels of the auditory system of the dolphin, binaural convergence makes the forward masking nearly equal for ipsi- and contralateral positions of the masker and test.

Epiblast cells gather onto the anterior mesendoderm and initiate brain development without the direct involvement of the node in avian embryos: Insights from broad-field live imaging.

Live imaging of migrating and interacting cells in developing embryos has opened a new means for deciphering fundamental principles in morphogenesis and patterning, which was not possible with classic approaches of experimental embryology. In our recent study, we devised a new genetic tool to sparsely label cells with a green-fluorescent protein in the broad field of chicken embryos, enabling the analysis of cell migration during the early stages of brain development. Trajectory analysis indicated that anterior epiblast cells from a broad area gather to the head axis to form the brain primordia or brain-abutting head ectoderm. Grafting the mCherry-labeled stage (st.) 4 node in an anterior embryonic region resulted in the anterior extension of the anterior mesendoderm (AME), the precursor for the prechordal plate and anterior notochord, from the node graft at st. 5. Grafting the st. 4 node or st. 5 AME at various epiblast positions that otherwise develop into the head ectoderm caused local cell gathering to the graft-derived AME. The node was not directly associated with this local epiblast-gathering activity. The gathered anterior epiblast cells developed into secondary brain tissue consisting of consecutive brain portions, e.g., forebrain and midbrain or midbrain and hindbrain, reflecting the brain portion specificities inherent to the epiblast cells. The observations indicated the bipotentiality of all anterior epiblast cells to develop into the brain or head ectoderm. Thus, a new epiblast brain field map is proposed, allowing the reinterpretation of classical node graft data, and the role of the AME is highlighted. The new model leads to the conclusion that the node does not directly participate in brain development.

Comparison study of morphology and vascular casts between plateau-type Tibetan sheep and low-altitude small-tailed Han sheep testes.

We compared the differences in testicular morphology and vascular anatomy between plateau-type Tibetan sheep and low-altitude Small-tailed Han sheep to explore any adaptations of Tibetan sheep to high altitudes and hypoxia factors. Testicular artery architecture specimens of plateau-type Tibetan sheep and lowland Small-tailed Han sheep were used to compare the physical parameters of the testis, testicular artery architecture, arterial diameter, testicular leaflets and the characteristics of epididymal head arterioles. The results showed that the weight, major axis, minor axis, overall length, caput major axis and caput minor axis in Tibetan sheep were larger than those of Small-tailed Han sheep; however, the caput major axis of epididymal head in Tibetan sheep was smaller than that of Small-tailed Han sheep. Compared with Small-tailed Han sheep, the testicular knot-like arteries of Tibetan sheep had denser spiral distribution and more small arteries, and the diameters of centripetal arteries, knot-like arteries, centrifugal arteries and epididymal microarterioles were also thicker. The 'spindle' indentation on the surface of the microarteriole of the head of the testicular leaflets and the epididymis in plateau Tibetan sheep was relatively shallow. The results showed that the physical testicular characteristics, testicular artery construction and arteriole surface structure of Tibetan sheep were adapted for the plateau environment.

Beware of scaling artefacts and implicit model characteristics when fitting soil water release and moisture capacity data

The primary objectives of this study were to: ( i) elucidate the impacts of nonlinear scale transformations on the shapes and parameter values of soil water release and moisture capacity curves; and ( ii) demonstrate how implicit characteristics of some established soil water release and moisture capacity models can impact model-data fits and estimates of model parameters. Nonlinear scale transformations of the tension head ( h) axis (e.g., log10 h, h1/2) were found to distort release and capacity curve shapes, create fictitious curve inflections and modes, and occasionally erase visual evidence of actual inflections and modes. The popular van Genuchten–Mualem and Assouline–Grant models were shown to always generate a release curve inflection and a capacity curve mode, even when inflections and modes did not exist in the data, and this in turn caused poor model-data fits in the critical near-saturated region. The van Genuchten model with four independently fitted parameters and the Dexter–Weibull model could accurately fit data sets with no inflection or mode, but this resulted in a physically unrealistic zero-angle intersection between the release curve and the water content axis. It was concluded that nonlinear h axis transforms should not be used when determining inflections, modes, pore size distributions, soil structure parameters, or soil quality indexes from soil water release and moisture capacity data-sets. It was also recommended that more flexible release curve models should be developed that do not assume the existence of inflections and modes, and also produce physically realistic angles of intersection between the water content axis and the fitted model.

Treatment of Gravitational Pulling Sensation in Patients With Mal de Debarquement Syndrome (MdDS): A Model-Based Approach.

Perception of the spatial vertical is important for maintaining and stabilizing vertical posture during body motion. The velocity storage pathway of vestibulo-ocular reflex (VOR), which integrates vestibular, optokinetic, and proprioception in the vestibular nuclei vestibular-only (VO) neurons, has spatio-temporal properties that are defined by eigenvalues and eigenvectors of its system matrix. The yaw, pitch and roll eigenvectors are normally aligned with the spatial vertical and corresponding head axes. Misalignment of the roll eigenvector with the head axes was hypothesized to be an important contributor to the oscillating vertigo during MdDS. Based on this, a treatment protocol was developed using simultaneous horizontal opto-kinetic stimulation and head roll (OKS-VOR). This protocol was not effective in alleviating the MdDS pulling sensations. A model was developed, which shows how maladaptation of the yaw eigenvector relative to the head yaw, either forward, back, or side down, could be responsible for the pulling sensation that subjects experience. The model predicted the sometimes counter-intuitive OKS directions that would be most effective in re-adapting the yaw eigenvector to alleviate the pulling sensation in MdDS. Model predictions were consistent with the treatment of 50 patients with a gravitational pulling sensation as the dominant feature. Overall, pulling symptoms in 72% of patients were immediately alleviated after the treatment and lasted for 3 years after the treatment in 58% of patients. The treatment also alleviated the pulling sensation in patients where pulling was not the dominant feature. Thus, the OKS method has a long-lasting effect comparable to that of OKS-VOR readaptation. The study elucidates how the spatio-temporal organization of velocity storage stabilizes upright posture and how maladaptation of the yaw eigenvector generates MdDS pulling sensations. Thus, this study introduces a new way to treat gravitational pull which could be used alone or in combination with previously proposed VOR readaptation techniques.

The standing T1-L1 pelvic angle: a useful radiographic predictor of proximal junctional kyphosis in adult spinal deformity.

Proximal junctional kyphosis (PJK), which can worsen a patient's quality of life, is a common complication following the surgical treatment of adult spinal deformity (ASD). Although various radiographic parameters have been proposed to predict the occurrence of PJK, the optimal method has not been established. The present study aimed to investigate the usefulness of the T1-L1 pelvic angle in the standing position (standing TLPA) for predicting the occurrence of PJK. The authors retrospectively extracted data for patients with ASD who underwent minimum 5-level fusion to the pelvis with upper instrumented vertebra between T8 and L1. In the present study, PJK was defined as ≥ 10° progression of the proximal junctional angle or reoperation due to progressive kyphosis during 1 year of follow-up. The following parameters were analyzed on whole-spine standing radiographs: the T1-pelvic angle, conventional thoracic kyphosis (TK; T4-12), whole-thoracic TK (T1-12), and the standing TLPA (defined as the angle formed by lines extending from the center of T1 and L1 to the femoral head axis). A logistic regression analysis and a receiver operating characteristic curve analysis were performed. A total of 50 patients with ASD were enrolled (84% female; mean age 74.4 years). PJK occurred in 19 (38%) patients. Preoperatively, the PJK group showed significantly greater T1-pelvic angle (49.2° vs 34.4°), conventional TK (26.6° vs 17.6°), and standing-TLPA (30.0° vs 14.9°) values in comparison to the non-PJK group. There was no significant difference in the whole-thoracic TK between the two groups. A multivariate analysis showed that the standing TLPA and whole-thoracic TK were independent predictors of PJK. The standing TLPA had better accuracy than whole-thoracic TK (AUC 0.86 vs 0.64, p = 0.03). The optimal cutoff value of the standing TLPA was 23.0° (sensitivity 0.79, specificity 0.74). Using this cutoff value, the standing TLPA was the best predictor of PJK (OR 8.4, 95% CI 1.8-39, p = 0.007). The preoperative standing TLPA was more closely associated with the occurrence of PJK than other radiographic parameters. These results suggest that this easily measured parameter is useful for the prediction of PJK.

Live imaging of avian epiblast and anterior mesendoderm grafting reveals the complexity of cell dynamics during early brain development.

ABSTRACTDespite previous intensive investigations on epiblast cell migration in avian embryos during primitive streak development before stage (st.) 4, this migration at later stages of brain development has remained uninvestigated. By live imaging of epiblast cells sparsely labeled with green fluorescence protein, we investigated anterior epiblast cell migration to form individual brain portions. Anterior epiblast cells from a broad area migrated collectively towards the head axis during st. 5-7 at a rate of 70-110 µm/h, changing directions from diagonal to parallel and forming the brain portions and abutting head ectoderm. This analysis revised the previously published head portion precursor map in anterior epiblasts at st. 4/5. Grafting outside the brain precursor region of mCherry-expressing nodes producing anterior mesendoderm (AME) or isolated AME tissues elicited new cell migration towards ectopic AME tissues. These locally convergent cells developed into secondary brains with portions that depended on the ectopic AME position in the anterior epiblast. Thus, anterior epiblast cells are bipotent for brain/head ectoderm development with given brain portion specificities. A brain portion potential map is proposed, also accounting for previous observations.

Anterior superior iliac spine is not always reliable as a pelvic reference axis. -3D study of pelvic axis-

BackgroundThis study aims to evaluate the accuracy of the axis connecting both anterior superior iliac spines (ASIS axis) as the absolute pelvic axis. No study has ever verified the accuracy of ASIS axis particularly on the AP pelvic radiograph, which cannot be specified on it. MethodsSixty patients who underwent total knee arthroplasty and fifty patients with femoral neck fracture were recruited as subjects without hip deformities and their CT scan data were collected. We defined the line through both center of femoral heads as absolute reference axis of pelvis three-dimensionally. On the coronal plane, the errors between the femoral head axis and the axes through six pelvic landmarks in total, including ASIS were analyzed. On the axial plane, the errors of the lines through four landmarks were analyzed in the same way. Finally, on the coronal images, the mediolateral diameter of the obturator foramen and the mediolateral distance between the midline of the sacrum and the pelvic cavity were measured to evaluate bilateral symmetry of the pelvis. ResultsThe errors tended to be smaller as the axes were closer to the femoral head axis (axes connecting bilateral superior aspects of the acetabulum and the teardrops) and the ASIS axis errors were moderate. The obturator foramen based on the ASIS axis was more asymmetrical than the femoral head axis. ConclusionAdjusting the pelvic tilt and rotation, surgeons should not always rely on the ASIS and refer to appropriate, close to the hip joint references in each case.

Direction dependency in coaxial laser double wire Direct Energy Deposition

Coaxial Laser wire Direct Energy Deposition (L-DED) promises a direction-independent buildup due to a centric supply of the welding material. To fabricate Functionally Graded Materials (FGMs), a processing head was designed that is capable of supplying two wire materials into the processing zone. This study investigates the direction dependency of welding seams produced by two 1.4718 metal wires with a diameter of 0.8 mm in a coaxial laser setup using three separately controllable single laser beams with a maximum combined laser power of 660 W. The welding wires are supplied simultaneously to the laser spot under an incidence angle of 3.5° to the middle axis of the processing head. The seam geometry is investigated using a confocal laserscanning-microscope. A comparison of the height, width and macroscopic seam geometry reveals the influence of the welding direction on the seam geometry and quality in Laser Double wire Direct Energy Deposition (LD-DED).

Mathematical models of the gyrostabilizer in different modes of its operation

The article considers the development of a mathematical model of the stabilization and rotation system in the modes of stabilization, targeting, auto-tracking of the target and electrical arrest. The output signals shall be signals proportional to the components of the angular velocities of the line of sight, the angles of pitch and dash of deviation around the axes of the gyrosystem and the angles of inconsistency of the line of sight relative to the optical axis of the homing head. The system of cardan suspension of the stabilization and rotation system is considered, where the actuators are located on the axes of rotation of the outer and inner frames of the cardan suspension. The homing head is mounted on the inner frame. The inner frame is a gyrostabilized platform. Depending on the mode of operation of the stabilization and rotation system: in the stabilization mode, the coordinate system that is stabilized is assumed to be stationary in inertial space; in the auto-tracking mode of the target, the coordinate system that is stabilized by Oxyz is returned according to the change of direction to the target; in the mode of electrical locking, the axes of the coordinate system which is stabilized by Oxyz coincide with the axes of Oxoyozo connected to the body of the main product. To obtain differential equations, the projections of the total vector of the kinetic moment of the inner and outer frames on the axis of the outer frame are taken and written according to the theorem on the change of the kinetic moment of the considered system relative to the axes of suspensions. The total moments of external forces applied to the outer and inner frames around their axes of rotation, which have the following components: moments of actuators, moments of viscous and dry friction, imbalance and other unaccounted for factors around the axes of the outer and inner frames . The moments of the forces of viscous and dry friction are presented in the classical form, taking into account the signs when changing the direction of movement. The mass of the inner frame with all devices mounted on it, and the mass of the entire movable system (outer and inner frames), as well as the radius vector characterizing the displacement of the center of mass, give a static imbalance of the movable system relative to the suspension axis of the i-th frame are components imbalance. The scientific novelty of the work is to obtain a mathematical model for a particular product, as well as the practical feasibility of their application. The result is a differential equation that fully describes this system of stabilization and rotation, takes into account the parameters of actuators, turbulent moments, as well as random effects and can be used depending on the tasks.

Fresh Water Aquatic Training in Patients with Upright Posture Maintaining Disorders

The use of the fresh water aquatic training course, as a more gentle training method, may allow patients to ensure effective restoration of muscle functions responsible for maintaining an upright body position. A more accurate control of the course results can be performed using a virtual analysis carried out using the «Habilect» system that allows to determine the body parts attitude. Aim. To study the effect of training in fresh water using the Habilect system based on the Microsoft Kinect infrared sensor (video stabilometry) on motor functions that contribute to maintaining an upright body posture in patients with mild gait disturbances. Material and methods. An open descriptive study was conducted including 12 patients (7 men, 5 women), aged 40 to 62 years, with upright posture maintaining disorders, which correspond to the functional diagnosis encoded by the ICF «Gait Stereotype Functions» B770.1 – mild violations (5–24%). A group of subjects (n = 12), in addition to basic therapy and training with an exercise therapy instructor, underwent aquatic training in fresh water for two weeks (30 minutes, 6 days a week). Assessment methods: the research was carried out using the Habilect gait video analysis system before and after the rehabilitation course. The χ2 test was used to assess the significance of differences between groups of qualitative variables. When analyzing quantitative variables, the Shapiro-Wilk’s (W) test was performed. For abnormal distribution, the data is in Me format [Q25-Q75]. The Wilcoxon T-test was used to assess the significance of differences in quantitative variables of the two studied groups. The processing of the obtained research results was carried out using the Statistica for Windows, v. 8.0 (StatSoft Inc., USA) and Microsoft Excel (Microsoft, USA). The significance of the differences was considered established at p <0.05. Result and discussion. When examining the amplitude of body deflection along the X-axis before training, they were 3.25 cm [-98 cm; 93.9 cm], after – -9.96 cm [-100.92 cm; -81.96 cm], on the Y-axis before training – -29.01 cm [-29.01 cm; 13.76 cm], after –-30.59 cm [-30.59 cm; 31.09 cm], on the Z-axis before training – 388.1 cm [369.22 cm; 393.39 cm], after training – 380.96 cm [377.98cm, 400.05 cm], deviation of the body movement vector before training 16.45 cm [7.46 cm; 338.67 cm], after training – 324.7 cm [324.7 cm; 342.56 cm]. When examining the amplitude of head deflection along the X-axis before training, they were -0.92 cm [-1.24 cm; -0.92 cm], after – 1.5 cm [-10.19 cm; 2.38 cm], Y-axis before training – 125.33 cm [61.13 cm; 128.94 cm], after – 107.42 cm [52.49 cm; 107.42 cm], along the Z-axis before training – -8.59 cm [-8.97 cm; -5.33 cm], after training – -14.89 cm [-14.89 cm, -3.45cm]. When calculating the increase in deviation (deviations of the main body axes from the initial value) using the Wilcoxon T-test revealed statistically significant deviations in the X-axis (an increase of 306.5%, p = 0.0504), the Z-axis (an increase of 112.68%, p =0.0225) and the Body Angle parameter (an increase of 1973.86% p = 0.0323). When calculating the increase in the deviation of the head axes from the initial value using the Wilcoxon T-test, statistically significant deviations were revealed along the X axis (increase of 163.04%, p = 0.0280), the Y axis (increase of 85.71%, p = 0.0199) and the parameter Z (an increase of 173.34% p = 0.0292). The study revealed a decrease in the body axes deviations amplitude in all 3 planes, which indicates an improvement in the work of all brain parts that are responsible for the coordination of motor functions and their vegetative support, an improvement in functional interaction within individual muscle chains. The reduction in the head and neck muscles in compensatory balancing participation during walking and maintaining a vertical body posture mainly due to the muscles of the lower extremities and pelvis contributes to the prevention of arterial and venous circulation disorders in the head and neck and makes training not only more effective, but also safer. Conclusion. Due to the decrease in the amplitude of deviations along all three axes (Z, Y, X), the course of aquatic training contributes to the correction of upright posture maintaining disorders, a statistically significant decrease in the amplitude of head and neck movements.

Fine structure formation in rails under ultra long-term operation

By the methods of transmission electron microscopy (TEM) at micro- and nanoscale levels the quantitative transformations of structure at a depth of 0, 2, 5, 10 mm along central axis and symmetry axis of fillet head of lengthy differentially quenched rails after severe plastic deformation (passed tonnage of 1770 mln. gross tons) are revealed. At a microscale level the transformation of cementite plates by newly formed grain boundaries absorption of carbon atoms from bulk carbides is established. At a nanoscale level the subgrain structure, being formed in surface layers, contains cementite nanodimensional particles, localized in junctions and along subgrain boundaries. This type of structure was formed as a result of dynamic recrystallization under megaplastic deformation being realized in a process of extremely long-term service of rails. The formation of so-called ‘channels of deformation’ is determined. It is shown that scalar and excess dislocation density in ferrite constituent of steel structure increases as the rail head surface is approached.

Digital analysis of external fixation area of proximal humerus fractures in elderly patients

IntroductionThe purpose is based on anatomical basis, combined with three-dimensional measurement, to guide the clinical repositioning of proximal humeral fractures, select the appropriate pin entry point and angle, and simulate surgery.Methods11 fresh cadaveric specimens were collected, the distance of the marked points around the shoulder joint was measured anatomically, and the vertical distance between the inferior border of the acromion and the superior border of the axillary nerve, the vertical distance between the apex of the humeral head and the superior border of the axillary nerve, the vertical distance between the inferior border of the acromion and the superior border of the anterior rotator humeral artery, and the vertical distance between the apex of the humeral head and the superior border of the anterior rotator humeral artery were marked on the 3D model based on the anatomical data to find the relative safety zone for pin placement.ResultsContralateral data can be used to guide the repositioning and fixation of that side of the proximal humerus fracture, and uniform data cannot be used between male and female patients. For lateral pining, the distance of the inferior border of the acromion from the axillary nerve (5.90 ± 0.43) cm, range (5.3-6.9) cm, was selected for pining along the medial axis of the humeral head, close to the medial cervical cortex, and the pining angle was measured in the coronal plane (42.84 ± 2.45)°, range (37.02° ~ 46.31°), and in the sagittal plane (28.24 ± 2.25)°, range (19.22° ~ 28.51°). The pin was advanced laterally in front of the same level of the lateral approach point to form a cross-fixed support with the lateral pin, and the pin angle was measured in the coronal plane (36.14 ± 1.75)°, range (30.32° ~ 39.61°), and in the sagittal plane (28.64 ± 1.37)°, range (22.82° ~ 32.11°). Two pins were taken at the greater humeral tuberosity for fixation, with the proximal pin at an angle (159.26 ± 1.98) to the coronal surface of the humeral stem, range (155.79° ~ 165.08°), and the sagittal angle (161.76 ± 2.15)°, with the pin end between the superior surface of the humeral talus and the inferior surface of the humeral talus. The distal needle of the greater humeral tuberosity was parallel to the proximal approach trajectory, and the needle end was on the inferior surface of the humeral talus.ConclusionBased on the anatomical data, we can accurately identify the corresponding bony structures of the proximal humerus and mark the location of the pin on the 3D model for pin placement, which is simple and practical to meet the relevant individual parameters.

O-149 Evaluation of structural problems in the application of strict criteria for sperm morphology assessment

Abstract Study question Which criteria, described by WHO 2010, cause most problems during sperm morphology assessment and lead to outcome variation in a national external quality control program? Summary answer Assessment of head ovality, regularly contoured head, regularly contoured midpiece and alignment of major axis of midpiece and head lead to the most variation. What is known already Morphology assessment of spermatozoa is known as a rather difficult part of semen analysis. Over the past 40 years, morphological criteria became stricter and reference values changed significantly, leading to a 4% lower reference value for normal/typical morphology in 2010. This has consequences for the statistical power of the analysis. Moreover, many laboratories do not use the staining method as advised by the WHO and are getting stricter and stricter in the application of the criteria. Improvement of the assay is therefore necessary. In this study, as a first step, variation in the use of the strict criteria is evaluated. Study design, size, duration Data from the Dutch external quality control (EQC) program were evaluated in this retrospective study over the period 2015 – 2020. The program consists of four rounds per year and includes the assessment of three photos of Papanicolaou stained spermatozoa. These spermatozoa were dichotomously judged (normal/abnormal) on 14 morphological criteria (WHO manual, 2010). Consensus results of three experts served as reference. In total, variation over results of 72 photos (1008 values) was analysed. Participants/materials, setting, methods Participants were staff members from Dutch laboratories (1 member per lab per round) that perform semen analysis. The outcomes of the participants were tested for variation per criterion, both over the entire 6-year period and for trends during this period. To gain insight in the influence of “time”, three photos were provided three times (in 2015/2018/2020) and six photos were provided twice (in 2016/2018 and 2018/2020). Setup was blinded to both participants and experts. Main results and the role of chance In the period 2015 – 2020, 88 – 103 laboratories participated in the EQC program. Of these laboratories, 40 – 60 took part in the photo evaluation. Variation per criterion was expressed in categories green, orange and red, with resp. >90%, 60-90% and <60% agreement between the participants. Overall, variation was in 57% in category green, 37% orange and 6% red. Head ovality, regularity of head contours, regularity of midpiece contours and alignment of the major axis of midpiece and head lead to the most variation. For these criteria, resp. 14, 17, 10 and 17% were in the category red and resp. 50, 47, 71 and 64% in category orange. Lowest variation was found for acrosomal vacuoles, excessive residual cytoplasm, tail thickness and tail length with resp. 76, 77, 94, 85% in category green. Trend analysis lead to similar conclusions: most criteria show a slightly positive trend, but head ovality and regularity of head and midpiece show a stable or declining trend. Three photos were used in three rounds and six photos in two rounds. In 26 (8.8%) cases, shifts towards higher (5) or lower (21) variation were found. Experts changed their opinion in 3 (1%) cases. Limitations, reasons for caution Results are dependent on the morphology of the spermatozoa (magnitude of abnormalities) and of the photo quality. Wider implications of the findings The definitions of the criteria need to be better explained and trained, especially for ovality of the head, regularity of the midpiece and overlap of the longitudinal axes of midpiece and head. Moreover, explanation of the criteria in the light of physiology will probably lead to better evaluations by participants. Trial registration number Not Applicable

Influence of the Undercut Anchor Head Angle on the Propagation of the Failure Zone of the Rock Medium.

The paper presents the results of a numerical analysis (FEM) describing the effect of the undercutting head angle on the formation of the rock mass failure zone during the initial stages of failure propagation. The research was carried out in the context of developing a technology for rock extraction by controlled pull-out of undercut anchors installed in the rock mass. The focus was on the initial stage of crack propagation and its trajectory for anchors embedded at an assumed constant depth and a value of the friction coefficient of the rock against the anchor head. It is shown that smaller angles favor smaller stripping angles and an increased radial impact of the head on the rock material (in the plane perpendicular to the head axis), while the impact of heads with larger angles is found to favor larger fracture penetration angles and faster penetration towards the free rock surface.

Optimization design of O-ring linear accelerator gantry and mechanical isocenter detection method.

With the development of the precise radiotherapy, the accuracy of radiotherapy equipment is gradually improved. The gantry, the carrier of the treatment head and various testing devices, is the most important component that determines the accuracy of the entire equipment. In this paper, the layout of the O-ring linear accelerator and the structure of the gantry are optimized to reduce the weight of the gantry by 50% and the moment of inertia by 60%. A mechanical isocenter detection method based on the laser tracker is proposed to conduct a rapid and accurate isocenter measurement for the optimized gantry. The experimental results show that the maximum deformation of the optimized gantry under load is 0.13mm during rotation and the maximum intersection distance between the gantry axis and the treatment head axis at the isocenter position is 0.21mm.

Evaluation of acromial spur using ultrasonography.

BackgroundThe presence of an acromial spur implies a rotator cuff disorder due to impingement between the acromial spur and the rotator cuff. The purpose of the study was to observe acromial spurs using ultrasonography and to compare measurements between plain radiographs and sonograms.MethodsWe retrospectively enrolled 51 consecutive patients with acromial spurs, which were interpreted on preoperative plain radiographs (supraspinatus outlet view and 30° caudal tilt) and preoperative sonograms. The ultrasonography transducer was held vertically and continuously moved laterally, which corresponded to the long axis of the long head of the biceps. The distance from the most distal margin of the original acromion to the most projected point of the acromial spur was measured.ResultsNo significant difference was found between the plain radiograph and ultrasonography measurements (p=0.186). A moderate to strong correlation was detected between the ultrasonography and supraspinatus outlet-view measurements (r=0.776, p=0.000).Conclusions Anteriorly projected acromial spurs were well-visualized by ultrasonography. No discrepancy in acromial spur length was detected between the use of plain radiography (supraspinatus outlet view and 30° caudal-tilt view) and ultrasonography. The correlation coefficients between the plain radiography and ultrasonography measurements exceeded 0.7.

Is Combined Anteversion Equally Affected by Acetabular Cup and Femoral Stem Anteversion?

BackgroundTo create a safe zone, an understanding of the combined femoral and acetabular mating during hip motion is required. We investigated the position of the femoral head inside the acetabular liner during simulated hip motion. We hypothesized that cup and stem anteversions do not equally affect hip motion and combined hip anteversion. MethodsHip implant motion was simulated in standing, sitting, sit-to-stand, bending forward, squatting, and pivoting positions using the MATLAB software. A line passing through the center of the stem neck and the center of the prosthetic head exits at the polar axis (PA) of the prosthetic head. When the prosthetic head and liner are parallel, the PA faces the center of the liner (PA position = 0, 0). By simulating hip motion in 1-degree increments, the maximum distance of the PA from the liner center and the direction of its movement were measured (polar coordination system). ResultsThe effect of modifying cup and stem anteversion on the direction and distance of the PA’s change inside the acetabular liner was different. Stem anteversion influenced the PA position inside the liner more than cup anteversion during sitting, sit-to-stand, squatting, and bending forward (P = .0001). This effect was evident even when comparing stems with different neck angles (P = .0001). ConclusionCup anteversion, stem anteversion, and stem neck-shaft angle affected the PA position inside the liner and combined anteversion in different ways. Thus, focusing on cup orientation alone when assessing hip motion during different daily activities is inadequate.

Which way is down? Visual and tactile verticality perception in expert dancers and non-experts

Gravity provides an absolute verticality reference for all spatial perception, allowing us to move within and interact effectively with our world. Bayesian inference models explain verticality perception as a combination of online sensory cues with a prior prediction that the head is usually upright. Until now, these Bayesian models have been formulated for judgements of the perceived orientation of visual stimuli. Here, we investigated whether judgements of the verticality of tactile stimuli follow a similar pattern of Bayesian perceptual inference. We also explored whether verticality perception is affected by the postural and balance expertise of dancers. We tested both the subjective visual vertical (SVV) and the subjective tactile vertical (STV) in ballet dancers and non-dancers. A robotic arm traced downward-moving visual or tactile stimuli in separate blocks while participants held their head either upright or tilted 30° to their right. Participants reported whether these stimuli deviated to the left (clockwise) or right (anti-clockwise) of the gravitational vertical. Tilting the head biased the SVV away from the longitudinal head axis (the classical E-effect), consistent with a failure to compensate for the vestibulo-ocular counter-roll reflex. On the contrary, tilting the head biased the STV toward the longitudinal head axis (the classical A-effect), consistent with a strong upright head prior. Critically, tilting the head reduced the precision of verticality perception, particularly for ballet dancers’ STV judgements. Head tilt is thought to increase vestibular noise, so ballet dancers seem to be surprisingly susceptible to degradation of vestibular inputs, giving them an inappropriately high weighting in verticality judgements.