Angular Parameters Research Articles

CORRELATIONS BETWEEN SKELETAL ANGULAR INDICATORS OF THE JAWS, CHARACTERISTICS OF INCISAL POSITION AND PROFILE OF SOFT FACIAL TISSUES IN ORTHODONTIC PATIENTS

Assessment of a face in profile is an integral part of a complete orthodontic diagnosis. The degree of labial inclination of the axes of the incisal crowns in relation to cephalometric and facial indicators are particularly important elements in orthodontic treatment in order to achieve an aesthetic and natural appearance of the face. The purpose of this study is to establish the peculiarities of the correlations between the skeletal angular parameters of the jaws, the characteristics of the incisal position, and the profile of the soft facial tissues of orthodontic patients. Participants and methods. Using the Veraviewepocs 3D device, Morita (Japan), 60 patients (29 men (48.3%) and 31 women (51.7%) with various occlusal pathologies aged from 11 to 39 years underwent teleradiograms. Using the licensed program for cephalometric analysis "Audax Ceph 6.0", the following indicators were analyzed: skeletal sagittal angles SNA, SNB, ANB. Skeletal vertical angles: NL-NSL, ML-NSL, NL-ML. Dento-alveolar parameters: +1/NL, +1/NA, -1/ML, -1/NB, +1/-1. Cephalometric indicators of soft tissues and facial profile: Gl'Sn'Pog', Nasolabial angle, Ls'-E-line, Li'-E-line. Correlations were evaluated in the IBM SPSS Statistics 23 license package using Spearman's non-parametric statistics. Results and discussion. Both men and women show that the ANB angle has the largest number of correlations with dental and profilometric indicators. In both cases, the angle ANB has the highest degree of correlation with the face profile angle Gl'Sn'Pog'. In men, the level of significance of ANB to Gl'Sn'Pog' is (r=-0.796, p=0.000), for women this index is r=-0.771, p=0.000. This indicates a significant influence of skeletal pathology on the type of the profile and facial aesthetics.

Geometrical Approaches for the Accurate Identification of Normal Vertical Positions of Sella and Nasion Points in Cephalograms.

The aim of the study is to identify the normal vertical positions of sella (S) and nasion (N) points in subjects with a normal inclination of anterior cranial bases. Lateral cephalograms of 117 subjects who had a normal ∠SN-FH plane (7° ± 1°), ∠SN-palatal plane (9° ± 2°), ∠FH-palatal plane (1° ± 1°), and cranial base angles (131° ± 4°) were included in the study. Various linear and angular parameters and ratios were evaluated to determine the normal vertical positions of S and N points. An unpaired t-test was used to identify any significant differences between males and females. The P value of 0.05 was considered as the level of significance. Among subjects with the normal inclinations of SN, FH, and palatal planes and cranial base angle, the mean values of ∠Ar-S-Ptm, ∠S-Ptm-Ar, and ∠S-Ar-Ptm were 59.38° ± 3.52°, 59.70° ± 3.21°, and 60.84° ± 3.56°, respectively, forming an almost equilateral triangle between S, Ar, and Ptm points. The mean values of ∠Ba-S-PNS, ∠S-PNS-Ba, and ∠S-Ba-PNS were 59.56° ± 3.17°, 59.72° ± 3.47°, and 60.76° ± 3.11°, respectively, forming another approximate equilateral triangle between S, Ba, and PNS points. The mean S-FH to N-FH ratio was 0.67 ± 0.06% for the whole sample, but it was significantly greater in males (0.69 ± 0.07%) compared to females (0.65 ± 0.06%) (P=0.002). Two approximate equilateral triangles were formed between S, Ar, and Ptm points; and S, Ba, and PNS points in subjects with normal inclinations of SN, FH, and palatal planes and cranial base angle. The S-FH to N-FH ratio was an excellent guide to locating the normal vertical position of S and N points.

Inhibition Mechanism of EMIM-Cl to Methane Gas Hydrate by Molecular Dynamics Simulation

Deep-water gas well testing is a key technology for obtaining reservoir production and physical property parameters. However, gas hydrates could easily form and cause blockage in the low-temperature and high-pressure environment on the seafloor. Therefore, it is extremely important to inhibit hydrate growth in deep-water operations. Ionic liquid is a type of hydrate inhibitor with both thermodynamic and kinetic effects. However, its intrinsic inhibiting mechanism is still unclear. By using molecular dynamics simulation, the growth process of methane hydrate in the 1-ethyl-3-methylimidazole chloride (EMIM-Cl)-containing system at the pressure of 15 MPa and temperature of 273.15 K was studied. The system energy and angular order parameters (AOP) were extracted as the evaluation indicators. It was found that the time for the complete growth of methane hydrate in the EMIM-Cl-containing system was about 10 ns, longer than that in the pure water, indicating that EMIM-Cl showed an obvious inhibition effect to hydrate growth. The results also implied that the joint action of hydrogen bond and steric hindrance might be the inhibition mechanism of EMIM-Cl. Some six-membered rings in hydrate crystal large cage structures evolved from five-membered rings under the effect of EMIM, which partly contributed to the delay of hydrate formation.

Combining Azimuthal and Polar Angle Resolved Shadow Mask Deposition and Nanosphere Lithography to Uncover Unique Nano-Crystals.

In this article, we present a systematic investigation on a multistep nanosphere lithography technique to uncover its potential in fabricating a wide range of two- and three-dimensional nanostructures. A tilted (polar angle) electron beam shower on a nanosphere mask results in an angled shadow mask deposition. The shape of the shadow also depends on the azimuthal angle of the mask sitting on top of the substrate. We performed angled shadow mask depositions with systematic variation of these two angular parameters, giving rise to complex nanostructures (down to 50 nm), repeated over a large area without defect. In this article, nanosphere lithography with two- and four-fold azimuthal symmetry was studied at constant tilt angles followed by variations in tilt without azimuthal rotation of the substrate. Finally, both angular parameters were simultaneously varied. The structure of shadow crystals was explained using Matlab simulation. This work stretches the horizons of nanosphere lithography, opening up new scopes in plasmonic and magnonic research.

Stiffness evaluation of a novel ankle rehabilitation exoskeleton with a type-variable constraint

This paper presents a novel ankle rehabilitation exoskeleton with two rotational degrees of freedom, which is suitable for dynamical rehabilitation for patients with neurological impairments. Its stiffness performance is assessed in consideration that the interaction between the footplate and the ground may deflect the mechanism away from the desired/predefined motion patterns. The novel design employs a universal-prismatic-universal (U-P-U) joint link, whose constraint type changes between a couple and a line vector during manipulation of the exoskeleton. To conduct a stiffness analysis of such a mechanism with a type-variable constraint – for the first time – a modified screw-based method (SBM) is proposed. Comparisons with the results obtained from finite element analysis verified that, the modified SBM provides reliable estimates of the exoskeleton's stiffness within the complete workspace (covering the constraint-type transition configurations). The stiffness of the exoskeleton is further evaluated by acquiring the minimum/maximum stiffness values, after computing the distribution of the most crucial linear and angular stiffness parameters within the workspace. Moreover, the influence of the architectural parameters on the stiffness properties is considered for further design optimization.

New analysis and classiŢcation of Angle’s class II malocclusion varieties during the mixed dentition period

Introduction: It is well known that Angle's class II malocclusion is the most common of all occlusal pathology. The prevalence of this malocclusion among children remains at 35-43% and tends to increase. Class II malocclusion negatively affects not only the functions of chewing, swallowing, breathing and speech, but also life in general, especially for children and adolescents. An analysis of modern scientific papers shows that variability of class II malocclusion is insufficiently covered in published classifications.
 Objectives: To develop a classification of Angle's class II malocclusion forms based on the determination of angular and linear cephalometric parameters for children aged 7 to 12 years old and to analyze of their prevalence in Ukraine.
 Material and Methods: 138 lateral cephalometric radiographs of children aged 7 to 12 years old with Angle's class II malocclusion were selected. Cephalometric analysis by Perillo-ID method was performed on all 138 radiographs. 68 lateral cephalometric radiographs were selected for further study.
 Results: Cephalometric analysis by Perillo-ID method on 68 lateral cephalograms in children aged 7-12 years old showed a wide range of variability forms of Angle's class II malocclusion. The results of 7 angular and 4 linear parameters allowed to create a classification of Angle's class II malocclusion forms and sizes, taking into consideration the position of the lower jaw in children during the mixed dentition period.
 Conclusions: Authors modified Perillo's cephalometric analysis, which allowed to create a detailed classification of Angle's class II malocclusion forms for children during the mixed dentition period. The new classification will allow to clearly differentiate the etiology of malocclusion, to differentiate the true mandible underdevelopment from its retroposition or rotation.

Upper limb movement during locomotion in patients with neurological disorders: a wearable-based approach

The contribution of upper limbs during walking is crucial in maintaining balance and stability: humans, in fact, swing each upper limb in phase with contra-lateral lower limb at their comfortable walking speed, with a ratio of 1:1 [1], thus counteracting the angular momentum, reducing the energy expenditure, and improving the overall gait efficiency [2,3]. In people who suffer from neurological disorders, like Multiple Sclerosis (MS) or Traumatic Brain Injury (TBI), upper limb function is often impaired, resulting in differences in arm swing frequency, amplitude, symmetry, as well as in the ratio between step and arm swing frequency, compared to healthy people [2]. Although it is known that a neurological rehabilitation program should focus on the recovery of a proper gait also emphasizing the contribution of upper limbs [1], few studies analyzed the contribution of the upper arms during locomotion in people with neurological disorders. The aim of this study is to explore a wearable sensor-based protocol for the assessment of the upper limb movement in patients with MS and TBI compared to healthy participants. Thirty-three patients suffering from MS (24 F; 49.8±9.3 y; EDSS 4.0±1.6), 8 patients suffering from TBI (2 F; 32.3±14.1 y; DGI 18.3±5.9), and 20 healthy adults (HC) (9 F; 37.0±19.9 y) were enrolled in this study (CE/PROG.700). Each participant performed a 10-meter Walking Test (10mWT) while wearing 5 synchronized inertial measurement units (IMUs) located at sternum, both wrists and distal tibiae level. Stride segmentation was performed using tibiae-mounted IMUs and the following parameters were estimated from wrist- and sternum-mounted IMUs [4]: arm oscillation frequency, peak and range of the angular velocity norm, as well as step to arm oscillation frequency ratio for the right (RW) and left (LW) wrists (freq, gyro peak, gyro range, Step-freq ratio). The range of the sternum cranio-caudal angular velocity was also obtained (sternum gyro range), together with a measure of symmetry (Symmetry Index [5]) between RW and LW angular velocity ranges. After checking for data normality, a one-way ANOVA was used to test for significant differences among MS, TBI, and HC. Post-hoc analysis was performed using Bonferroni-Holmes correction for multiple comparisons. Results are depicted in Fig. 1 (the larger the spider, the better the performance). Significant differences were found in frequency, symmetry, and angular velocity parameters among the MS, TBI, and HC. Patients with TBI seem to be characterized by a reduced performance with respect to MS, except for the step to arm swing ratio. The proposed assessment protocol demonstrates a potential clinical value in discriminating not only patients with neurological disorders from HC, but also patients with MS from TBI, who showed significant differences in terms of swing frequency, angular velocity range, and symmetry. This information could be useful in tailoring rehabilitation treatments involving the upper limbs during gait exercises [1]. Although in the present study, no significant difference was found among the three populations walking speed, the effect of the latter on the proposed metrics should be better investigated in further studies.

Morphometric evaluation of sella turcica and cranial base in patients with congenital absence of teeth.

To evaluate the size and shape of sella turcica and cranial base in patients with different degrees of congenital absence of teeth. The subjects comprised 322 patients from the Department of Orthodontics, West China Hospital of Stomatology, Sichuan University from 2020 to 2021. Based on the number of congenital absence of teeth, the patients were divided into three groups: control group (without loss of teeth, n=112), group Ⅰ (loss of 1-2 teeth, n=104), and group Ⅱ (loss of 3 or more teeth, n=106). Uceph cephalometric software was used to measure the linear and angular parameters of cranial base. The length, depth, and diameter of sella turcica were also calculated. The shape of sella turcica was described as normal or with aberrations. Analysis of variance, Kruskal-Wallis H test, chi-square test, and Fisher's exact test were conducted with SPSS 21.0. No statistical differences were observed in the length, depth, and diameter of sella turcica and parameters related to the cranial base among the three groups (P>0.05). The incidence of sella turcica bridge among the three groups was statistically significant (P=0.013). The incidence was higher in the study group compared with the control group (P<0.05), and no significant difference was observed between groups Ⅰ and Ⅱ (P>0.05). Although the linear size of sella turcica and parameters related to the cranial base was not statistically different between normal subjects and patients with congenital absence of teeth, the incidence of sella turcica bridge was higher in patients with congenital absence of teeth, suggesting the possibly abnormal anatomical morphology of sella turcica in this population.

Влияние пространственного размещения деревьев на плантациях на технологические параметры выборочных рубок

The analysis of the spatial distribution of planting material in different regions during plantation forestry in the context of the geometric parameters of the forest stand is presented, a scheme for growing and harvesting timber on plantations is proposed, the parameters of the forest stand are identified that affect the harmless selective felling of individual trees left for rearing, the possibility is substantiated the use of logging machines in the existing formats of plantations, the requirements for the results of each stage of forest cultivation are formulated, the patented methodology and calculations of the average linear and angular parameters of selective felling are given.

Tensor of Order Two and Geometric Properties of 2D Metric Space

A 2D metric space has a limited number of properties through which it can be described. This metric space may comprise objects such as a scalar, a vector, and a rank-2 tensor. The paper provides a comprehensive description of relations between objects in 2D space using the matrix product of vectors, geometric product, and dot product of complex numbers. These relations are also an integral part of the Lagrange’s identity. The entire structure of derived theoretical relationships describing properties of 2D space draws on the Lagrange’s identity. The description of how geometric algebra and tensor calculus are interconnected is given here in a comprehensive and essentially clear manner, which is the main contribution of this paper. A new term in this regard is the total geometric and matrix product, which—in a simple manner—predetermines and defines the existence of differential relations such as the gradient, the divergence, and the curl of a vector field. In addition, geometric interpretation of tensors is pointed out, expressed through angular parameters known from the literature as a tensor glyph. This angular interpretation of the tensor has an unequivocal analytical form, and the paper shows how it is linked to the classical tensor denoted by indices.

Closed-form solutions for attenuation peaks and band boundaries of general monocoupled systems

The unit cells connected periodically at a single node with only one degree of freedom is called a monocoupled system. Dispersion relations for such systems are studied widely; however, the analytical solution for salient features of the attenuation band, such as the number of peaks in a band and band merging, have been relatively unexplored. In this paper, a general theory for obtaining the attenuation characteristics of the general monocoupled system from the roots and poles of the rational polynomial of the dispersion relation is developed. The uniqueness of the developed rational polynomial method is that it can predict the attenuation peaks and the possibility of multiple peaks in an attenuation band due to coupling between the different band formation mechanisms in addition to standard band boundaries. The most general monocoupled system has been conceptualized by combining the three mechanisms, namely inertial amplifier, effective negative mass, and effective negative stiffness. This general system is named Inertial Amplifier Negative Mass Negative Stiffness (IANMNS). This designed monocoupled system degenerates into other seven subsystems as special cases, such as the Inertial Amplifier Negative Stiffness (IANS), the Inertial Amplifier Negative Mass (IANM), the Negative Mass Negative Stiffness (NMNS), the Inertial Amplifier (IA), the Negative Stiffness (NS), the Negative Mass (NM) and the Monoatomic system. The closed-form expressions for the peaks in attenuation level and bounds in terms of nondimensional frequency ratio and other governing parameters such as the inertial mass ratio, mass ratios of resonators one (embedded in main chain mass) and two (embedded in inertial mass), frequency ratios of resonators one and two, and angular parameter are derived for the IANMNS and all the other seven subsystems. The conditions for obtaining the double peaks and band merging are defined analytically.

Reliability of wearable sensors-based parameters for the assessment of knee stability.

Anterior cruciate ligament (ACL) rupture represents one of the most recurrent knee injuries in soccer players. To allow a safe return to sport after ACL reconstruction, standardised and reliable procedures/criteria are needed. In this context, wearable sensors are gaining momentum as they allow obtaining objective information during sport-specific and in-the-field tasks. This paper aims at proposing a sensor-based protocol for the assessment of knee stability and at quantifying its reliability. Seventeen soccer players performed a single leg squat and a cross over hop test. Each participant was equipped with two magnetic-inertial measurement units located on the tibia and foot. Parameters related to the knee stability were obtained from linear acceleration and angular velocity signals. The intraclass correlation coefficient (ICC) and minimum detectable change (MDC) were calculated to evaluate each parameter reliability. The ICC ranged from 0.29 to 0.84 according to the considered parameter. Specifically, angular velocity-based parameters proved to be more reliable than acceleration-based counterparts, particularly in the cross over hop test (average ICC values of 0.46 and 0.63 for acceleration- and angular velocity-based parameters, respectively). An exception was represented, in the single leg squat, by parameters extracted from the acceleration trajectory on the tibial transverse plane (0.60≤ICC≤0.76), which can be considered as promising candidates for ACL injury risk assessment. Overall, greater ICC values were found for the dominant limb, with respect to the non-dominant one (average ICC: 0.64 and 0.53, respectively). Interestingly, this between-limb difference in variability was not always mirrored by LSI results. MDC values provide useful information in the perspective of applying the proposed protocol on athletes with ACL reconstruction. Thus, The outcome of this study sets the basis for the definition of reliable and objective criteria for return to sport clearance after ACL injury.

Development of an FEA program with full-size stiffness and mass matrices for dynamic analysis of high-rise buildings: A comparison with SAP2000

Computational methods used for estimation the effects of dynamic loading on buildings need to be developed and updated to ensure structural safety. A computer program, YAY2020-Dynamic was developed using the Matlab interpreter to calculate the effect of dynamic forces on planar structures. The program successfully estimated the impact of dynamic forces on structures. The main feature of the program is that it uses mass and stiffness matrices with both diagonal and non-diagonal elements. Furthermore, the developed program uses 12 × 12 matrices in shear formulations to include moment and rotation effects perpendicular to the plane. These features were not used in the literature and have not been studied on high-rise buildings before. Modal analysis (Eigen analysis) and time history analysis (Newmark analysis) are performed in the program for dynamic analysis of high-rise buildings. A special formulation is used to include angular and rotation freedom parameters in the mass and stiffness matrices of plate elements. These matrices were presented for the first time in this study as 12 × 12 matrices with diagonal and non-diagonal elements. The core principle of the program is to make more realistic modeling by considering as many mechanisms as possible, instead of making assumptions and neglecting some parameters that limit representing real behavior. To determine the performance of the developed program, two buildings (a 10-story and a 20-story) were examined. According to the results, YAY2020-Dynamic determined that the examined building models were more rigid and had fewer deformations than the estimated by SAP2000. Therefore, the use of YAY2020-Dynamic in design stages can help determine the required member strengths more precisely and choose the proper building materials while considering the safety factors.

Charged and rotating multi-black holes in an external gravitational field

We construct analytical and regular solutions in four-dimensional General Relativity which represent multi-black hole systems immersed in external gravitational field configurations. The external field background is composed by an infinite multipolar expansion, which allows to regularise the conical singularities of an array of collinear static black holes. A stationary rotating generalisation is achieved by adding independent angular momenta and NUT parameters to each source of the binary configuration. Moreover, a charged extension of the binary black hole system at equilibrium is generated. Finally, we show that the binary Majumdar–Papapetrou solution is consistently recovered in the vanishing external field limit. All of these solutions reach an equilibrium state due to the external gravitational field only, avoiding in this way the presence of any string or strut defect.

EVALUATION OF ATTRACTIVE FACIAL PROFILE IN DIFFERENT DENTOFACIAL IRREGULARITIES (ANGLE'S) IN BENGALI POPULATION USING PHOTOGRAPHIC MEASUREMENTS

Introduction: Attractive facial profile is significant to each individual. Nowadays, however, establishing ideal facial esthetics is also a major factor in Orthodontic treatment. Achieving the class l occlusion is not the only benchmark for success, but also the resultant soft tissue contours are often equally important in defining a well- treated case. The study was done to determine the type of malocclusions that is more coherent to facial attractiveness as well as to establish soft tissue profile norms for Bengali population using linear and angular photogrammetric analysis. Materials and Methods: 80 samples of age group ranging from 12 to 25 years were selected from the patient reported in Dr R Ahmed Dental College and Hospital, Department of Orthodontics and Dentofacial Orthopaedics west Bengal. Standard frontal and lateral profile photographs were taken and on each photograph, all the linear and angular measurements were statistically analyzed. Seven linear and six angular soft tissue parameters were calculated. Correlation coefficient was carried out between linear, angular measurements and VAS score of different malocclusion. The following inferences were obtained from the study regarding the linear, angular parameters and VAS score of Bengali population. Results: ANOVA showed that there was significant difference between mean VAS of the four different type of malocclusion. As per post hoc Tukey's test mean VAS of Class-I and Class-II Div2 were significantly higher than other two classes. Conclusion: The finding of the present study showed that during Orthodontic treatment planning for Bengali subjects; it may be useful to use a modified set of norms.

SIS-BAM Algorithm for Angular Parameter Estimation of 2-D Incoherently Distributed Sources

For two-dimensional (2-D) incoherently distributed sources, this paper presents an effective angular parameter estimation method based on shift invariant structure (SIS) of the beamspace array manifold (BAM), named as SIS-BAM algorithm. In the proposed method, a shift invariance structure of the observed vectors is established utilizing a generalized array manifold of a uniform linear orthogonal array. Then, based on Fourier basis vectors and the SIS, a beamspace transformation matrix can be obtained. It projects received signals into the corresponding beamspace, so as to carry out dimension reduction of observed signals in beamspace domain. Finally, according to the SIS of beamspace observed vectors, the closed form solutions of the nominal azimuth and elevation are derived. Compared with the previous works, the presented SIS-BAM method provides better estimation performance, for example: 1) the computational complexity is reduced due to dealing with low-dimension beamspace signals and avoiding spectral search; 2) it can not only improve the angular parameter estimation accuracy but also have excellent robustness to the change of signal-to-noise ratio (SNR) and snapshot number. The theoretical analysis and simulation results confirm the effectiveness of the proposed method.

Development of a new [formula omitted]–[formula omitted] angular correlation analysis method using a symmetric ring of clover detectors

A new method for γ–γ angular correlation analysis using a symmetric ring of HPGe clover detectors is presented. Pairwise combinations of individual crystals are grouped based on the geometric properties of the spectrometer, constrained by a single variable parameterization based on symmetry considerations. The corresponding effective interaction angles between crystal pairs, as well as the attenuation coefficients are extracted directly from the measured experimental data. Angular correlation coefficients, parameter uncertainties and parameter co-variances are derived using a Monte-Carlo approach, considering all sources of statistical uncertainty. The general applicability of this approach is demonstrated by reproducing known multipole mixing ratios in 177Hf, 152Gd and 116Sn, populated by either β-decay or (n, γ)-reactions, measured at the Institut Laue-Langevin, using the EXILL&FATIMA spectrometer and different configurations of the FIPPS instrument. The derived mixing ratios are in excellent agreement with adopted literature values with comparable or better precision.

Localization and tracking of multiple fast moving targets in bistatic MIMO radar

In this paper, we propose a maximum likelihood (ML)-based scheme to accurately localize and track multiple fast-moving targets in multiple-input multiple-output (MIMO) radar systems. For the problem of tracking, the motion of the target will cause a spread spectrum effect, which broadens the beam width and skews the beam steering, rendering accurately localizing and tracking the fast moving targets extremely challenging. To tackle this problem, we use a locally linear model to approximate the real motion states of the target and define a vector to describe its motion state. As such, the motion states of targets at adjacent times can be accurately inferred within a short term based on this approximation model. To incorporate the effect of target motion when performing tracking, we estimate the motion state vector at a reference time from a batch of snapshots by using an ML estimator, instead of estimating the time-varying angular parameters directly as usual. Then the motion state vectors at other times can be inferred based on the estimated one by using the locally linear approximation model. The Cramér-Rao lower bound (CRLB) of the estimated parameters are also derived for performance evaluation. Numerical results validate the performance improvement of the proposed scheme compared to the benchmarks.

Commissioning of the St. Benedict RF carpet

The Superallowed Transition BEta NEutrino Decay Ion Coincidence Trap (St. Benedict) aims to measure the beta-neutrino angular correlation parameter for superallowed mixed beta decay transitions between mirror nuclei in order to conduct precision tests of the Standard Model. St. Benedict will include a gas catcher, a differentially pumped extraction system, a radio-frequency quadrupole (RFQ) cooler and buncher, and a Paul trap to utilize radioactive ion beams produced at the Nuclear Science Laboratory of the University of Notre Dame. The two-part differentially pumped extraction system contains a RF carpet at a helium gas pressure of around 3 mbar, and a radio-frequency quadrupole (RFQ) ion guide at a pressure of around 2×10−3 mbar. Transport efficiency of potassium ions in the first part of the extraction system using the RF carpet in the presence of gas flow was determined to be near 100% in the 0.75 to 5 mbar pressure range using the ion surfing transport method.

Ideal entry point and trajectory for C2 pedicle screw placement in children: a 3D computed tomography study.

To identify the ideal entry point for pediatric C2 pedicle screw and to obtain parameters of it for the indication of pediatric atlantoaxial fusion arthrodesis. The pediatric cervical CT images were reconstructed into the 3D digital models and the C2 vertebrae were separated. The location of ideal entry point and screw placement related linear and angular parameters were assessed on the 3D digital models. A total of 214 pedicles from 107 C2 digital models were analyzed. The average entry point for C2 was 3.80 ± 2.78mm medial to the lateral notch (LN) and 2.57 ± 1.70mm superior to the LN. The average pedicle diameter (PD) was 6.02 ± 1.31mm, and the average pedicle screw length (PSL) was 25.63 ± 3.46mm. Statistical differences were found between different sex for PD and PSL (P < 0.05). As patient age increases, using the most lateral and inferior edge of the lateral mass as a reference marker, the entry point tends to move medial and cephalad, when using the LN as a reference marker, the entry point tends to move medial and slightly caudad. Univariate linear regression analysis suggested that these linear parameters were associated with age (P < 0.01). In this study, we found that the measurement results of C2 pedicle screw varied based on sex, laterality, and ages for children younger than 18years. The entry point of the screws facilitating ideal trajectory tends to change in a linear way as a function of age. This information helps the surgeon to establish the specific anatomy related to C2 pedicle screw placement to facilitate fixation in the pediatric patients.