Types Of Curvature Research Articles

Kinematic adaptations during the sit-to-stand movement in adolescent idiopathic scoliosis with different types of curvature

Kinematic adaptations during the sit-to-stand movement in adolescent idiopathic scoliosis with different types of curvature

Theoretical and numerical study on ceiling temperature distribution of fire in the SRRT with curvature considering train blocking

The slopping rack railway tunnel (SRRT) with curvature is applied to pass through mountainous areas due to the terrain. And the temperature distribution under train blocking in the SRRT with curvature is significantly different when a fire occurs, posing a great threat to personnel safety. The train blocking and two curvature types of C-shaped and S-shaped are considered, and the mathematical expressions for temperature distribution with coefficients of slope and curvature are derived. The effects of slope, curvature, and train blocking on ceiling temperature are investigated using numerical simulation, and the applicability of the mathematical expressions is demonstrated through fitting. The results show that the mathematical expression for ceiling temperature distribution is a piecewise function with a stepped-down descent. The temperature attenuation is separated into three stages for C-shaped, and four stages for S-shaped. The coefficients are approximately linear with slope and curvature radius respectively. The train blocking on the ceiling maximum temperature for C-shaped is of a stronger effect than for S-shaped, and the slope on the temperature at the train tail for C-shaped is of a weaker effect than for S-shaped.

Layperson assessment of smile lines and upper lip combined images in smile esthetics

The esthetic assessment of smile lines by laypersons is a subject of ongoing debate. However, smile lines often appear with different types of upper lip curvature, which further complicates the esthetic assessment process, and studies on this combination are lacking. The purpose of this clinical study was to investigate a layperson's esthetic perception of smile lines and upper lip combined images. Twenty-six smile images resulting from combinations of 3 upper lip types, 4 anterior smile line types, and 3 posterior smile line types were generated by an image editing software program. Eighty-three laypersons (39 men and 44 women; 18 to 35 years of age) completed rating images using a visual analog scale. Unattractive smiles were designated to be those with scores <50 and attractive ones with scores ≥50. Data were analyzed using 1-way analysis of variance and Bonferroni post hoc tests (α=.05). High anterior smile line with gingival display >4mm obtained significantly lower scores of <50 when combined with all upper lip curvatures (upward: 28.29 ±22.79, straight: 38.74 ±23.00, downward: 30.67 ±22.25, P<.01). High anterior smile lines with gingival display ≤4mm combined with upward and straight upper lip curvature images obtained significantly higher scores, and all were ≥50 (upward: 63.24 ±22.22, straight: 61.40 ±21.58, P<.01). From a layperson's perspective, high anterior smile lines with gingival display >4mm combined with any lip type were determined to be unattractive. If gingival display was ≤4mm combined with both upward and straight lip types, the smile was assessed as attractive.

COMPARAçãO DOS PARâMETROS SAGITAIS NOS DIFERENTES TIPOS MORFOLóGICOS DA CURVATURA CERVICAL

ABSTRACT Objective: Evaluate and compare sagittal parameters of the spine in different morphological types of cervical curves. Method: ten lateral radiographs of the cervical spine of each morphological type of cervical curvature (lordotic, straightened, sigmoid and kyphotic) were used to measure the C1-C2 angle, C2-C7 angle using the Cobb method, T1 inclination, T1-lordosis inclination C2-C7 cervical and axial sagittal cervical axis. Parameter measurements were compared in the different morphological types of cervical spine curvature. Results: a statistical difference was observed in the C2-C7 angle, T1 inclination and T1 inclination-C2-C7 cervical lordosis in the different morphological types of cervical curvature. No statistical difference was observed in the C1-C2 angle and axial sagittal cervical axis in the different morphological types of cervical curvature.Conclusion: sagittal parameters (C2-C7 angle by Cobb method, T1 inclination, T1 inclination-C2-C7 cervical lordosis) present differences in the different morphological types of cervical curvatures and must be considered in the evaluation and therapeutic development. Evidence level III, retrospective comparative study.

COMPARAçãO DOS MéTODOS RADIOGRáFICOS PARA A MENSURAçãO DA CURVATURA DA COLUNA CERVICAL

ABSTRACT Objectives: Compare three methods for evaluating the curvature of the cervical spine (Cobb, Jackson and Harrison method) considering the morphological types of cervical curvature (lordotic, straightened, sigmoid and kyphotic). Method: Ten lateral radiographs of each type of cervical curvature (lordotic, rectified, sigmoid and kyphotic) were used to measure the curvature of the cervical spine using the Cobb, Jackson and Harrison methods. The results were compared. Results: he methods for assessing cervical curvature showed statistical differences in the assessment of the group of individuals and in the individualized assessment of each morphological type of cervical spine curvature. Conclusion: he methods for assessing cervical spine curvature present differences in relation to angular measurement and the difference in measurement was also observed in the different morphological types of cervical spine curvature. Evidence level III, retrospective comparative study.

Correlation of Central Corneal Thickness with Refractive Error, Corneal Curvature, and Axial Length: An Observational Study

Background: Various demographic and ocular factors influence central corneal thickness (CCT). Studies on the relationships between these parameters have shown conflicting results. We aim to investigate the correlation of CCT with different types of refractive error, axial length (AL), and corneal curvature. Materials and Methods: An observational study was undertaken in the Department of Ophthalmology, recruiting patients from 18 to 40 years of age with myopia (−0.5 D to −6 D) or hypermetropia (≤ +3 D) or emmetropia (−0.25 D to +0.25 D). All participants underwent comprehensive ophthalmic examination, including refraction, slit lamp examination and fundoscopy, followed by CCT, corneal curvature, and AL measurement. Result: A total of 1224 eyes of 612 patients (260 males and 352 females) were enrolled in the study. Out of them, 31.5% (n = 386) had emmetropia, 28.6% (n = 350) had hypermetropia, and 39.9% (n = 488) had myopia. The mean (±standard deviation [SD]) keratometry (K), CCT and AL were found to be 44.08 (±1.55) D, 528.46 (±29.78) μm, and 22.75 (±1.21) mm, respectively. With increasing age, CCT was found to be decreased (P &lt; 0.001). Compared to myopia, a significantly higher CCT was noted in hypermetropia (P &lt; 0.001). There was a negative correlation between CCT and corneal curvature among the entire study population, irrespective of their refractive status (P &lt; 0.001). This correlation was more significant among emmetropes and hypermetropes as compared to myopes. However, we found no correlation between CCT and AL in any groups. Conclusion: CCT is found to be thicker in hypermetropia and thinner in myopia as compared to emmetropia. With increasing age, the cornea tends to become steeper and thinner.

Nonlinear Vibration and Dynamic Buckling of Complex Curved Functionally Graded Graphene Panels Reinforced with Inclined Stiffeners

This paper presents a new semi-analytical approach for the nonlinear vibration and dynamic responses of functionally graded graphene platelet-reinforced composite (FG-GPLRC) panels with complex curvature reinforced by orthogonal and/or inclined stiffeners in the thermal environment resting on the nonlinear viscoelastic foundation with the nonlinearities of von Kármán in the framework of the higher-order shear deformation theory (HSDT). The three curvature types of complexly curved panels are considered to be cylindrical, sinusoid, and parabola panels. Orthogonal and/or inclined stiffeners are modeled utilizing an improved smeared stiffener technique. The stress function form is estimated by applying the like-Galerkin method for complexly curved panels. By applying the Lagrange function and Euler–Lagrange equation, the nonlinear equations of motion of the panels are obtained. The viscous damping effects of the viscoelastic foundation are considered by utilizing the Rayleigh dissipation function. Numerical results are examined utilizing the Runge–Kutta method to acquire the time-deflection curves, and by utilizing the Budiansky–Roth criterion, the critical dynamic buckling loads are determined. From the investigated results, it is possible to evaluate the nonlinear vibration and buckling dynamic responses of three forms of panels with stiffeners.

Effectiveness of Blackburn Exercise with Thoracic Extension Exercises Versus Thoracic Extension Exercise on Postural Hyper Kyphosis and Scapula Position in Young Asymptomatic Individuals - A Comparative Study

BACKGROUND: The spine is composed of two types of curvature: kyphosis and lordosis. Postural hyper kyphosis is the most common posture abnormality and can happen at any age. Causes are idiopathic, sedentary lifestyle, impairments, and aging. Abnormal posture has a detrimental effect on articular and muscular structures as it leads to muscular weakness and degenerative changes. It affects the muscular tension around the neck and shoulder; as it shifts the neck forward (muscle tightness) and the shoulder moves more internally, leading the upper back scapular muscle lengthening. This study uses a flexi-curve ruler to measure postural hyper kyphosis and lateral scapula slide test(LSST) to measure scapula distance. The Blackburn protocol is often used for shoulder and scapular impairments; in this study, the protocol is used to manage postural hyper kyphosis as it targets the same muscle groups that are in an altered state. OBJECTIVE: To compare the effect of Blackburn exercise along with thoracic extension exercise versus thoracic extension exercise on postural hyper kyphosis and scapula position in young asymptomatic individuals. METHODS: A comparative study included 70 samples, age between 18 and 28, divided into 2 groups. The degree of kyphosis was measured using a flexi curve ruler (fcr), and scapula distance was measured using a lateral scapula slide test (lsst) at three positions. Intervention was given for six weeks. RESULTS: After 6 weeks of data analysis, Group A's p-value for kyphosis angle is 0.5 and lateral scapula slide test at 0 degree is 0.735, at 45 degree is 0.1992, and at 90 degree is 0.536, showing significant improvement over another group. Conclusion: Blackburn exercises, along with thoracic extension exercises, were found to be effective in reducing the angle of kyphosis in the young population. Keywords: Hyper kyphosis, Flexi curve Ruler, LSST, Blackburn protocol.

Postbuckling analysis of externally pressured parabola, sinusoidal and cylindrical FG-GRCL panels using HSDT

In the present paper, by using the higher-order shear deformation theory and the strain-displacement relationships of large deflection, the postbuckling analysis of the functionally graded graphene-reinforced composite laminated (FG-GRCL) parabola, sinusoidal, and cylindrical externally pressured panels is presented in detail. The complex curvature functions of the parabola and sinusoidal panels are considered. The stress function is approximately determined and the Galerkin process is utilized to achieve the stability equations of nonlinear problem. The expression of pressure-deflection postbuckling behavior can be explicitly obtained. The influences of curvature types, material properties, and geometric characteristics on the postbuckling behavior of panels are also considered and investigated.

Classification of spinal curvature types using radiography images: deep learning versus classical methods.

Scoliosis is a spinal abnormality that has two types of curves (C-shaped or S-shaped). The vertebrae of the spine reach an equilibrium at different times, which makes it challenging to detect the type of curves. In addition, it may be challenging to detect curvatures due to observer bias and image quality. This paper aims to evaluate spinal deformity by automatically classifying the type of spine curvature. Automatic spinal curvature classification is performed using SVM and KNN algorithms, and pre-trained Xception and MobileNetV2 networks with SVM as the final activation function to avoid vanishing gradient. Different feature extraction methods should be used to investigate the SVM and KNN machine learning methods in detecting the curvature type. Features are extracted through the representation of radiographic images. These representations are of two groups: (i) Low-level image representation techniques such as texture features and (ii) local patch-based representations such as Bag of Words (BoW). Such features are utilized by various algorithms for classification by SVM and KNN. The feature extraction process is automated in pre-trained deep networks. In this study, 1000 anterior-posterior (AP) radiographic images of the spine were collected as a private dataset from Shafa Hospital, Tehran, Iran. The transfer learning was used due to the relatively small private dataset of anterior-posterior radiology images of the spine. Based on the results of these experiments, pre-trained deep networks were found to be approximately 10% more accurate than classical methods in classifying whether the spinal curvature is C-shaped or S-shaped. As a result of automatic feature extraction, it has been found that the pre-trained Xception and mobilenetV2 networks with SVM as the final activation function for controlling the vanishing gradient perform better than the classical machine learning methods of classification of spinal curvature types.

Update on neuromonitoring procedures applied during surgery of the spine - observational study.

Motor evoked potentials (MEPs) are currently considered as a more useful method for neurophysiological intraoperative monitoring than somatosensory evoked potentials in cases of surgery applied to patients with adolescent idiopathic scoliosis. The non-invasive approach is preferred to modify MEP recordings, criticizing, in many cases, the fundamentalism for neurophysiological monitoring based only on needle recordings. The aim of the review is to provide our own experience and practical guidelines with reference to neuromonitoring innovations. Recordings of MEPs with surface electrodes instead of needle electrodes including nerve instead of muscle combinations during neurophysiological monitoring associated with surgical interventions to the spine have become more relevant for pediatric purposes, avoiding the anesthesiology-related influences. Observations on 280 patients with Lenke A-C types of spine curvature are presented before and after the surgical correction. The MEPs recorded from nerves do not undergo fluctuations at different stages of scoliosis corrections and the anesthesia effect more than MEPs recorded from muscles. The use of non-invasive surface electrodes during neuromonitoring for MEP recordings shortens the total time of the surgical procedure without diminishing the precision of the neural transmission evaluation. The quality of MEP recordings during intraoperative neuromonitoring from muscles can be significantly influenced by the depth of anesthesia or administration of muscle relaxants but not those recorded from nerves. The proposed definition of "real-time" neuromonitoring comprises the immediate warning from a neurophysiologist about the changes in a patient's neurological status during scoliosis surgery (especially during pedicle screws' implantation, corrective rods' implantation, correction, distraction and derotation of the spine curvature) exactly during the successive steps of corrective procedures. This is possible due to the simultaneous observation of MEP recordings and a camera image of the surgical field. This procedure clearly increases safety and limits financial claims resulting from possible complications.

Bent Crystal Design and Characterization for High-Energy Physics Experiments

Bent crystal are widely used as optics for X-rays, but via the phenomenon of planar channeling they may act as waveguide for relativistic charged particles beam as well, outperforming some of the traditional technologies currently employed. A physical description of the phenomenon and the resulting potential for applications in a particle accelerator is reported. The elastic properties of the anisotropic crystal lattice medium are discussed, introducing different types of curvature which can enable a wide array of bending schemes optimized for each different case features. The technological development of machining strategy and bending solutions useful for the fabrication of crystals suitable in high energy particle manipulations are described. As well as the high precision characterization processes developed in order to satisfy the strict requirements for installation in an accelerator. Finally, the characterization of channeling phenomenon in bent crystal is described, pointing out several experimental setups suitable to comply each specific case constrains.

Membrane Remodeling Due to a Mixture of Multiple Types of Curvature Proteins.

We present an extension of the Monte Carlo based mesoscopic membrane model, where the membrane is represented as a dynamically triangulated surface and the proteins are modeled as anisotropic inclusions formulated as in-plane nematic field variables adhering to the deformable elastic sheet. In the extended model, we have augmented the Hamiltonian to study membrane deformation due to a mixture of multiple types of curvature generating proteins. This feature opens the door for understanding how multiple kinds of curvature-generating proteins may be working in a coordinated manner to induce desired membrane morphologies. For example, among other things, we study membrane deformations and tubulation due to a mixture of positive and negative curvature proteins as mimics of various proteins from BAR domain family. We also study the effect of membrane anisotropy that manifests as differential binding affinity and organization of curvature proteins, leading to insights into the tightly regulated cargo sorting and transport processes. Our simulation results show different morphology of deformed vesicles that depend on membrane tension, the curvatures and number of the participating proteins as well as on protein-protein and membrane-protein interactions.

Geometric sampling of networks

Abstract Motivated by the methods and results of manifold sampling based on Ricci curvature, we propose a similar approach for networks. To this end, we make an appeal to three types of discrete curvature, namely the graph Forman-, full Forman- and Haantjes–Ricci curvatures for edge-based and node-based sampling. The relation between the Ricci curvature of the original manifold and that of a Ricci curvature driven-discretization is studied, and we show that there is a strong connection between the Forman–Ricci curvatures of the resulting network and the Ricci curvature of the given smooth manifold. We also present the results of experiments on real-life networks, as well as for square grids arising in image processing. Moreover, we consider fitting Ricci flows, and we employ them for the detection of networks’ backbone.

Attribute-assisted interpretation of deltaic channel system using enhanced 3D seismic data, offshore Nova Scotia

Deltaic channels are good exploration targets and form potential hydrocarbon reservoirs. Generally, distributary sand-filled deltaic channels have high porosity and high permeability sandstones hence can form good quality reservoirs. We delineate deltaic channels within Cree Sand member of the Logan Canyon formation in the Penobscot field, offshore Nova Scotia, by devising a workflow that includes seismic data enhancement and attribute studies integrating coherence attributes, amplitude curvature and spectral decomposition attributes. An exhaustive seismic data conditioning improves considerably the signal-to-noise ratio in the conditioned seismic data (-4 dB at dominant frequency) compared to the input seismic (−22 dB at dominant frequency). We perform an integrated seismic attribute study which helps in effectively mapping the deltaic channel systems at different stratigraphic levels of the Cree Sand interval. We carry out a novel attribute analysis by comparing two types of volumetric curvature attributes namely, structural and amplitude curvatures. The structural curvature although depicting the fault patterns clearly, does not delineate the channels due to the absence of any flexure across the channel. Interestingly, the amplitude curvature attribute delineates different channel systems because of the amplitude variation across the channel edges. We identify narrower and thinner channels at the deeper stratigraphic level, while wider and thicker channels appear at the shallower level. Channel width varies from 870 m to 420 m and thickness from 110 m to 52 m from shallow to deeper level. Based on the integrated seismic attributes analysis, we identify varying channel width and thickness at different stratigraphic levels, that correlates to varying sea level.

Numerical Analysis of Single-Particle Motion Using CFD-DEM in Varying-Curvature Elbows

Centrifugal pumps are the critical components in deep-sea mining. In order to investigate the particle motion in the curved channel of the impeller, three different types of curvature conform to blade profile to simplify the impeller design of pumps. A numerical study is conducted to investigate the flow field in a varying-curvature channel for solid-liquid two-phase flow. The flow of particles within the varying curvature channel is studied by combining the discrete element method (DEM) with computational fluid dynamics (CFD) and a comparison with Particle Image Velocimetry (PIV) test results. The results show that a polyhedral mesh with a small mesh number yields very accurate results, which makes it very suitable for CFD-DEM. Based on this method, the movement of a single particle is compared and analyzed, and the particle-motion law is obtained. The effects of the curvature ratio Cr and area ratio Ar on the motion law for a single particle are studied, and the simulation results are analyzed statistically. The results show that the effect of Cr on both the particle slip velocity and the turbulent kinetic energy only changes its strength, while the distribution law does not change significantly. Compared with the curvature ratio Cr, the area ratio Ar has a greater impact on the particles, and its distribution law becomes clearly different. As the area ratio Ar increases, the arc radius and length of the corresponding particle trajectory decrease.

Curve approximation by G1 arc splines with a limited number of types of curvature and length

A method for approximating planar curves by G1 continuous arc splines with a limited number of types of curvatures and lengths, named k-arc splines, is proposed. A k-arc spline is a particular arc spline, and it has only k types of arcs less than the total number of segments. Due to this property, k-arc splines require discrete variables that relate segments and k types of arcs for representation. Therefore k-arc spline approximation problems must deal with discrete variables in contrast to general arc spline approximation problems. The authors present a method to appropriately estimate these variables from curvature values of a target curve. The proposed method enables a formulation of the approximation problem as a continuous optimization problem that conventional optimization algorithms can solve efficiently. The estimation method also provides a suitable initial solution for the algorithms. Some examples to show the broad applicability of the proposed algorithm are shown.

Surface model of the human red blood cell simulating changes in membrane curvature under strain

We present mathematical simulations of shapes of red blood cells (RBCs) and their cytoskeleton when they are subjected to linear strain. The cell surface is described by a previously reported quartic equation in three dimensional (3D) Cartesian space. Using recently available functions in Mathematica to triangularize the surfaces we computed four types of curvature of the membrane. We also mapped changes in mesh-triangle area and curvatures as the RBCs were distorted. The highly deformable red blood cell (erythrocyte; RBC) responds to mechanically imposed shape changes with enhanced glycolytic flux and cation transport. Such morphological changes are produced experimentally by suspending the cells in a gelatin gel, which is then elongated or compressed in a custom apparatus inside an NMR spectrometer. A key observation is the extent to which the maximum and minimum Principal Curvatures are localized symmetrically in patches at the poles or equators and distributed in rings around the main axis of the strained RBC. Changes on the nanometre to micro-meter scale of curvature, suggest activation of only a subset of the intrinsic mechanosensitive cation channels, Piezo1, during experiments carried out with controlled distortions, which persist for many hours. This finding is relevant to a proposal for non-uniform distribution of Piezo1 molecules around the RBC membrane. However, if the curvature that gates Piezo1 is at a very fine length scale, then membrane tension will determine local curvature; so, curvatures as computed here (in contrast to much finer surface irregularities) may not influence Piezo1 activity. Nevertheless, our analytical methods can be extended address these new mechanistic proposals. The geometrical reorganization of the simulated cytoskeleton informs ideas about the mechanism of concerted metabolic and cation-flux responses of the RBC to mechanically imposed shape changes.

How Cerebral Vessel Tortuosity Affects Development and Recurrence of Aneurysm: Outer Curvature versus Bifurcation Type.

Background and PurposePrevious studies have assessed the relationship between cerebral vessel tortuosity and intracranial aneurysm (IA) based on two-dimensional brain image analysis. We evaluated the relationship between cerebral vessel tortuosity and IA according to the hemodynamic location using three-dimensional (3D) analysis and studied the effect of tortuosity on the recurrence of treated IA. MethodsWe collected clinical and imaging data from patients with IA and disease-free controls. IAs were categorized into outer curvature and bifurcation types. Computerized analysis of the images provided information on the length of the arterial segment and tortuosity of the cerebral arteries in 3D space. ResultsData from 95 patients with IA and 95 controls were analyzed. Regarding parent vessel tortuosity index (TI; P<0.01), average TI (P<0.01), basilar artery (BA; P=0.02), left posterior cerebral artery (P=0.03), both vertebral arteries (VAs; P<0.01), and right internal carotid artery (P<0.01), there was a significant difference only in the outer curvature type compared with the control group. The outer curvature type was analyzed, and the occurrence of an IA was associated with increased TI of the parent vessel, average, BA, right middle cerebral artery, and both VAs in the logistic regression analysis. However, in all aneurysm cases, recanalization of the treated aneurysm was inversely associated with increased TI of the parent vessels. ConclusionsTIs of intracranial arteries are associated with the occurrence of IA, especially in the outer curvature type. IAs with a high TI in the parent vessel showed good outcomes with endovascular treatment.

Effective field equations and scale-dependent couplings in gravity

A new set of field equations for a space-time dependent Newton's constant $G(x)$ and cosmological constant $\Lambda(x)$ in the presence of matter is presented. We prove that it represents the most general mathematically consistent, physically plausible, set of evolution equations assuming at most second derivatives in the dynamical variables. In the new Einstein's equations, only $\Lambda$-kinetic terms arise, while in the modified conservation equation, derivative terms of $G$ also appear. As an application, this formalism is applied in the context of the Asymptotic Safety scenario to the early universe, assuming a perfect fluid with a radiation equation of state. Cosmological solutions are obtained for all types of spatial curvature, displaying a variety of interesting cosmic evolutions. As an indication of such behaviours, bouncing solutions, recollapsing solutions or non-singular expanding solutions with a transient acceleration era are discussed in details.