Axial Translation Research Articles

Design and Simulation of a Five Degrees of Freedom Active Control Magnetic Levitated Motor

A novel magnetically levitated motor which has the ability to control five degrees of freedom was proposed. The proposed magnetic levitated motor uses a radial bearing-less motor to control both radial translation motion and rotation, and an axial magnetic bearing to control both axial translation and tilting motion. Moreover, stators were installed on the inner side of the rotor, such that the flux path of the axial magnetic bearing and radial bearing-less motor are partially-shared. Therefore, the proposed magnetic levitated motor is small, while achieving five degrees of freedom active control. The prototype device was designed using FEM. According to this analysis, the device had sufficient magnetic force to control the rotor within a designed airgap of ± 0.6 mm. Moreover, simulated dynamic characteristics showed good response performance of the proposed maglev system.

Optical encryption using multiple intensity samplings in the axial domain

Image encryption with optical means has attracted attention due to its inherent multidimensionality and degrees of freedom, including phase, amplitude, polarization, and wavelength. In this paper, we propose an optical encoding system based on multiple intensity samplings of the complex-amplitude wavefront with axial translation of the image sensor. The optical encoding system is developed based on a single optical path, where multiple diffraction patterns, i.e., ciphertexts, are sequentially recorded through the axial translation of a CCD camera. During image decryption, an iterative phase retrieval algorithm is proposed for extracting the plaintext from ciphertexts. The results demonstrate that the proposed phase retrieval algorithm possesses a rapid convergence rate during image decryption, and high security can be achieved in the proposed optical cryptosystem. In addition, other advantages of the proposed method, such as high robustness against ciphertext contaminations, are also analyzed.

Estimation of Joint Incongruence in Dysplastic Canine Elbows Before and After Dynamic Proximal Ulnar Osteotomy

To characterize joint incongruence in dysplastic canine elbows before and after dynamic proximal ulnar osteotomy (DPUO). Clinical, prospective study. Dogs (n = 10; 12 elbows) with ≥ 2 mm radioulnar incongruence (RUI), FCP, and/or OCD. Computed tomography in a nonload bearing position was used to generate in silico 3D models of the elbow joint before DPUO, and this was repeated after DPUO union (median 3 months postoperatively). On these models, RUI, humeroradial and humeroulnar subchondral joint space width (SJSW) as well as alignment of the proximal ulnar segment were investigated. RUI at the medial coronoid process (MCP) decreased (P = .001), while it increased at the lateral coronoid process (P = .0005), and remained unchanged at the level of the trochlear ridge (P = .25). SJSW at the MCP increased (P = .001), changing from focal joint space collapse preoperatively to a more homogeneous pattern of moderate SJSW at follow-up. The proximal ulnar segment rotated in all 3 planes with caudal tipping at the level of the osteotomy and varus deformity, while no axial translation could be noted. DPUO results in reduction of RUI and amelioration of focal contact area at the MCP. This effect is the result of a complex three-dimensional rotation of the proximal ulnar segment, rather than axial shift.

Measuring incidence angle for through-the-objective total internal reflection fluorescence microscopy

Total internal reflection fluorescence (TIRF) microscopy has the exciting laser beam incident beyond critical angle from the glass side of a glass/aqueous interface formed by the coverslip and aqueous sample. The aqueous side evanescent field decays exponentially with distance from the interface with penetration depth depending on incidence angle. Through-the-objective TIRF has the exciting laser focused at the back focal plane (BFP) creating a refracted parallel beam approaching the interface in the small gap between objective and coverslip, making incidence angle challenging to measure. Objective axial scanning does not affect incidence angle but translates beam and interface intersection detected by the fluorescence center of mass from fluorescent spheres attached to the aqueous side of the interface. Center of mass translation divided by the axial translation is the tangent of the incidence angle that is sampled repeatedly over objective trajectory to obtain a best estimate. Incidence angle is measured for progressively larger radial positions of the focused beam on the BFP. A through-the-objective TIRF microscope, utilizing a micrometer and relay lenses to position the focused beam at the BFP, is calibrated for incidence angle. Calibration depends on microscope characteristics and TIRF objective and is applicable to any interface or sample.

Optimization of two-glass monocentric lenses for compact panoramic imagers: general aberration analysis and specific designs

Monocentric lenses have recently changed from primarily a historic curiosity to a potential solution for panoramic high-resolution imagers, where the spherical image surface is directly detected by curved image sensors or optically transferred onto multiple conventional flat focal planes. We compare imaging and waveguide-based transfer of the spherical image surface formed by the monocentric lens onto planar image sensors, showing that both approaches can make the system input aperture and resolution substantially independent of the input angle. We present aberration analysis that demonstrates that wide-field monocentric lenses can be focused by purely axial translation and describe a systematic design process to identify the best designs for two-glass symmetric monocentric lenses. Finally, we use this approach to design an F/1.7, 12 mm focal length imager with an up to 160° field of view and show that it compares favorably in size and performance to conventional wide-angle imagers.

Finite Displacement Screw Operators With Embedded Chasles’ Motion

Rigid body displacement can be presented with Chasles’ motion by rotating about an axis and translating along the axis. This motion can be implemented by a finite displacement screw operator in the form of either a 3 × 3 dual-number matrix or a 6 × 6 matrix that is executed with rotation and translation as an adjoint action of the Lie group. This paper investigates characteristics of this finite displacement screw matrix and decomposes the secondary part that is the off diagonal part of the matrix into the part of an equivalent translation due to the effect of off-setting the rotation axis and the part of an axial translation. The paper hence presents for the first time the axial translation matrix and reveals its property, leading to discovery of new results and new formulae. The analysis further reveals two new traces of the matrix and presents the relationship between the finite displacement screw matrix and the instantaneous screw, leading to the understanding of Chasles’ motion embedded in a rigid body displacement. An algebraic and geometrical interpretation of the finite displacementscrew matrix is thus given, presenting an intrinsic property of the matrix in relation to the finite displacement screw. The paper ends with a case study to verify the theory and illustrate the principle.

Angulated locking plate in periprosthetic proximal femur fractures: biomechanical testing of a new prototype plate

To improve proximal plate fixation of periprosthetic femur fractures, a prototype locking plate with proximal posterior angulated screw positioning was developed and biomechanically tested. Twelve fresh frozen, bone mineral density matched human femora, instrumented with cemented hip endoprosthesis were osteotomized simulating a Vancouver B1 fracture. Specimens were fixed proximally with monocortical (LCP) or angulated bicortical (A-LCP) head-locking screws. Biomechanical testing comprised quasi-static axial bending and torsion and cyclic axial loading until catastrophic failure with motion tracking. Axial bending and torsional stiffness of the A-LCP construct were (1,633 N/mm ± 548 standard deviation (SD); 0.75 Nm/deg ± 0.23 SD) at the beginning and (1,368 N/mm ± 650 SD; 0.67 Nm/deg ± 0.25 SD) after 10,000 cycles compared to the LCP construct (1,402 N/mm ± 272 SD; 0.54 Nm/deg ± 0.19 SD) at the beginning and (1,029 N/mm ± 387 SD; 0.45 Nm/deg ± 0.15) after 10,000 cycles. Relative movements for medial bending and axial translation differed significantly between the constructs after 5,000 cycles (A-LCP 2.09° ± 0.57 SD; LCP 5.02° ± 4.04 SD; p = 0.02; A-LCP 1.25 mm ± 0.33 SD; LCP 2.81 mm ± 2.32 SD; p = 0.02) and after 15,000 cycles (A-LCP 2.96° ± 0.70; LCP 6.52° ± 2.31; p = 0.01; A-LCP 1.68 mm ± 0.32; LCP 3.14 mm ± 0.68; p = 0.01). Cycles to failure (criterion 2 mm axial translation) differed significantly between A-LCP (15,500 ± 2,828 SD) and LCP construct (5,417 ± 7,236 SD), p = 0.03. Bicortical angulated screw positioning showed less interfragmentary osteotomy movement and improves osteosynthesis in periprosthetic fractures.

The locking attachment plate for proximal fixation of periprosthetic femur fractures—a biomechanical comparison of two techniques

Mechanical properties of a locking attachment plate construct (LAP-LCP), allowing bicortical screw placement laterally to the prosthesis stem, are compared to a cerclage-LCP construct. Eight right synthetic femora with implanted uncemented hip endoprosthesis were cut distally and fixed with LCP, monocortical locking screws and either LAP (n = 4) or cerclage (n = 4). Cyclic testing was performed with monotonically increasing sinusoidal load until failure. Relative movements at the plate-femur interface were registered by motion tracking. Statistical differences were detected by unpaired t-test and general linear model repeated measures. Stiffness of the LAP-LCP was significantly higher at the beginning (875.4 N/mm ± 29.8) and after 5000 cycles (1213.0 N/mm ± 101.1) compared to the cerclage-LCP (644.96 N/mm ± 50.1 and 851.9 N/mm ± 81.9), with p = 0.013. Relative movements for AP-bending (B) and axial translation (T) of the LAP-LCP at the beginning (0.07° ± 0.02, 0.20 mm ± 0.08), after 500 cycles (0.16° ± 0.10, 0.26 mm ± 0.07) and after 5000 cycles (0.26° ± 0.11, 0.31 mm ± 0.07) differed significantly from the cerclage-LCP (beg.: 0.26° ± 0.04, 0.28 mm ± 0.05; 500 cyc: 0.47° ± 0.03, 0.53 mm ± 0.07; 5000 cyc.: 0.63° ± 0.18, 0.79 mm ± 0.13), with B: p = 0.02, T: p = 0.04. Relative movements for medial bending were not significantly different between the two constructs. Cycles to failure (criterion 1 mm axial translation) differed significantly between LAP-LCP (19,519 ± 1,758) and cerclage-LCP (11,265 ± 2,472), with p = 0.035. Biomechanically, the LAP-LCP construct improves proximal fixation of periprosthetic fractures compared to the cerclage-LCP construct.

Comparison of 4 Airway Devices on Cervical Spine Alignment in a Cadaver Model With Global Ligamentous Instability at C5–C6

Human cadaveric study using various intubation devices in a cervical spine instability model. We sought to evaluate various intubation techniques and determine which device results in the least cervical motion in the setting of a global ligamentous instability model. Many patients presenting with a cervical spine injury have other injuries that may require rapid airway management with endotracheal intubation. Secondary neurologic injuries may occur in these patients because of further displacement at the level of injury, vascular insult, or systemic decrease in oxygen delivery. The most appropriate technique for achieving endotracheal intubation in the patient with a cervical spine injury remains controversial. A global ligamentous instability at the C5-C6 vertebral level was created in lightly embalmed cadavers. An electromagnetic motion analysis device (Liberty; Polhemus, Colchester, VT) was used to assess the amount of angular and linear translation in 3 planes during intubation trials with each of 4 devices (Airtraq laryngoscope, lighted stylet, intubating LMA, and Macintosh laryngoscope). The angular motions measured were flexion-extension, axial rotation, and lateral bending. Linear translation was measured in the medial-lateral (ML), axial, and anteroposterior planes. Intubation was performed by either an emergency medical technician or by a board-certified attending anesthesiologist. Both time to intubate as well as failure to intubate (after 3 attempts) were recorded. There was no significant difference shown with regards to time to successfully intubate using the various devices. It was shown that the highest failure-to-intubate rate occurred with use of the intubating LMA (ILMA) (23%) versus 0% for the others. In flexion/extension, we were able to demonstrate that the Lightwand (P = 0.005) and Airtraq (P = 0.019) resulted in significantly less angular motion than the Macintosh blade. In anterior/posterior translation, the Lightwand (P = 0.005), Airtraq (P = 0.024), and ILMA (P = 0.021) all caused significantly less linear motion than the Macintosh blade. In axial rotation, the Lightwand (P = 0.017) and Airtraq (P = 0.022) resulted in significantly less angular motion than the Macintosh blade. In axial translation (P = 0.037) and lateral bending (P = 0.003), the Lightwand caused significantly less motion than the Macintosh blade. In a cadaver model of C5-C6 instability, the greatest amount of motion was caused by the most commonly used intubation device, the Macintosh blade. Intubation with the Lightwand resulted in significantly less motion in all tested parameters (other than ML translation) as compared with the Macintosh blade. It should also be noted that the Airtraq caused less motion than the Macintoshblade in 3 of the 6 tested planes. There were no significant differences in failure rate or the amount of time it took to successfully intubate in comparing these techniques. We therefore recommend the use of the Lightwand, followed by the Airtraq, in the setting of a presumed unstable cervical spine injury over the Macintosh laryngoscope.

The KneeKG system: a review of the literature

Accurately quantifying knee joint motion is not simple. Skin movement over the medial and lateral femoral condyles is the greatest obstacle to obtaining accurate movement data non-invasively. The KneeKG™ system was developed with the objective of providing high reliability movement analysis. The goal of this manuscript is to review the technical details, clinical evidence, and potential applications of this system for evaluation of rotational knee laxity. A comprehensive review of the MEDLINE database was carried out to identify all clinical and biomechanical studies related to KneeKG™ system. The KneeKG™ system non-invasively quantifies knee abduction/adduction, axial rotation, and relative translation of the tibia and femur. The accuracy and reproducibility of the system have been assessed. The average accuracy of the acquisition is 0.4° for abduction/adduction, 2.3° for axial rotation, 2.4mm for anteroposterior translation, and 1.1mm for axial translation. This clinical tool enables an accurate and objective assessment of the tri-planar function of the knee joint. The measured biomechanical parameters are sensitive to changes in gait due to knee osteoarthritis and ACL deficiency. The KneeKG™ system provides reliable movement analysis. This system has the potential to improve understanding the biomechanical consequences of trauma or degenerative changes of the knee as well as more accurately quantify rotational laxity as detected by a positive pivot-shift test.

Motion in the unstable thoracolumbar spine when spine boarding a prone patient

IntroductionPrevious research has found that the log roll (LR) technique produces significant motion in the spinal column while transferring a supine patient onto a spine board. The purpose of this project was to determine whether log rolling a patient with an unstable spine from prone to supine with a pulling motion provides better thoracolumbar immobilization compared to log rolling with a push technique.MethodsA global instability was surgically created at the L1 level in five cadavers. Two spine-boarding protocols were tested (LR Push and LR Pull). Both techniques entailed performing a 180° LR rotation of the prone patient from the ground to the supine position on the spine board. An electromagnetic tracking device registered motion between the T12 and L2 vertebral segments. Six motion parameters were tracked. Repeated-measures statistical analysis was performed to evaluate angular and translational motion.ResultsLess motion was produced during the LR Push compared to the LR Pull for all six motion parameters. The difference was statistically significant for three of the six parameters (flexion–extension, axial translation, and anterior–posterior (A–P) translation).ConclusionsBoth the LR Push and LR Pull generated significant motion in the thoracolumbar spine during the prone to supine LR. The LR Push technique produced statistically less motion than the LR Pull, and should be considered when a prone patient with a suspected thoracolumbar injury needs to be transferred to a long spine board. More research is needed to identify techniques to further reduce the motion in the unstable spine during prone to supine LR.

Intraocular lens implantation position sensitivity as a function of refractive error

To quantify the change in ocular aberrations due to intraocular lens (IOL) implantation position errors for pseudo-phakic eyes with different refractive errors. The theoretical part of this work was based on ray-tracing in emmetropic and myopic eye models. The possible misalignments i.e. the decentration, tilt and axial translation, of the IOLs were statistically combined together and analysed using Monte-Carlo simulations. Spherical IOLs with a 3 and 5 mm pupil and an aspheric IOL with a 5 mm pupil were analysed as a function of refractive error. In the experimental part of the work, we built an IOL optical test bench including a model eye. The white light discrete point spread functions of misaligned IOLs were recorded by a CCD and we compared the change of the spread function as a result of misalignments for two spherical IOLs with different optical powers. The Monte-Carlo simulations showed that the average root-mean-square spot size at the retinal plane decreased with increasing myopic refractive error, i.e. lower power IOL. The experiments showed that a lower optical power spherical IOL had a less distributed point spread function than a higher optical power IOL, which supported the results of the simulation. Regarding IOLs designed for myopic patients, low power IOLs (for high myopes) were shown to be less sensitive to the misalignment than high power ones. Aspheric IOLs were more sensitive to position errors than spherical IOLs under the same conditions.

Cold matter trapping via slowly rotating helical potential

We consider the cold bosonic ensemble trapped by a helical interference pattern in the optical loop scheme. This rotating helical potential is produced by the two slightly detuned counter-propagating Laguerre–Gaussian laser beams with counter-directed orbital angular momenta ±ℓℏ. The detuning δω may occur due to rotational Doppler effect. The superfluid hydrodynamics is analyzed for the large number of trapped atoms in Thomas–Fermi approximation. For the highly elongated trap the Gross–Pitaevskii equation is solved in a slowly varying envelope approximation. The speed of axial translation and angular momenta of interacting atomic cloud are evaluated. In the T→0 limit the angular momentum of the helical cloud is expected to be zero while toroidal trapping geometry leads to 2ℓℏ angular momentum per trapped atom.

Evidence for short-range helical order in the 30-nm chromatin fibers of erythrocyte nuclei

Chromatin folding in eukaryotes fits the genome into the limited volume of the cell nucleus. Formation of higher-order chromatin structures attenuates DNA accessibility, thus contributing to the control of essential genome functions such as transcription, DNA replication, and repair. The 30-nm fiber is thought to be the first hierarchical level of chromatin folding, but the nucleosome arrangement in the compact 30-nm fiber was previously unknown. We used cryoelectron tomography of vitreous sections to determine the structure of the compact, native 30-nm fiber of avian erythrocyte nuclei. The predominant geometry of the 30-nm fiber revealed by subtomogram averaging is a left-handed two-start helix with approximately 6.5 nucleosomes per 11 nm, in which the nucleosomes are juxtaposed face-to-face but are shifted off their superhelical axes with an axial translation of approximately 3.4 nm and an azimuthal rotation of approximately 54°. The nucleosomes produce a checkerboard pattern when observed in the direction perpendicular to the fiber axis but are not interdigitated. The nucleosome packing within the fibers shows larger center-to-center internucleosomal distances than previously anticipated, thus excluding the possibility of core-to-core interactions, explaining how transcription and regulation factors can access nucleosomes.

Haptic Simulator for Prostate Brachytherapy with Simulated Needle and Probe Interaction

This paper presents a haptic simulator for prostate brachytherapy. Both needle insertion and the manipulation of the transrectal ultrasound (TRUS) probe are controlled via haptic devices. Tissue interaction forces that are computed by a deformable tissue model based on the finite element method (FEM) are rendered to the user by these devices. The needle insertion simulation employs 3D models of needle flexibility and asymmetric tip bevel. The needle-tissue simulation allows a trainee to practice needle insertion and targeting. The TRUS-tissue interaction simulation allows a trainee to practice the 3D intraoperative TRUS placement for registration with the preoperative volume study and to practice TRUS axial translation and rotation for imaging needles during insertions. Approaches to computational acceleration for realtime haptic performance are presented. Trade-offs between accuracy and speed are discussed. A graphics-card implementation of the numerically intensive mesh-adaptation operation is also presented. The simulator can be used for training, rehearsal, and treatment planning.

Dynamic response of clamped axially moving beams: Integral transform solution

The generalized integral transform technique (GITT) is employed to obtain a hybrid analytical–numerical solution for dynamic response of clamped axially moving beams. The use of the GITT approach in the analysis of the transverse vibration equation leads to a coupled system of second order differential equations in the dimensionless temporal variable. The resulting transformed ODE system is then solved numerically with automatic global accuracy control by using the subroutine DIVPAG from IMSL Library. Excellent convergence behavior is shown by comparing the vibration displacement of different points along the beam length. Numerical results are presented for different values of axial translation velocity and flexural stiffness. A set of reference results for the transverse vibration displacement of axially moving beam is provided for future co-validation purposes.

Experimental Study of New High-Frequency Valve

A double degree of freedom valve was designed. It has the functions of the radial direction rotary motion and the axial translation motion. In the electro-hydraulic vibrator, 2D valves are used to control hydraulic cylinder to achieve high-frequency vibration. The vibration frequency and amplitude are controlled by the speed and axial displacement in the spool valve core respectively. The vibration-exciting force signals and the displacement signals are obtained by adapting card under Delphi development. The real excited waveforms are analyzed, compared and studied.

Numerical reconstruction in in-line digital holography by translation of CCD position and gradient operator method

We propose an approach based on axial translation of a charge-coupled device (CCD) and gradient operator method for numerical reconstruction in in-line digital holography. The object wave in the hologram (or CCD) plane is determined using one position translation of CCD, and a phase-shifting device can be fully avoided. Gradient operator method is further applied to detect the focal plane of an object, and the object wave is reconstructed by an angular spectrum algorithm with the detected focal distance. The feasibility and effectiveness of the proposed method are demonstrated by numerical simulations.

Effect of Short-Duration Low-Magnitude Cyclic Loading Versus Immobilization on Tendon-Bone Healing After ACL Reconstruction in a Rat Model

Successful anterior cruciate ligament reconstruction with use of soft-tissue grafts requires healing between tendon and bone. Little is known about the effect of mechanical load on the cellular and molecular cascade of tendon-to-bone healing. Understanding these mechanical influences has critical implications for postoperative rehabilitation following anterior cruciate ligament reconstruction. The purpose of this study was to test the hypothesis that, compared with perioperative immobilization, short-duration low-magnitude cyclic axial loading would result in impaired tendon-to-bone healing after anterior cruciate ligament reconstruction in a rat model. Fifty-two male Sprague-Dawley rats underwent anterior cruciate ligament reconstruction with use of a flexor digitorum longus autograft. The patellar tendon, capsule, and ligamentous structures were circumferentially released, and an external fixator parallel to the anterior cruciate ligament graft was placed across the knee. Mechanical loading, consisting of cyclic displacement of the femur and tibia constrained to axial translation parallel to the graft, was applied daily. The rats were randomly assigned to immobilization or daily loading, for fourteen or twenty-eight days. Biomechanical, micro-computed tomographic, and histomorphometric analysis was performed on the bone-tendon-bone complexes. The load measured across the knees during cyclic displacement increased over time (p < 0.05). Load-to-failure testing of the isolated femur-anterior cruciate ligament graft-tibia specimens revealed no significant differences between groups at two or four weeks. By two weeks postoperatively, a greater number of ED1+ inflammatory macrophages (phagocytic cells involved in the initial injury response) were seen at the tendon-bone interface after loading in the cyclically loaded group than in the immobilized group (p = 0.01). Compared with the baseline values, the number of trabeculae was significantly lower after loading for four weeks (p = 0.02). Short-duration low-magnitude cyclic axial loading of the anterior cruciate ligament graft in the postoperative period is not detrimental to the strength of the healing tendon-bone interface but appears to be associated with greater inflammation and less bone formation in the tunnel in this rat model.

Sustained smooth dynamics in short-sleeved nanobearings based on double-walled carbonnanotubes

We carry out a molecular dynamics study of nanobearings based on double-walled carbonnanotubes with a short rotating outer tube. A (4, 4)/(9, 9) bearing configuration showspeculiar stabilization of rotational motion at certain values of angular velocities. Theobserved trend is found at those values of initial angular velocities (in the current context,0.8–1.5 rad ps − 1) which denote a transitional regime between nearly frictionless operation at low initialangular speeds and decaying performance at high initial angular velocities. With the use ofdetailed ‘principal components analysis’, we find that the energy dissipation occurs mainlydue to the excitation of wavy modes in the inner tube of the bearing. It is also proposedthat wavy deformation is facilitated by the actuation of axial translation of the outer tube,which acts as an energy channelling mode. Hence, we find that the absence of dissipativewavy modes results in sustained smooth rotational dynamics of the nanobearing at lowtemperature.