Oblique Entry Research Articles

Humeral Head Reconstruction of Reverse Hill-Sachs Lesions With Osteochondral Allograft

Background: True confirmed posterior shoulder dislocations are relatively uncommon injuries, with an estimated incidence of 1.1 per 100,000 individuals and are initially missed in up to 50% to 80% of cases. There are several treatment options for this injury presentation. In this case, we will focus on reconstruction with osteochondral allograft. Indications: If the cartilage cannot be fixed due to comminution or the cartilage is not viable due to chronicity or impact, osteochondral allograft might be a treatment option. This technique is typically considered for defects involving greater than 35% to 40% of the humeral head. Technique Description: The anterior defect on the humeral head was exposed on the cadaver specimen. Circular bone plugs were obtained from a distal femur specimen for grafting. Graft sites were prepared with a 15 reamer with an orthogonal approach to avoid oblique entry for a stacked bone plug configuration. Bone plug grafts were placed in the defect via press-fit fixation. The subscapularis is repaired to the lesser tubercle following the reconstruction. Results: Various studies reported improvement in pain, shoulder range of motion, and patient-reported outcome scores. A small percentage of patients developed allograft necrosis. Patients who received autografts had lower rates of osteoarthritis than patients who received allograft. Rehab protocol can last up to 12 months and begins with restricted range of motions and slowly advancing to isometric movements and gradually increasing range of motion and strengthening. Discussion/Conclusion: Outcomes described in previous studies are limited due to the low incidence of these injuries and small sample size. Missing the initial posterior dislocation as this is often correlated with inferior outcomes when treated in chronic setting. There is a risk of damage to humeral articular cartilage during osteochondral tissue harvesting so care must be taken during tissue harvest. Older, lower-demand patients have been reported to do well with nonoperative treatment, even in the case of a chronic dislocation, so careful discussion with the patient is needed to not perform surgery in a reasonably functioning non-painful shoulder. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Experimental study on load characteristics of vehicle during high-speed water entry

During the process of high-speed water entry, the vehicle will bear large loads. Obtaining and analysing the time-frequency characteristics of loads is of great engineering significance for the protection of shell and equipment. The high-speed camera is used to capture the evolution of cavity and the accelerometer is used to collect the acceleration of model during water entry. The time-frequency characteristics of acceleration are obtained based on the short-time Fourier transform and discrete wavelet transform. The results indicate that the cavity exhibits an asymmetric shape and shrinks near free surface during the oblique high-speed water entry. When the cavity undergoes closure and collapse, the collapsing order of the upper and lower parts is opposite. Through the short time Fourier transform, it was found that the loads contain components of different frequency at different periods. When the model collides with free surface, the frequency contained in acceleration are more complex, reflecting the complexity of mechanical environment. The discrete wavelet transform is used to extract the components with more time-resolution and obtain the relative energy of each component. It is found that the relative energy of low-frequency components increases with the increase of water entry speed.

Slanted Translation[s]: An Interview with Artist Rosanna Bruno

In this interview-essay, artist Rosanna Bruno talks with the author about her illustrations of The Trojan Women, a comic-book made in collaboration with Anne Carson. Bruno’s illustrations offer the reader an oblique entry into a devastated Troy: they are translation “at a slant.” The artist speaks on going against what is visually expected or plausible, in her use of surprising imagery to convey and counterpoint suffering, and touches upon the use of humor to bring the tragedy into sharp focus. Bruno explains how the comic-book format can communicate radical ideas in the interdependence of word and image. She talks through creating the feeling of live theater and the emotional tenor brought about by an almost entirely non-human cast: dogs, cows, a huge wave, a turnip-like rootling, a pair of dungarees. The illustrator elucidates the collaborative process between herself and Carson, revealing the various iterations of characters before they settled on their final forms, and the materials and methodologies Bruno employed in its rendering.

Water impact of deformable spheres with vertical and oblique entries

At low Froude numbers, vertical and oblique impacts of deformable spheres into water are performed. The dependence levels of the hydrodynamics, cavity formations, and stress responses on the oblique angle are investigated. Based on theoretical and numerical analyses, the differences between the vertical and oblique impacts in sphere deformations and cavity formations are clarified. Elastic forces inside the sphere induce different models of the deformation behaviors during oblique water entry, and the sphere with a smaller oblique angle extends the formation time of the oblate deformation and nested cavity. Over a single deformation period, the vertical hydrodynamic forces do not continuously increase with the oblique angle, and they depend on the deformation behavior. Additionally, the evolution in the high-stress area at the bottom of the sphere caused by the oblique motion is similar to a solar eclipse. Over the first deformation period, the energy change in the sphere with different oblique angles can be predicted from the dimensionless ratio of the material shear modulus to the impact hydrodynamic pressure.

Numerical study on the water-entry characteristics of asynchronous parallel projectiles at an oblique impact angle

This study investigates the water-entry problems of asynchronous parallel projectiles with oblique entry speeds of 200 m/s for different water-entry intervals and two different water-entry sequences numerically. The experiment of the water-entry of the projectile with an oblique impact angle is conducted to verify the numerical method. The influences of the oblique asynchronous parallel water-entry on the evolutions of the cavitating flow and the movement characteristics under different working conditions are studied in detail. It can be found that for the minimum interval, the first launch projectile is not able to generate a complete cavity to encapsulate its body due to the intense compression of the cavity of the following launch projectile, and its movement is seriously affected and ultimately destabilized. Simultaneously, compared with the first launch projectile entering the water from the side close to the initial free surface, the cavity of the first launch projectile entering the water from the side away from the initial free surface is squeezed more, wetted earlier and destabilized faster. With the increase of the interval, the influence of the following launch projectile on the cavity evolution and movement stability of the first launch projectile weakens. Besides, for the following launch projectile, due to the continuous impact of the cavitating flow of the first launch projectile, the profile of the cavity of the following launch projectile presents asymmetry. For the minimum interval, the projectile deflects faster and towards the inner side of the projectile, while for the larger intervals, the projectile deflects to the outer side of the projectile and becomes unstable.

Morphometry and anatomical variations of the inferior oblique muscle as relevant to the strabismus surgeries

ABSTRACT Effective outcome of inferior oblique (IO) corrective surgeries demands a detailed knowledge of morphometry and variations of IO. Our aim was to study and morphometrically define the surgical anatomy of the IO muscle and its variations. Also to provide easily identifiable surgical coordinates to locate, the IO origin and the oculomotor nerve entry point into the IO. Dissection was performed on 16 cadaveric orbits. IO anatomy, variations, morphometry and relevant surgical distances were measured using digital caliper. IO with multiple bellies was found in five specimens. The IO mean length was 33.1 ± 3.3 mm, width at origin was 3.1 ± 0.6 mm, and width at insertion was 8.8 ± 1.5 mm. For easy localization of origin, its distance from the palpable landmarks, Zygomatico-maxillary suture and fronto-maxillary suture was measured. The mean distance between IO and the optic nerve was 10 mm. Distance of the nerve to inferior oblique entry point to the origin and insertion of the inferior oblique was measured. The nerve to IO was 28 mm long. The mean distance of the nerve entry point to IO origin was 15.5 ± 2.3 mm and distance to IO insertion was 15.2 ± 2.8 mm. A muscular bridge between the Inferior rectus (IR) & IO was found in one case, affecting ~¼ of the IO length; the distal end of the bridge was 5 mm from the IO insertion. Origin of the IO can be localized on the orbital surface of maxilla, 1–2 cm from the point where zygomatico-maxillary suture cuts the inferior orbital margin and 1–2 cm from the fronto-maxillary suture. In 19% of the orbits, the IO length was less than 30 mm, which may cause traction injury in muscle transposition procedures. The width at insertion is useful as most corrective surgeries are performed at the insertion site. The nerve to IO consistently entered at the center of medial border. The nerve entry point is important surgically as myectomy is performed between it and the insertion point. The safe distance available from the optic nerve was 7 mm. Detailed morphometry of IO may aid surgeons in better surgical planning and execution.

Classification of the collapse of a composite fairing during the oblique high-speed water entry

The crushing behaviors of the buffer devices for the projectile in the high-speed oblique water entry process were investigated numerically. The high-speed water entry tests of the aluminum alloy projectile with a sabot were conducted to study the cavity formation, also used to validate the numerical method. Detailed material parameters of three kinds of foams including expanded polystyrene foam (EPS), closed-cell aluminum foam, and rigid polyurethane foam (PU), and the composite material for the fairings were obtained from a series of statics and dynamics mechanics experiments. Twelve collapse modes of the thin-walled fairings were identified during the oblique water impact. The effects of the length of the fairing, foam type, and water entry angle on these failure modes, and the peak impact acceleration of the projectiles were revealed. The results showed that the load reduction efficiency (LRE) is dependent on both entry angle θ and dimensionless length LFA/DPJ. The critical load reduction water entry angle (CLRA) is linearly related to LFA/DPJ. Among the three kinds of foam materials, the closed-cell aluminum foam has the best load reduction performance (up to 72.82%) and the widest range of load reduction water entry angles. Meanwhile, the EPS foam makes the projectile withstand the largest impact overload (up to 11.43%).

Slamming force decomposition with gravity effect

In this paper, the original slamming force decomposition, where the total vertical slamming force is decomposed into speed and acceleration terms with coefficients depending on the penetration depth only, is further developed by including the gravity effect through an additional term that is only dependent on the penetration depth as well. The speed, acceleration and gravity related coefficients are extracted by Computational Fluid Dynamics (CFD) approach, where gravity can be readily included or excluded, using only small number of CFD computations for particular body motions. Then the components of the hydrodynamic force acting on the entering body can be evaluated using these coefficients and the force decomposition formula for any motion of the body avoiding direct CFD computations for each particular motion. CFD results show that the gravity significantly affects the slamming force for relatively small values of the entry speed. It is shown that the improved force decomposition provides an accurate approximation of the computed forces under various speed/acceleration combinations for arbitrary two-dimensional body shapes including vertical entry of symmetric/asymmetric bodies and oblique entry of symmetric bodies, except for penetrations with large deceleration when the body stops shortly after the flow separation.

On applicability of von Karman’s momentum theory in predicting the water entry load of V-shaped structures with varying initial velocity

The water landing of an amphibious aircraft is a complicated problem that can lead to uncomfortable riding situation and structural damage due to large vertical accelerations and the consequent dynamic responses. The problem herein is investigated by solving unsteady incompressible Reynolds-averaged Navier–Stokes equations with a standard k−ω turbulence closure model. The theoretical solutions established by the von Karman’s momentum theory are also employed. In order to validate the relationships between the initial vertical velocity and the peak value of vertical acceleration, free fall test cases of 2D symmetric wedge oblique entry and 3D cabin section vertical entry are presented first. The other parameters at which the maximum acceleration occurs, such as time, penetration depth, velocity, are also evaluated. Hence, the quantitative relations are investigated to water landing event for amphibious aircraft. Detailed results in terms of free surface shape and pressure distribution are provided to show the slamming effects. The results show that a linear dependence of the maximal acceleration from the square of initial vertical velocity can be derived for two-dimensional wedge, three-dimensional cabin section and seaplane with V-shaped hull. Moreover, the ratio between the corresponding velocity and the initial vertical velocity tends to a constant threshold value, 5/6, derived from the theoretical solution, when increasing the initial vertical velocity in all three cases.

Numerical study on the water-entry of asynchronous parallel projectiles at a high vertical entry speed

This study investigates the water-entry characteristics of asynchronous parallel projectiles with vertical entry speeds of 400 m/s for four different water-entry intervals numerically. Experimental studies on the cylinder and the projectile at a high oblique entry speed are carried out to validate the numerical method. The influences of the asynchronous parallel water-entry on flow filed characteristic, trajectory stability and drag reduction performance are conducted in detail. It can be found that the cavity of the first launch projectile is squeezed and the cavity of the following launch projectile expands. Finally, the cavities of two asynchronous parallel projectiles fuse and gradually elongate. For the minimum interval, a tail-slap happens on the first launch projectile, and the following launch projectile loses its trajectory stability totally. For the maximum interval, the following launch projectile is greatly affected by the strong interference of the cavity of the first launch projectile and shows a poor capability of stable. Besides, the water-entry of the first launch projectile decreases the maximum value of the impact load on the following launch projectile obviously. Due to the deformation of the cavity induced by the asynchronous parallel water-entry, the wetting phenomenon occurs on both projectiles, which results in the enlargement of the drag force coefficient and the instability of trajectory.

Cavity dynamics in the oblique water entry of a cylinder at constant velocity

Transient cavity dynamics in the oblique water entry of a cylinder at a constant velocity is investigated. The drag force exerted on the cylinder is measured by a force sensor, and the evolution of a cavity is recorded simultaneously by a high-speed camera. A simple theoretical model, based on the decomposition of gravity force, is proposed to describe the asymmetric cavity formed in the oblique water entry. Theoretically predicted cavity shapes compare favorably with the experimental and numerical results. Moreover, it is found that with a factor indicating the effect of entry angle, the pinch-off time and position in oblique and vertical water entry problems follow the same scaling law.

Intraocular pressure outcomes after 23-G vitreoretinal surgery with two different transconjunctival sutureless sclerotomy techniques: vertical versus tunnel entry.

Comparison of postoperative intraocular pressure (IOP) course and early complications in 23-gauge (23-G) pars plana vitrectomy (PPV) using vertical entry sclerotomy and scleral tunnel sclerotomy in uncomplicated rhegmatogenous retinal detachment (RRD). A prospective, randomized, comparative, interventional clinical trial of 103 23-G vitrectomy cases using two different transconjunctival sutureless sclerotomy techniques performed by a single vitreoretinal surgeon for uncomplicated RRD. Fifty-two eyes underwent PPV using a three-port 23-G single stage, vertical trocar entry without creating a scleral tunnel (Group 1), while in 51 eyes, a two-stage, oblique trocar entry with creation of a scleral tunnel was performed (Group 2). Sulfur hexafluoride (SF6) gas (20%) was used in all cases as a buffer. Intraocular pressure measurements and detailed biomicroscopic examination of the groups were recorded on the postoperative first day, first week, and first month. Visual acuity and fundoscopic examinations were recorded at one month. The effects of the two methods on postoperative intraocular pressure and early complications were compared. There was no significant difference between the two groups in terms of age and gender (p > 0.05). The mean postoperative intraocular pressure on the first day was 15.06 ± 3.71 for Group 1 and 16.14 ± 3.09mmHg for Group 2. The lowest recorded IOP was 6mmHg. Postoperative visual acuity did not differ between the two groups (p > 0.05). In addition, IOP values did not differ statistically between the two groups (p > 0.05). In both groups, the mean IOP values measured at different intervals did not differ statistically (p > 0.05). There was no significant difference in terms of postoperative IOP between vertical entry 23-G sclerotomy and 23-G tunnel entry sclerotomy for PPV with 20% SF6 tamponade surgery.

Experimental and numerical study of the water entry of projectiles at high oblique entry speed

The water entry of cylindrical projectiles at high oblique speed has been investigated experimentally and numerically. Projectiles with three types of noses and different lengths are tested. The projectiles are lunched at different angles, and the development of supercavities are recorded using high-speed camera. During the water entry, deflections occur due to the deviation of the initial velocity and/or the hydrodynamic impact force. The evolution of the supercavities of projectile without deviation is observed. It is found that the collapse of cavity and the generation of new cavity occur alternatively. The motion and the evolution of supercavities at the initial stage of the water entry are simulated through computational fluid dynamics, the typical pressure distributions have been analysed. The drag coefficients are dominated by the nose shape.

Fully nonlinear investigation on water entry of a rigid paraboloid

Oblique water entry of a rigid paraboloid is investigated by fully nonlinear boundary element method. The deadrise angle of the paraboloid increases gradually from zero at the bottom tip and a slenderness coefficient is introduced to symbolize the shape of the paraboloid. Convergence study with respect to time step and element size is carried on to assure the numerical procedure. The free surface elevation and pressure distribution are depicted in time domain. The present solution is compared with the linearized Wagner method and the composite solution with spray jets to investigate the influence of exact fully nonlinear boundary conditions. As there is no sharp edge or tip around the paraboloid, the water flows over the body both from lateral side and down side in oblique entry, the stagnation point relative to the body moves towards the flow-coming direction, and the negative pressure can be observed on both lateral side and down side of the paraboloid. The horizontal speed has great influence on horizontal total force and little influence on vertical total force, while the effect of the slenderness coefficient just has the opposite effect.

Experimental study on the cavity dynamics of oblique impact of sphere on a viscous liquid floating on water

Oblique water entry of marine structure involves complex hydrodynamics phenomena including splash formation, asymmetrical cavity and pinch-off that have been observed in previous systematic experiments. However, very few studies focus on such phenomena induced by oblique impact of object in a two-layer liquid system. In this paper, we present an experimental investigation of oblique entry of a sphere into a deep pool of water within a layer of highly viscous dimethicone floating on the water. In the experiment, a high speed digital camera is established to obtain the instantaneous cavity and motion trajectories for both qualitative and quantitative analysis. The results show that the upper-layer viscous liquid introduces a significant change in the splash formation mechanism and the special behaviors are characterized by stratified splash and corresponding asymmetrical shrinkage structures. Meanwhile, it is observed that the difference in splash characteristics caused by different thicknesses of viscous fluid layer is obvious, and the pinch-off depth is independent of the thickness value which studied in our experiments. In addition, it is found that increasing the horizontal impact velocity will cause a delay in the splash closure and the vertical displacement of the sphere during the dimethicone-water enter process is independent of the horizontal impact velocity. Hydrodynamic force model is established to explain the trajectory of the sphere. Furthermore, the splash angle, pinch-off depth, pinch-off time and the water entry depth at pinch-off locations and the corresponding change tendency are obtained qualitatively and quantitatively. These results indicate that the dimethicone layer is critical in determining the cavity dynamics, especially splash formation and pinch-off characteristics.

On the fully nonlinear water entry of a cone in Stokes wave

Motivated by the wave entry problems of the three-dimensional (3D) ship bow, the paper concentrates on the interaction between an incident wave and a falling cone. The nonlinear 5th order Stokes wave is used to model the undisturbed fluid field, and the wave disturbed by the falling cone satisfies the fully nonlinear boundary conditions. The numerical model is calculated by boundary element method. During the numerical procedure, stretched coordinated system and improved Eulerian method are adopted to trace the highly distorted wave surface. Water entry with different wave heights has been compared with calm water case, oblique entry has been simulated, and the flow behaviors on the up-wave, down-wave and lateral side of the body are investigated. The relative deadrise angle, the relative velocity between body and fluid particles, the propagation direction of the wave as well as the non-uniform distribution of flow velocity are considered together to investigate the 3D pressure field.

Experimental characterization of oblique and asymmetric water entry

Accurate prediction of fluid-structure interactions during water entry is of fundamental importance for the design of planing vessels. However, our understanding of the physics of water entry largely relies on simplified impact conditions, in which the body symmetrically strikes the water surface. In this work, we propose an integrated experimental and theoretical framework to isolate the effects of oblique and asymmetric impact on the water entry of a rigid wedge. Through particle image velocimetry (PIV) and a complementary array of sensors (including position sensors, accelerometers, and pressure sensors), we seek to elucidate the impact dynamics of a wedge and the associated flow physics. In a series of experiments, we systematically analyze the role of the heel and velocity angles on the pile-up evolution, hydrodynamic loading, and energy imparted to the fluid flow. The modified Logvinovich model is extended to study asymmetric and oblique impact for moderate deadrise angles, thereby offering further insight into the physics of the impact. Our results indicate that the heel angle remarkably influences the wedge dynamics, pile-up evolution, and velocity distribution, while the velocity angle has a critical role on the distribution of the hydrodynamic loading. These findings offer evidence for a complex interplay between geometric parameters on the water entry of rigid wedges, which could ultimately improve our understanding of planing vessels operating in real cruise conditions.

Experimental characterization of a direct conversion amorphous selenium detector with thicker conversion layer for dual-energy contrast-enhanced breast imaging.

Dual-energy contrast-enhanced imaging is being investigated as a tool to identify and localize angiogenesis in the breast, a possible indicator of malignant tumors. This imaging technique requires that x-ray images are acquired at energies above the k-shell binding energy of an appropriate radiocontrast agent. Iodinated contrast agents are commonly used for vascular imaging, and require x-ray energies greater than 33 keV. Conventional direct conversion amorphous selenium (a-Se) flat-panel imagers for digital mammography show suboptimal absorption efficiencies at these higher energies. We use spatial-frequency domain image quality metrics to evaluate the performance of a prototype direct conversion flat-panel imager with a thicker a-Se layer, specifically fabricated for dual-energy contrast-enhanced breast imaging. Imaging performance was evaluated in a prototype digital breast tomosynthesis (DBT) system. The spatial resolution, noise characteristics, detective quantum efficiency, and temporal performance of the detector were evaluated for dual-energy imaging for both conventional full-field digital mammography (FFDM) and DBT. The zero-frequency detective quantum efficiency of the prototype detector is improved by approximately 20% over the conventional detector for higher energy beams required for imaging with iodinated contrast agents. The effect of oblique entry of x-rays on spatial resolution does increase with increasing photoconductor thickness, specifically for the most oblique views of a DBT scan. Degradation of spatial resolution due to focal spot motion was also observed. Temporal performance was found to be comparable to conventional mammographic detectors. Increasing the a-Se thickness in direct conversion flat-panel imagers results in better performance for dual-energy contrast-enhanced breast imaging. The reduction in spatial resolution due to oblique entry of x-rays is appreciable in the most extreme clinically relevant cases, but may not profoundly affect reconstructed images due to the algorithms and filters employed. Degradation to projection domain spatial resolution is thus outweighed by the improvement in detective quantum efficiency for high-energy x-rays.

WE‐DE‐207B‐05: Measuring Spatial Resolution in Digital Breast Tomosynthesis: Update of AAPM Task Group 245

Purpose:Spatial resolution in digital breast tomosynthesis (DBT) is affected by inherent/binned detector resolution, oblique entry of x‐rays, and focal spot size/motion; the limited angular range further limits spatial resolution in the depth‐direction. While DBT is being widely adopted clinically, imaging performance metrics and quality control protocols have not been standardized. AAPM Task Group 245 on Tomosynthesis Quality Control has been formed to address this deficiency.Methods:Methods of measuring spatial resolution are evaluated using two prototype quality control phantoms for DBT. Spatial resolution in the detector plane is measured in projection and reconstruction domains using edge‐spread function (ESF), point‐spread function (PSF) and modulation transfer function (MTF). Spatial resolution in the depth‐direction and effective slice thickness are measured in the reconstruction domain using slice sensitivity profile (SSP) and artifact spread function (ASF). An oversampled PSF in the depth‐direction is measured using a 50 µm angulated tungsten wire, from which the MTF is computed. Object‐dependent PSF is derived and compared with ASF. Sensitivity of these measurements to phantom positioning, imaging conditions and reconstruction algorithms is evaluated. Results are compared from systems of varying acquisition geometry (9–25 projections over 15–60°). Dependence of measurements on feature size is investigated.Results:Measurements of spatial resolution using PSF and LSF are shown to depend on feature size; depth‐direction spatial resolution measurements are shown to similarly depend on feature size for ASF, though deconvolution with an object function removes feature size‐dependence. A slanted wire may be used to measure oversampled PSFs, from which MTFs may be computed for both in‐plane and depth‐direction resolution.Conclusion:Spatial resolution measured using PSF is object‐independent with sufficiently small object; MTF is object‐independent. Depth‐direction spatial resolution may be measured directly using MTF or indirectly using ASF or SSP as surrogate measurements. While MTF is object‐independent, it is invalid for nonlinear reconstructions.

A refinement of the Band spreadsheet for wind turbine collision risk allowing for oblique entry

A new spreadsheet is presented, to be used as part of the Band model for estimating potential avian mortality due to wind turbine strike. The spreadsheet extends the Band collision risk spreadsheet by allowing for oblique approach angles and wind speed. The differences in the results between this new spreadsheet and the standard Band spreadsheet are given for two species, the white-tailed eagle Haliaeetus albicilla and the South Island pied oystercatcher Haematopus finschi, chosen for their contrasting sizes and flight characteristics. Under more representative conditions, the true risk for large birds is shown to be substantially greater than that calculated by the Band spreadsheet. Examples of how to use the new spreadsheet with bird survey and wind data are given.