Axial Radius Research Articles

Measurement of scleral curvature using anterior segment optical coherence tomography

AbstractPurpose To work out a way to measuring radius of scleral curvature using anterior segment optical coherence tomography (OCT).Methods Twenty four volunteers were enrolled. With OCT, horizontal and vertical images centered on the visual axis and four images centered on the upper, lower, nasal, and temporal limbus were obtained. To evaluate tangential radius of curvature, we used each nasal and temporal OCT image and calculated the radius of a circle, which passes by three points of scleral surface at 1, 2 and 3 mm from the limbus. To evaluate axial radius of curvature, central horizontal, nasal and temporal OCT images were composed to a new one and the radius of a circle, the center of which is on the visual axis and passes by the point of scleral surface at 2 mm from the limbus, was calculated. The differences in radius of curvature were analyzed by the student t‐test and correlation between two axial radii of curvature calculated by two different reviewers was measured by Pearson correlation coefficient.Results The mean axial radius of nasal curvature (13.33 ± 1.12 mm) was significantly longer than that of temporal curvature (12.32 ± 0.77 mm). The mean tangential radius of nasal curvature (15.14 ± 2.63 mm) was also longer than that of temporal curvature (14.18 ± 2.24 mm). The axial radii of nasal (13.33 ± 1.12 mm) and temporal (12.32 ± 0.77 mm) curvature from one reviewer were very close to those (13.01 ± 1.16 mm and 12.33 ± 0.78 mm) from the other reviewer (Pearson correlation coefficients 0.942 and 0.841, p < 0.001 in both).Conclusion Anterior segment OCT is a useful tool in measuring the radius of scleral curvature. Measurement of axial radius of curvature is more accurate than that of tangential radius of curvature, and has a good reproducibility.

Thermal response of a heat pipe with axially “Ω”-shaped microgrooves

A transient model of capillary flow and heat transfer in a heat pipe with axially “Ω”-shaped microgrooves is developed and numerically analyzed to predict the thermal response characteristics. The transient distributions of the axial capillary radius and solid wall temperature, the evaporating mass rate, the time constant and instantaneous effective thermal conductivity are all investigated and discussed. The results indicate that the rise rate of wall temperature during the initial period is relatively larger, and the coordination of solid wall temperature response among the evaporator, adiabatic and condenser section is realized during the whole startup process. When the input power is increased/decreased, the evaporator temperatures start rising/dropping immediately. In particular, the time constant and instantaneous effective thermal conductivity in the startup process are larger than those in the shutdown process. Additionally, the accuracy of the present model is verified by experimental data obtained in this paper.

Prediction of the effects of constitutive viscoelasticity on stress-diffusion coupling in gels

Modeling of stress/diffusion coupling in gels, originally developed by Doi for the case where the solid component of the gel is a linear elastic network, is here extended to the case of a linear viscoelastic solid component, thereby allowing for a mechanism of intrinsic relaxation. The extended model is solved for a cylindrical gel subjected to unconfined uniaxial compression. Depending on the respective values of the two characteristic times, i.e., diffusive and viscoelastic, measurable quantities like axial force and external radius of the cylindrical gel are calculated to display different qualitative behaviors. Calculated results for the case of uniaxial traction are also reported, which compare favorably with some available experimental results.

The Effect of Disc Radius on Heat Flux and Temperature Distribution in Friction Clutches

Friction clutch is an important machine element, which transmits the torque from the engine to the gearbox. Hence, an accurate estimation of the heat flux and temperatures on the friction surfaces is essential for proper design of the clutch to avoid failure due to thermal stresses. The dimensionless radius ratio (R=inner disc radius/outer disc radius) is the main key quantifying the quantities of heat flux and temperature on friction materials of clutch. Furthermore, the effect of (R) on the axial force, inner and outer radius, peripheral velocity and torque is investigated as well. The MATLAB and ANSYS have been used to perform the numerical calculation in this paper.

An Approach for Analysis of Bulged Profile and Thickness Distribution of Tube in Free Hydro-Bulging Process

Tubular components are widely used in the areas of automotive and aerospace industries due to their excellent properties. A mathematical model considering the bulged region as a parabola curve is proposed to examine the plastic deformation behavior of a thin-walled tube during the free hydro-bulged process. The finite element simulations of the free hydro-bulging process are carried out to verify the approach indirectly. The results indicate that the model is accurate and acceptable to figure out the circumferential radius, wall thickness and axial radius of the bulged profile.

The Role of Axial Length-Corneal Radius of Curvature Ratio in Refractive State Categorization in a Nigerian Population

The aim of this study was to investigate the association of axial length (AL)/corneal radius of curvature (CRC) ratio (AL/CRC) with spherical equivalent refractive state (SER) in young adults. A total of seventy (n = 70) subjects consisting of 31 males and 39 females participated in this study. Subjects were categorized into emmetropia, hyperopia and myopia using the spherical equivalent refraction. The axial length was measured with I-2100 A-Scan ultrasonography/Biometer (CIMA Technology, USA), the corneal radius of curvature with Bausch & Lomb H-135A (Bausch & Lomb Corp., USA), and the refractive state by static retinoscopy and subjective refraction. The mean AL, CRC and AL/CRC ratio of all subjects were 23.74 ± 0.70 mm, 7.84 ± 0.19 mm, and 3.03 ± 0.14, respectively. Myopes had significantly longer AL, steeper CRC and higher AL/CRC ratio than the emmetropes and hyperopes. There was statistically significant inverse correlation between AL and CRC (r = −0.53, P < 0.0001), SER (r = −0.64, P < 0.0001), and between SER and AL/CRC (r = −0.78, P < 0.0001). A significant positive correlation was found between CRC and SER (r = −0.69, P < 0.0001). The categorization of the refractive state of an individual is better done by using the AL/CRC ratio index.

Puroindoline-a, a lipid binding protein from common wheat, spontaneously forms prolate protein micelles in solution

The self-assembly in solution of puroindoline-a (Pin-a), an amphiphilic lipid binding protein from common wheat, was investigated by small angle neutron scattering, dynamic light scattering and size exclusion chromatography. Pin-a was found to form monodisperse prolate ellipsoidal micelles with a major axial radius of 112 ± 4.5 Å and minor axial radius of 40.4 ± 0.18 Å. These protein micelles were formed by the spontaneous self-assembly of 38 Pin-a molecules in solution and were stable over a wide pH range (3.5-11) and at elevated temperatures (20-65 °C). Pin-a micelles could be disrupted upon addition of the non-ionic surfactant dodecyl-β-maltoside, suggesting that the protein self-assembly is driven by hydrophobic forces, consisting of intermolecular interactions between Trp residues located within a well-defined Trp-rich domain of Pin-a.

P.8.a.003 Polypharmacy among psychiatric outpatients in Kuwait

With the disappearance of the radiuscope, alternative methods must be developed to accurately measure gas-permeable (GP) lenses. The purpose of this study was to design, manufacture, and test a novel attachment for the evaluation of spherical base curves of GP rigid contact lenses using a corneal topographer.A topographer attachment was devised with the intent of measuring the surface radii of GP lenses. A front-surface mirror was fixed at a 45° angle above a hemispherical GP lens mount taken from a radiuscope. The device was set in the chin rest of a Humphrey Atlas topographer (Carl Zeiss Meditec, Inc., Jena, Germany) such that the image from the back of a GP surface was focused. The base curve radii of 9 rigid polymer buttons nominally ranging from 5.00 mm to 9.00 mm in 0.5-mm steps were measured 3 times with a Neitz Auto CG (Neitz Instruments Co., Ltd., Tokyo, Japan), Reichert Radiuscope (Reichert Ophthalmic Instruments, Depew, New York), and Humphrey Atlas topographer using the base curve (BC) attachment.An analysis of variance with replication and without interaction, using the main effects of measurement method (n = 5) and nominal button radius (n = 9), found that there was no statistically significant effect of the base curve measurement method (F[4, 122] = 1.23; P = 0.303), although there was a statistically significant effect of nominal button radius (F[8, 122] = 4.70; P = 0.003).Although the optical system of the corneal topographer was designed for measurement of convex surfaces, measurement of base curve radii from concave surfaces was performed without a correction factor using the prototype attachment. The mean SimK and Axial radii were within the tolerance for GP base curve radius, 0.05 mm, cited in ANSI Z80.20-2004 and ISO 18369-2:2006. Thus, the clinical feasibility of this prototype BC attachment to support measurement of spherical base curve radii for GP lenses by a corneal topographer was demonstrated.

Forced translocation of polymer chains through a nanotube: A case of ultrafiltration

Translocation of polymer chains under the application of an external force has been studied through coarse-grained Monte Carlo simulations. The chains are pulled through a nanotube of finite length and diameter and their translocation times measured. The average translocation time, τ follows a scaling relation involving the chain length, N and applied force, F as, τ ∼ N ν′F −μ, where ν′ and μ are two different exponents ( ν′ = 0.674, and μ = 0.95 ± 0.05). The scaling law is closely similar to the nanopore translocation scaling law reported by Milchev et al. [Ann N Y Acad Sci 2009;1161:95]. Characteristic signatures of the chain escape time have been exhibited by the square of end-to-end distance R 2, axial radius of gyration R g−x and other constituent properties. The behavior of the linear polymers under the application of a pulling force has been exploited to gain insights into the ultrafiltration process of unentangled polymers in dilute solution. The generic pulling force–translocation time ( F, τ) data obtained through simulation can be matched reasonably well with the hydrodynamic force–critical macroscopic flow time ( f h, Q c −1) data and also with the hydrodynamic force–reduced critical microscopic flow time ( f h, q c −1) data obtained in the ultrafiltration experiment on long linear polystyrene chains in cyclohexane, as recently reported by Ge et al. [Macromolecules 2009;42:4400] The simulation technique reported here may be extended to study biomolecular transports occurring in long protein channels, as studied experimentally through current–time or voltage–time traces.

Effects of measurement errors on refractive outcomes for pseudophakic eye based on eye model

With the Gullstrand–Le Grand eye model, the effects of various measurement errors on refractive outcomes for pseudophakic eye are studied. An equation to calculate the postoperative refractive error for pseudophakic eyes is derived. The accuracy to get a refractive error less than ca. 25 D is ±0.1 mm for the axial length, ±0.03 mm for the radius of the corneal anterior surface, ±0.12 D for the corneal power and ±0.16 mm for the postoperative anterior chamber depth (ACD). An error of 1 D in intraocular lens (IOL) power leads to a postoperative refractive error of −0.69 D. K-reading leads to a postoperative hyperopia from 0.18 to 0.74 D for eye with different refractive errors previously corrected. The constant velocity in ultrasound biometry assumption overestimates the axial length from 0.17 to 0.31 mm with actual axial length ranging from 21.31 to 32.31 mm. Errors in axial length, corneal power or radius of the corneal anterior surface and postoperative ACD play critical roles in determining the refractive outcomes. The constant-velocity assumption tends to overestimate the axial length. The change of the ratio of corneal anterior to the posterior surface is of minor importance for the overestimation of K-reading.

Prototype base curve attachment for the topographer: What will replace the vanishing radiuscope?

Background With the disappearance of the radiuscope, alternative methods must be developed to accurately measure gas-permeable (GP) lenses. The purpose of this study was to design, manufacture, and test a novel attachment for the evaluation of spherical base curves of GP rigid contact lenses using a corneal topographer. Methods A topographer attachment was devised with the intent of measuring the surface radii of GP lenses. A front-surface mirror was fixed at a 45° angle above a hemispherical GP lens mount taken from a radiuscope. The device was set in the chin rest of a Humphrey Atlas topographer (Carl Zeiss Meditec, Inc., Jena, Germany) such that the image from the back of a GP surface was focused. The base curve radii of 9 rigid polymer buttons nominally ranging from 5.00 mm to 9.00 mm in 0.5-mm steps were measured 3 times with a Neitz Auto CG (Neitz Instruments Co., Ltd., Tokyo, Japan), Reichert Radiuscope (Reichert Ophthalmic Instruments, Depew, New York), and Humphrey Atlas topographer using the base curve (BC) attachment. Results An analysis of variance with replication and without interaction, using the main effects of measurement method (n = 5) and nominal button radius (n = 9), found that there was no statistically significant effect of the base curve measurement method (F[4, 122] = 1.23; P = 0.303), although there was a statistically significant effect of nominal button radius (F[8, 122] = 4.70; P = 0.003). Conclusions Although the optical system of the corneal topographer was designed for measurement of convex surfaces, measurement of base curve radii from concave surfaces was performed without a correction factor using the prototype attachment. The mean SimK and Axial radii were within the tolerance for GP base curve radius, 0.05 mm, cited in ANSI Z80.20-2004 and ISO 18369-2:2006. Thus, the clinical feasibility of this prototype BC attachment to support measurement of spherical base curve radii for GP lenses by a corneal topographer was demonstrated.

Guiding of an electromagnetic pulse in a plasma immersed in combined wiggler and axial magnetic fields

We present a new plasma-based method of guiding an electromagnetic pulse. The scheme consists of an inhomogeneous magnetic field and a uniform density plasma, in contrast to existing schemes that rely on transverse plasma density gradients but need not be magnetized. The refractive index of a magnetized plasma depends on the strength and direction of the magnetic field as well as the plasma density. A guiding channel is formed by using field inhomogeneity to generate the desired transverse profile of the index of refraction. The concept is analyzed with an envelope equation and, for the specific example of a wiggler magnetic field, with a two-dimension particle-in-cell simulation. A simplified model of this scheme as producing a magnetic wall in analogy to metallic waveguides is presented, for which corresponding approximate relations for the guided mode axial wavelength and radius are derived as functions of the plasma and magnetic field parameter. These are seen to be in good agreement with particle-in-cell simulation results. Since the desired inhomogeneity of the refractive index can be made easily when the electromagnetic wave frequency is close to the cyclotron frequency, this guiding scheme is most readily applied in the microwave regime.

Chiral perturbation theory

Chiral perturbation theory is the effective field theory of the strong interactions at low energies. We will give a short introduction to chiral perturbation theory for mesons and will discuss, as an example, the electromagnetic polarizabilities of the pion. These have recently been extracted from an experiment on radiative $\pi^+$ photoproduction from the proton ($\gamma p\to \gamma \pi^+ n$) at the Mainz Microtron MAMI. Next we will turn to the one-baryon sector of chiral perturbation theory and will address the issue of a consistent power counting scheme. As examples of the heavy-baryon framework we will comment on the extraction of the axial radius from pion electroproduction and will discuss the generalized polarizabilities of the proton. Finally, we will discuss two recently proposed manifestly Lorentz-invariant renormalization schemes and illustrate their application in a calculation of the nucleon electromagnetic form factors.

Numerical Simulations of Non-Isothermal Flow in Off-Axis Rotation of a Can Containing a Headspace Bubble

This paper describes numerical simulations of the non-isothermal, laminar flow of Newtonian and non-Newtonian liquids inside rotating cylindrical cans containing a headspace air bubble. Two modes of rotation are considered: axial rotation about a horizontal axis and end-over-end rotation. The rotational speed is held constant so that once initial transients have decayed the flow field in both cases is periodic. The aim of the numerical simulations, carried out using the ANSYS CFX computational fluid dynamics software, is to compare liquid heating times for different flow conditions. To reduce computational run times the calculations are carried out for a liquid with an artificially high value of thermal diffusivity. For axial rotation the simulations have been carried out using 2D and 3D models and it is shown that a 2D model can identify trends in heating times. In both end-over-end and axial modes, rotational speeds and radii of rotation are identified which minimize the heating time. The conditions are shown to correspond closely to those which maximize a measure of mixing in previous studies of isothermal flow.

The Topography of the Central and Peripheral Cornea

To investigate the topography of the central and peripheral cornea in a group of young adult subjects with a range of normal refractive errors. Corneal topography data were acquired for 100 young adult subjects by a method that allows central and peripheral maps to be combined to produce one large, extended corneal topography map. This computer-based method involves matching the common topographical features in the overlapping maps. Corneal height, axial radius of curvature, and axial power data were analyzed. The corneal height data were also fit with Zernike polynomials. Conic fitting to the corneal height data revealed the average apical radius (Ro) was 7.77 +/- 0.2-mm and asphericity (Q) was -0.19 +/- 0.1 for a 6-mm corneal diameter. The conic fit parameters were both found to change significantly for increasing corneal diameters. For a 10-mm corneal diameter, Ro was 7.72 +/- 0.2 mm and Q was -0.36 +/- 0.1. A slight but significant meridional variation was found in Q, with the steepest principal corneal meridian found to flatten at a slightly greater rate than the flattest meridian. The RMS fit error for the conic section was found to increase markedly for larger corneal diameters. Higher-order polynomial fits were needed to fit the peripheral corneal data adequately. Analysis of the axial power data revealed highly significant changes occurring in the corneal best-fit spherocylinder with increasing distance from the corneal center. The peripheral cornea was found to become significantly flatter and to decrease slightly in its toricity. Individual subjects exhibited a range of different patterns of central and peripheral corneal topography. Several of the higher order corneal surface Zernike coefficients were found to change significantly with increasing corneal diameter. Highly significant changes occur in the shape of the cornea in the periphery. On average, the peripheral cornea becomes significantly flatter and slightly less astigmatic than the central cornea. A conic section is a poor estimator of the peripheral cornea.

Effect of Stature and Other Anthropometric Parameters on Eye Size and Refraction in a Population-Based Study of Australian Children

To determine the effect of anthropometric parameters on refraction and ocular biometry. Noncontact methods were used to examine ocular dimensions and cycloplegic refraction in a stratified random cluster sample of year-1 Sydney school students (mean age, 6 years; n = 1765). Height, body weight, and waist circumference were measured according to a standardized protocol. Body mass index (BMI) was subsequently calculated. The percentage of body fat was measured with leg-leg bioelectrical impedance analysis. Associations between parameters were analyzed by multiple linear regression. After adjustment for age in weeks, height was found to be strongly associated with axial length and corneal radius. Children in the 1st quintile for height had axial length of 22.39 +/- 0.04 mm compared with 22.76 +/- 0.04 mm in children in the 5th quintile. Other anthropometric parameters were not associated with axial length or corneal radius. Height was not associated with anterior chamber depth after adjustment for weight. Increases in weight, BMI, and waist circumference were associated with a deeper anterior chamber after adjustment for height. No associations were found between the measured anthropometric parameters and refraction or axial length-corneal radius ratio. This study found a strong association between height and axial length and corneal radius, but not spherical equivalent refraction. The findings may demonstrate the effectiveness of emmetropization in the presence of normal physiological influences.

Flavor twisted boundary conditions and the nucleon axial current

With twisted boundary conditions on the quark fields, we study nucleon matrix elements of the axial current utilizing twisted heavy baryon chiral perturbation theory. One can explore the momentum transfer dependence of the axial form factors more easily than by using ordinary lattice quantized momenta alone. As examples, we derive expressions for the nucleon axial radius and pseudoscalar form factor.

Blood Flow in Stented Arteries: A Parametric Comparison of Strut Design Patterns in Three Dimensions

Restenosis after stent implantation varies with stent design. Alterations in secondary flow patterns and wall shear stress (WSS) can modulate intimal hyperplasia via their effects on platelet and inflammatory cell transport toward the wall, as well as direct effects on the endothelium. Detailed flow characteristics were compared by estimating the WSS in the near-strut region of realistic stent designs using three-dimensional computational fluid dynamics (CFD), under pulsatile high and low flow conditions. The stent geometry employed was characterized by three geometric parameters (axial strut pitch, strut amplitude, and radius of curvature), and by the presence or lack of the longitudinal connector. Stagnation regions were localized around stent struts. The regions of low WSS are larger distal to the strut. Under low flow conditions, the percentage restoration of mean axial WSS between struts was lower than that for the high flow by 10-12%. The largest mean transverse shear stresses were 30-50% of the largest mean axial shear stresses. The percentage restoration in WSS in the models without the longitudinal connector was as much as 11% larger than with the connector The mean axial WSS restoration between the struts was larger for the stent model with larger interstrut spacing. The results indicate that stent design is crucial in determining the fluid mechanical environment in an artery. The sensitivity of flow characteristics to strut configuration could be partially responsible for the dependence of restenosis on stent design. From a fluid dynamics point of view, interstrut spacing should be larger in order to restore the disturbed flow; struts should be oriented to the flow direction in order to reduce the area of flow recirculation. Longitudinal connectors should be used only as necessary, and should be parallel to the axis. These results could guide future stent designs toward reducing restenosis.

Human breast tissue characterisation with small‐angle X‐ray scattering

Small‐angle X‐ray scattering (SAXS) patterns from breast tissue samples are compared with their histology. Formalin fixed human breast tissue specimens containing ductal and lobular carcinoma were studied. Histo‐pathological information is compared with the scattering data, and there is a clear spatial correlation. Supra‐molecular organisation of collagen fibrils is modelled and the model is used to create scattering maps. The model parameters include the axial periodicity (d‐spacing), radius and packing of the fibrils, and these are derived from comparison with the experimental scattering patterns. The d‐spacing is to 0.5% larger in malignant zones of the tumours than in the healthy zones. There are also characteristic differences in the fibril diameter and packing.

Bounds on the tau and muon neutrino vector and axial vector charge radius

A Majorana neutrino is characterized by just one flavor diagonal electromagnetic form factor, the anapole moment, which in the static limit corresponds to the axial vector charge radius $〈{r}_{A}^{2}〉.$ Experimental information on this quantity is scarce, especially in the case of the tau neutrino. We present a comprehensive analysis of the available data on the single photon production process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\nu}\overline{\ensuremath{\nu}}\ensuremath{\gamma}$ off Z resonance, and we discuss the constraints that these measurements can set on $〈{r}_{A}^{2}〉$ for the $\ensuremath{\tau}$ neutrino. We also derive limits for the Dirac case, when the presence of a vector charge radius $〈{r}_{V}^{2}〉$ is allowed. Finally, we comment on additional experimental data on ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ scattering from the NuTeV, E734, CCFR, and CHARM-II Collaborations, and estimate the limits implied for $〈{r}_{A}^{2}〉$ and $〈{r}_{V}^{2}〉$ for the muon neutrino.