Horizontal Radius Research Articles

Temporal evolution of the corneal curvature in contact lens wearers

In the present work, we have measured the corneal radii in a group of 126 healthy subjects, studying the temporal evolution of these radii after adaptation to contact lenses of polyhydroxyethyl methacrylate with 55% hydration. We measured the horizontal and vertical radii before adaptation, as well as after 3, 6 and 9 months of wearing contact lenses. The decreases were not significant (P < 0.05) in the corneal radii of these subjects; maximum decreases were reached the day after wearing contact lenses, with subsequent recuperation, such that at 9 months the decreases, though persisting, were minimal.

Temporal evolution of the corneal curvature in contact lens wearers

SummaryIn the present work, we have measured the corneal radii in a group of 126 healthy subjects, studying the temporal evolution of these radii after adaptation to contact lenses of polyhydroxyethyl methacrylate with 55% hydration. We measured the horizontal and vertical radii before adaptation, as well as after 3, 6 and 9 months of wearing contact lenses. The decreases were not significant (P &lt; 0.05) in the corneal radii of these subjects; maximum decreases were reached the day after wearing contact lenses, with subsequent recuperation, such that at 9 months the decreases, though persisting, were minimal.

The Joint European Torus (JET) pumped divertor results and their significance for the International Thermonuclear Experimental Reactor (ITER)

The effectiveness of the pumped divertor during the 1994/95 experimental campaign of the Joint European Torus (JET) [P.-H. Rebut, R. J. Bickerton, and B. E. Keen, Nucl. Fusion 25, 1011 (1985)] has allowed the pursuit of a broad-based research program that is highly relevant to the International Thermonuclear Experimental Reactor (ITER) [K. Tomabechi and the ITER Team, Nucl. Fusion 31, 1135 (1991)]. High-performance hot-ion discharges with high confinement (H-modes) free of edge localized modes (ELMs) have set a JET record neutron rate in deuterium, but are limited by various magnetohydrodynamic (MHD) phenomena to βN&amp;lt;1.8, where βN=β/(I/aB), β is the ratio of the plasma pressure to the toroidal field pressure, I is the plasma current, B is the toroidal field, and a is the horizontal minor radius of the plasma. Quasi-steady-state ELMy H-modes have also been studied at high power, high current, and high β. The underlying energy transport exhibits a gyro-Bohm dependence that is lost close to the H-mode threshold and at high β. ELMy H-modes with detached divertor plasmas and radiative power exhaust (the operating regime foreseen for ITER) reduce the power loading to the targets, but at the expense of main plasma confinement and purity. Beryllium has been compared with carbon fiber composite as a divertor target material and melting has been induced at ITER reference off-normal heat loads, but only a moderate degree of self-protection of the beryllium target was found.

Experimental Study of the Spreading of a Viscous Droplet on a Nonviscous Liquid

We describe experiments on the spreading of liquid droplets deposited on a (wettable) liquid substrate, when the friction in the droplet dominates. We find that the horizontal radius R increases wi...

Clinical findings before the onset of myopia in youth. I. Ocular optical components.

A study was conducted to identify variables that were different in children who were emmetropic and became myopic and in children who remained emmetropic. A cohort of initially emmetropic children had eye and vision examinations at 6-month intervals for a period of 3 years. Ocular optical components were measured by keratometry and ultrasonography. Crystalline lens power was calculated using Bennett's formulas. There was a tendency for keratometer power of both principal meridians to be greater in the became-myopic group than in the remained-emmetropic group. Axial length to corneal radius (AL/CR) ratio was significantly greater in the became-myopic group than in the remained-emmetropic group. The variable with the highest sensitivity and specificity was the AL/CR ratio using the horizontal meridian corneal radius. Greater corneal powers and greater AL/CR ratios are risk factors for youth onset myopia.

On the robustness of elastic thickness estimates obtained using the coherence method

In order to uniquely determine the elastic thickness of the lithosphere, Te, from gravity and topography data, the coherence method explicitly assumes that surface and subsurface loads are statistically uncorrelated. In many realistic cases (e.g., mountain building) this assumption is likely to be violated. We present the results of Monte Carlo simulations designed to measure the bias and variance of Te estimates when the degree of correlation, R, between fractal surface and subsurface loads is not null. In this study, R denotes the linear correlation coefficient (Pearson's coefficient), and surface and subsurface loads are self‐affine (fractal). Recording to our results, when there is no correlation between the loads (R = 0), the estimated is in excellent agreement with the simulated Te although its accuracy decreases for increasing plate stiffness. We also find that there is a strong likelihood of an upward bias in estimates if the dimensions of the study area are not adequate to fully resolve the longest wavelengths. This might partially explain why Te values for previous continental studies obtained using the coherence method are often higher than Te values obtained using conventional forward modeling techniques. As the degree of correlation increases, we observe a clear downward bias in the estimated . When surface and subsurface loads are correlated by only a small amount, the fit between the computer‐simulated and predicted coherences is still good for the longest wavelengths within the diagnostic wavebands. In light of these limitations, we use the coherence method to reassess Te estimates for the Alps. Our results indicate that the flexural behavior of the lithosphere to loading does not change significantly along the fold/thrust belt. The similarity between our Te results for the western (30–39 km) and eastern Alps (33–40 km) does not support the hypothesis that Te and the horizontal radius of curvature of mountain belts are correlated.

Acoustic multipole logging in transversely isotropic two-phase medium

An anisotropic reservoir is simulated by a transversely isotropic two-phase medium, and the acoustic field excited by a multipole source in a fluid-filled borehole is investigated. The medium outside the borehole is modeled following Biot’s and homogenization theories. Similar work has only be seen in Schmitt’s [J. Acoust. Soc. Am. 86, 2397–2421 (1989)] study, but he focused his attention on the behavior of the mode waves. In this article, not only are the dispersion and excitation of the mode waves analyzed thoroughly, but the propagation mechanism of the critical refracted P and S waves corresponding to the multipole source branch cut integrations is also investigated for the first time. The effect of the vertical and horizontal permeabilities, porosity, radius, stiffnesses, and other factors on the acoustic field is analyzed.

Modeling Markovian Dependence in Populations of Aralia Nudicaulis

I examined spatial patterns of two populations of the clonal herb Aralia nudicaulis for evidence of spatial inhibition among neighboring ramets. Second—order spatial analysis revealed that ramet patterns of both populations were regular at local spatial scales, a result consistent with the proposition that localized, inter—ramet interactions are important in reducing spatial overlap. Localized ramet interactions suggest Markovian dependence, which is defined when an event (e.g., occurrence of a ramet) at X is dependent solely on the existence or otherwise of an event within a distance ° of X. Evidence of Markovian dependence in the populations was tested by fitting Markov point—process models to the observed ramet patterns. The populations conformed well to the Markov model, the results indicating that both ramet spatial patterns were Markov of range ° = 18 cm. This inhibition distance corresponds closely to the mean horizontal radius of an A. nudicaulis ramet, indicating that interactions occur at the spatial scale of the individual. I suggest that a likely mechanism for the development of locally regular spatial patterns in these populations in inter—ramet competition for a limiting resource, probably light.

垂直下降流のある区画内における乱流拡散火炎上に形成するプリューム性状 : 温度および上昇速度の測定結果

Model fire experiments were carried out to characterize the properties of fire plume given by a diffusion flame in an enclosure with downward air flow. Using methylalcohol as a fuel, a pool fire source providing three different fire size of φ100, 150 or 200mm was used with a downward velocities of .25 and 45 cm/sec. The decreasing mode for both excess temperature and velocity along the vertical flow axis revealed the same modes observed in the free boundary condition. The horizontal plume radius estimated from the temperature showed much wider than that from up-ward velocity distribution in an enclosure with a downward flow. The horizontal distribution of excess temperature was approximated by Gaussian distribution.

Prognostic factors in congenital dislocation of the hip treated with closed reduction. The importance of arthrographic evaluation.

We reviewed the clinical records, arthrograms, and roentgenograms of sixty-one children who had seventy-two congenitally dislocated hips in an effort to identify factors that can be used to predict the outcome of treatment. Only patients who had been followed clinically and roentgenographically for a minimum of two years after the initial closed reduction were included in the study. The mean age at the time of closed reduction was thirteen months (range, three to forty-one months). The mean age at the time of the most recent follow-up was six years (range, two to fifteen years). The mean duration of follow-up after the initial closed reduction was five years (range, two to thirteen years). There was no statistical difference between the good, fair, and poor-result groups with regard to sex, the age at the initial reduction, the traction station, the side of involvement, the initial acetabular index, the initial grade of displacement, the effect of adductor tenotomy, and several of the arthrographic measurements. The medialization ratio (the percentage of the horizontal radius of the cartilaginous femoral head that lay medial to the Perkins line), measured at the time of the reduction, was significantly different (p < 0.04) between the hips for which the result was good or fair and those for which the result was poor. The medialization ratio averaged 75 per cent in the hips for which the result was good, 66 per cent in those for which the result was fair, and 57 per cent in those for which the result was poor. Limbus shapes 5 through 8 were associated with avascular necrosis (p < 0.05) and a poor result (p < 0.03).

Internal wave generation in uniformly stratified fluids. Part 1. Green's function and point sources

In both Boussinesq and non-Boussinesq cases the Green's function of internal gravity waves is calculated, exactly for monochromatic waves and asymptotically for impulsive waves. From its differentiation the pressure and velocity fields generated by a point source are deduced. by the same method the Boussinesq monochromatic and impulsive waves radiated by a pulsating sphere are investigated.Boussinesq monochromatic waves of frequency ω &lt; N are confined between characteristic cones θ = arccos(ω/N) tangent to the source region (N being the buoyancy frequency and θ the observation angle from the vertical). In that zone the point source model is inadequate. For the sphere an explicit form is given for the waves, which describes their conical 1/r½ radial decay and their transverse phase variations.Impulsive waves comprise gravity and buoyancy waves, whose separation process is non-Boussinesq and follows the arrival of an Airy wave. As time t elapses, inside the torus of vertical axis and horizontal radius 2Nt/β for gravity waves and inside the circumscribing cylinder for buoyancy waves, both components become Boussinesq and have wavelengths negligible compared with the scale height 2/β of the stratification. Then, gravity waves are plane propagating waves of frequency N cos θ, and buoyancy waves are radial oscillations of the fluid at frequency N; for the latter, initially propagating waves comparable with gravity waves, the horizontal phase variations have vanished and the amplitude has become insignificant as the Boussinesq zone has been entered. In this zone, outside the torus of vertical axis and horizontal radius Nta, a sphere of radius a [Lt ] 2/β is compact compared with the wavelength of the dominant gravity waves. Inside the torus gravity waves vanish by destructive interference. For the remaining buoyancy oscillations the sphere is compact outside the vertical cylinder circumscribing it, whereas the fluid is quiescent inside this cylinder.

Changes in keratometry following trabeculectomy.

The results of keratometry following trabeculectomy are presented. In contrast to the effects of wound gape after cataract extraction, trabeculectomy produces a reduction in the vertical corneal radius. An initial corresponding increase in horizontal radius is found immediately postoperatively, but this is not apparent by two and seven weeks after surgery. A possible explanation for these findings is proposed.

Decline Curves For Predicting Production Performance From Horizontal Wells

Abstract Most of the equations for predicting the production rates of a horizontal well are based on the assumption of steady-state flow conditions. These equations require an estimation of the horizontal well drainage radius which is not known until the well has been on production and a pressure buildup or drawdown test conducted. Also the steady-state production rate cannot be used to estimate the ultimate recovery of the well. Production decline curves for horizontal wells under various reservoir boundary conditions have been developed using the Green's and source functions. These decline curves can be used to determine the production forecast and the ultimate recovery of a horizontal well. Results of a parameter study using the decline curves also show that wellbore stimulation, well spacing and length are probably the most important factors determining the effectiveness of a horizontal well. Introduction Production forecasts are required to evaluate the economics of a horizontal well project. Reliable production forecasts are most needed during the early stage of the project when the horizontal well has not yet been drilled and only a minimum amount of geological data is available. In a recent literature survey, we found more than twenty papers on the prediction of horizontal well productivity. The most widely used methods are the steady-state equations published by Giger(1), Borisov(2), Joshi(3) and others. These equations require an estimation of the horizontal well drainage radius which is not known until the well has been on production and a pressure buildup or drawdown test conducted. The assumption of steady-state flow condition is valid only for a reservoir with a constant pressure applied at the outer boundary such as the water flood recovery process. Also, it is not possible to estimate the ultimate recovery from a bounded reservoir using the steady-state production rates. Recently, several horizontal well analytical models have been developed which do not require the assumption of the drainage radius and are not based on the steady-state Darcy's equation. Babu(4) presented an equation for calculating the productivity of a horizontal well in a bounded reservoir during pseudo steady-state flow. Its application requires the determination of two parameters. The first is the geometric factor which accounts for the effect of anisotropic permeability, the well location and the drainage area. The second is the skin factor which accounts for the effect of well length. Similarly, Kuchuk et al. (5) developed an equation for predicting the inflow performance of a horizontal well in a bounded rectangular reservoir which is influenced by the presence of a gas cap of bottomwater sand. The inflow performance is calculated using the long time approximation to the analytical solutions of a three-dimensional reservoir problem. Duda(6) and Chang(7) developed type curves for predicting the cumulative production of a horizontal well using the numerical simulation results. In the formulation of the numerical models, the wellbore is represented by grid blocks much larger than its diameter and the wellbore transmissibility must be approximated using simplified analytical equations. For example, Chang used an analytical equation developed by Abou-Kassem and Aziz(8) to estimate the wellbore transmissibility.

Equation in complex variable of axisymmetrical deformation problems for a general shell of revolution

In this paper, the equation of axisymmetrical deformation problems for a general shell of revolution is derived in one complex variable under the usual Love-Kirchhoff assumption. In the case of circular ring shells, this equation may be simplified into the equation given by F.Tolke(1938)[3], R.A.Clark(1950)[4]and V.V.Novozhilov(1951)[5]. When the horizontal radius of the shell of revolution is much larger than the average radius of curvature of meridian curve, this equation in complex variable may be simplified into the equation for slander ring shells. If the ring shell is circular in shape, then this equation can be reduced into the equation in complex variable for slander circular ring shells given by this author (1979)[6]. If the form of elliptic cross-section is near a circle, then the equation of slander ring shell with near-circle ellipitic cross-section may be reduced to the complex variable equation similar in form for circular slander ring shells.

Directivity of an acoustic monopole in a floating ice plate and implications to Arctic ambient noise

Predictions were made of the directivity of higher‐frequency (1‐kHz) acoustic radiation into the water from a monopole source located in a floating ice plate (2.4 m thick). Theoretical calculations were conducted using the SAFARI propagation routine [H. Schmidt and J. Glattetre, J. Acoust. Soc. Am. 78, 2105–2114 (1985)] and by the method of steepest descents (P. J. Stein, “Monopole Source in a Floating Ice Plate,” MIT/WHOI Ph.D. thesis, 1986). The models show close agreement with each other and predict a strong downward directivity with most of the energy radiated at grazing angles greater than 70°. This implies that (1) higher‐frequency impulsive ice noises detected at an omnidirectional hydrophone are likely radiated from a relatively small area of ice directly above the receiver (the area increasing with receiver depth) and (2) the nonimpulsive (background) ambient noise at higher frequencies is dominated by radiation from ice events located within a horizontal range radius equal to roughly one water depth. Modeling also shows that nulls can occur for some radiation angles for particular source depths within the ice. Also, only small effects of a more realistic ice strength vertical profile over a uniform profile are seen. [Work supported by ONR.]

Beta limit of crescent and bean shaped tokamaks

The maximum attainable beta values which can be expected in tokamaks with crescent (BEAN 1) and rounded (BEAN 2) bean shaped cross-sections are obtained numerically by using the linear ideal MHD stability analysis code ERATO. The current profiles are optimized with a fixed pressure profile for high values of beta, keeping Mercier, high-n ballooning and n = 1 kink modes stable. The poloidal plasma cross-sections are inscribed in a rectangle with an aspect ratio of three and an ellipticity of two. A confocal wall, the distance of which from the plasma surface is equal to the horizontal minor plasma radius, is present to stabilize against the kink mode. Depending on the shape and triangularity (indentation), a beta value of 10 to 17% is obtained. It is also shown that the coefficient of the Troyon-type beta scaling increases for an indented plasma. In the case of small indentation, the BEAN 1 type tokamaks show higher beta values than the BEAN 2 type. For strong indentation, the BEAN 2 type gives the highest beta value.

Formation of collapse calderas

Collapse calderas are common in many volcanic regions, but the mechanics of their formation is not well understood. I propose that collapse calderas may form as a result of the growth of associated shallow magma chambers. Excess magmatic pressure in a shallow chamber gives rise to tensile stresses at the surface, but the location and magnitude of the maximum tensile stress depend on the shape of and depth ( d ) to the top of the chamber. This model indicates that penny-shaped chambers, i.e., sill-like chambers of circular horizontal cross sections, are most likely to initiate collapse calderas. For such a chamber with horizontal radius a , the higher the a/d (radius/depth) ratio, the greater the probability of forming a collapse caldera.

Distributions of cumulative displacement and seismic slip on a single normal fault surface

Displacement profiles (normalized displacement vs normalized distance from the point of maximum displacement) have been plotted for 34 horizontal radii from 25 normal faults with maximum displacements ranging from 1.0 to 37.5 m. The composite displacement profile for these faults, when corrected for systematic inaccuracies of the data, is significantly different from the theoretical slip profile for a single seismic slip event. The integration of slip displacement profiles of many slip events on a growing fault shows that a steady-state displacement profile will be established. This theoretical displacement profile is similar to the composite profile derived from the fault data. Analysis of displacement data from 488 fault traces, which do not necessarily pass through the point of maximum displacement of their respective faults, shows that although displacement measurements are strongly influenced by ductile drag the theoretical distribution can still be identified in the data. Although the slip distribution on a fault during a single slip event, or during a period of stable sliding, is not simply related to the distribution of cumulative displacement on the fault, a knowledge of both characteristics places firm constraints on fault growth models.

Use of an Elliptical Aperture to Control Saturation in Closely-Coupled, Cold Iron, Superconducting Dipole Magnets

The high fields permitted by superconducting windings result in saturation of closely-coupled iron in dipole and quadrupole beam transport magnets. Coupland1 suggested using a triangular cutout at the poles to reduce the change in the sextupole (b2) term due to saturation. The use of an elliptical aperture in a close-coupled dipole for the Relativistic Heavy Ion Collider (RHIC) has been studied using the BNL computer program MDP (a version of GFUN). The ellipse aspect ratio was varied while holding the horizontal (minor) radius constant. The proper aspect ratio gives no shift in b2 due to saturation, and a reduction in the b4 shift. A modification of the ellipse also reduces b4. The elliptical aperture introduces a large b2 term at low field which must be compensated for by the coil design. A practical coil design which does this for the RHIC magnet is presented.

Calculation and application of the anterior surface area of a model human cornea

The macroscopic anterior surface area was calculated for three models of the average human cornea. Two models, a general ellipsoid and a rotational ellipse (rotationally symmetric ellipsoid) gave a surface area of 132 mm2, while a spherical model gave 126 mm2. A general ellipsoidal model having the maximum radius horizontal (with-the-rule corneal astigmatism) has less surface area than a rotational ellipse with the same horizontal radius. For a corneal sagittal height of 2.59 mm, the surface area of an ellipsoidal cornea equals -19.2Q + 16.3R -0.476 which specifies a rotational ellipse (radius R, asphericity Q) of equal surface area. In a cornea with the maximum radius vertical (against-the-rule corneal astigmatism), the ellipsoid has slightly more surface area than a rotational ellipse with the same horizontal radius of curvature. For a given horizontal radius of curvature, the sphere has the lowest surface area. For a corneal sagittal height s of 2.59 mm, the sphere underestimates by 8% the surface area of a rotational ellipse with asphericity -0.5. The anterior corneal surface area of a rotational ellipse model, radius R, asphericity Q is given by 2 pi Rs- 19.2Q. In all three models, the surface area increases with horizontal radius of curvature. In the rotational ellipse model, the rate of increase (slope) is independent of asphericity, and the slope found in with-the-rule astigmatism is less than the slope found with against-the-rule astigmatism. The calculated surface area predicts a precorneal tear volume of 0.86 microliter for a 6.5 micron tear thickness. The apparent, or plane projected are of an epithelial lesion underestimates the curved surface area with a percentage error that increases rapidly with lesion diameter. For a 12 mm diameter lesion on a rotational ellipse model, the apparent area underestimates the surface area by 18%. The average posterior corneal surface in human is not spherical but imitates the anterior surface, and has an area of 137 mm2 or 3.8% greater than the anterior area.