Biomechanical analysis of parameters influencing pressure-volume relationship in the human eye

Purpose: To study the effects of different mechanical properties of the sclera and the cornea, such as their anisotropy, non-uniformity, and deflections in their spherical shapes on pressure-volume relationship. Methods: Correlations between the intraocular pressure (IOP) and the intraocular volume (IOV) were found for spherical and ellipsoidal orthotropic layers by means of 3D-theory of elasticity. Subsequently, the corneoscleral shell of the eye was modeled as a conjugated shell consisting of two segments. The sclera and the cornea are generally assumed to be the parts of the orthotropic elliptic shells with different geometrical and mechanical properties. Relationship between IOP and IOV was obtained for three mechanical models with following problem statements: 1) sclera and cornea are assumed to be soft shells; 2) sclera and cornea are supposedto be orthotropic shells with small modules of elasticity in the thickness direction; for this model calculations were made due to applied shell theory by Chernykh; 3) sclera and cornea are modeled as 3D elastic solids with FEM/ANSYS (ANSYS, Inc.,Canonsburg, PA). The calculations were performed for different sets of parameters for all three mechanical models and were compared to clinical data. Results: Transversal isotropic shells of revolution of different shapes (modelling the sclera) with equal initial volumes showed linear pressure-volume relationship, while proportionality factor (K) is minimal for a spherical shell (emmetropic eye).If the ratio of the axial length (AL) and the equatorial diameter of the shell (D) increases (the case of a shell modelling a myopic eye), then factor K increases up to 5-10%. If the ratio AL/D decreases (for a shell modelling a hyperopic eye), then factorK starkly increases up to 100%. The same effect was observed for the 2-segments model. Conclusions: Both the orthotropic properties of the sclera (the ratio of two tangential modules of elasticity) and the non-uniformity of the sclera have a significant effect on the character of the pressure-volume relationship and, thus, on the rigidity of the human eye. Geometric and elastic properties of the cornea also affect the relationship, although to the less extent

Optical response of a cold-electron bolometer array

A multielement bolometric receiver system has been developed to measure the power and polarization of radiation at a calculated frequency of 345 GHz. Arrays of ten series-parallel connected cold-electron bolometers have been pairwise integrated into orthogonal ports of a cross-slot antenna. Arrays are connected in parallel in the high-frequency input signal and in series in the output signal, which is measured at a low frequency, and in a dc bias. Such an array makes it possible to increase the output resistance by two orders of magnitude as compared to an individual bolometer under the same conditions of high-frequency matching and to optimize the matching with the JFET amplifier impedance up to dozens of megohms. Parallel connection ensures matching of the input signal to the cross-slot antenna with an impedance of 30 Omega on a massive silicon dielectric lens. At a temperature of 100 mK, a response to the thermal radiation of a thermal radiation source with an emissivity of 0.3, which covers the input aperture of the antenna and is heated to 3 K, is 25 mu V/K. Taking into account real noise, the optical fluctuation dc sensitivity is 5 mK, the estimated sensitivity corresponding to the noise of the amplifier is about 10(-4) K/Hz(1/2), and the noise-equivalent power is about (1-5) x 10(-17) W/Hz(1/2)

Lateral distribution of high energy muons in EAS of sizes Ne approximately equals 10(5) and Ne approximately equals 10(6)

Muon energy spectra and muon lateral distribution in EAS were investigated with the underground magnetic spectrometer working as a part of the extensive air showers (EAS) array. For every registered muon the data on EAS are analyzed and the following EAS parameters are obtained, size N sub e, distance r from the shower axis to muon, age parameter s. The number of muons with energy over some threshold E associated to EAS of fixed parameters are measured, I sub reg. To obtain traditional characteristics, muon flux densities as a function of the distance r and muon energy E, muon lateral distribution and energy spectra are discussed for hadron-nucleus interaction model and composition of primary cosmic rays