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)

Novel integrated tunable laser using filtered feedback for simple and very fast tuning

We present a novel integrated tunable laser based on filtered feedback, which combines a simple tuning method with ns switching speed

Vacuum energy and spectral function sum rules

We reformulate the problem of the cancellation of the ultraviolet divergencies of the vacuum energy, particularly important at the cosmological level, in terms of a saturation of spectral function sum rules which leads to a set of conditions on the spectrum of the fundamental theory. We specialize the approach to both Minkowski and de Sitter space-times and investigate some examples.Comment: 11 pages, revtex4, no figures, version to be published on PR

THE DEVELOPMENT OF LOGISTICS SCIENCE IN RUSSIA

The formation and development of logistics science in Russia has been shown as well as the place occupied in this process by the State University of Management and the Department of Logistics has been revealed. The structure of the scientific school of the Department of Logistics and its relationship with the domestic school of logistics have been shown. An attempt to comprehend critically the directions of development of logistics as a science has been made. The problems of the definition of logistics, discrepancies in the use of this term in scientific and practical activities have been adduced. Perspective directions of the development of modern logistics, developed by the Department of Logistics, have been shown. The system-forming trends in the development of supply chains, determining the further development of logistics as a science and field of activity, have been identified

Fast integrated tunable laser using filtered feedback

A novel integrated tunable laser is presented which combines a simple tuning method with ns switching speed. The Photonic Integrated Circuit consists of a Fabry-Perot laser with deeply-etched DBR mirrors. The Fabry-Perot modes can be selected independently using an Arrayed Waveguide Grating and then re-injected into the laser cavity, forcing single mode operation at the wavelength of that mode. 4ns switching time as well as 15 dB SMSR is demonstrated on the prototype device

Integrated filtered-feedback tunable laser with enhanced control of feedback phase

Recently we presented a novel discretely tunable laser that consists of a Fabry-Perot laser which was forced to operate in single-mode condition by applying on-chip filtered feedback. The laser switches extremely fast (3 ns) and requires simple on/off control currents to switch the wavelength. In these first devices it was not possible to control the phase of the feedback light independently from the feedback intensity. In was solved by adding an extra electrode allowing us to control the phase separately. In this paper we present the new device and study the effect of the control ofthefeedbackphase in order to improve the performance ofthe original tunable laser concept