Rationale for the Choice of the Ellipsoidal Reflector Parameters for Biomedical Photometers

Biomedical photometersʼ information-measuring systems with ellipsoidal reflectors have acceptable results in determining of biological tissues optical properties in the visible and near-infrared spectral range. These photometers make it possible to study the optical radiation propagation in turbid media for direct and inverse problems of light-scattering optics. The purpose of this work is to study the influence of the ellipsoidal reflectors design parameters on the results of biomedical photometry when simulating the optical radiation propagation in a system of biological tissue and reflectors in transmitted and reflected light.The paper substantiates the choice of the ellipsoidal reflectors’ focal parameter for efficient registration of forward and backscattered light. The methodology of the process is illustrated by the results of a model experiment using the Monte Carlo simulation for samples of human brain white and gray matter at the visible range of 405 nm, 532 nm, and 650 nm. The total transmittance, diffuse reflectance, and absorption graphs depending on the sample thickness were obtained. Based on the introduced concepts of the ellipsoidal reflector efficiency index and its efficiency factor, the expediency of choosing the ellipsoidal reflectors focal parameter is analyzed to ensure the registration of the maximum amount of scattered light. The graphs of efficiency index in reflected and transmitted light for different thickness samples of white and gray matter and efficiency factors depending on the sample thickness were obtained.The influence of the reflectors ellipticity on the illuminance of various zones of photometric images using the example of an absorbing biological medium – pig liver tissue – at wavelength of 405 nm with a Monte Carlo simulation was analyzed.The optical properties of biological media (scattering and absorption coefficients, scattering anisotropy factor, refractive index) and the samples’ geometric dimensions, particularly the thickness, are predetermined when choosing the ellipsoidal reflectors parameters for registration of the scattered light. Coordinates of the output of photons and their statistical weight obtained in the Monte Carlo simulation of light propagation in biological tissue have a physical effect on a characteristic scattering spot formation in the receiving plane of a biomedical photometer with ellipsoidal reflectors.

Localised Waves: Tightest Focus, Lorentz Transformation, and Polarization Singularities of Non-Paraxial Beams

<p>I explore the limits of how tightly a beam can be focused, and derive a focal parameter for scalar beams that can be symbolically evaluated for most beams, and is guaranteed to be convergent for physical beams, that compares peak in- tensity to the total intensity in the beam profile. I argue that this parameter is superior to spot size, and use this to derive a rigorous limit of focusing for scalar beams. A particular beam known as the proto-beam achieves this tight- est focus possible. I show the generalisation of this measure to electromagnetic beams, and place a lower bound on the focal extent of electromagnetic beams. I also propose the use of exponential regulators as alternatives to moment based measures, as a solution to the convergence issues created by the power law decay of exact solutions. I explore the Doppler shift for finite beams, and how monochromatic beams become polychromatic under a Lorentz boost. The local frequency is also explored, and I show that a deviation of the local frequency from the Doppler frequency will occur due to wavelength broadening near the focus. Lekner and I examine a beam that closely approximates a paraxial Gaussian beam radially, and examine the phase singularities for optical beams that occur near the zeros of the beams wavefunction. We also investigate attempts to find exact solutions with Gaussian profiles, and show that this is impossible; any such beam will be evanescent and exponentially grow. Finally, I investigate the property of finite classical electromagnetic pulses having a zero momentum frame, and show that for quantum single photon pulses this property holds for the expectation value. I show that any individual measurement however, still measures a light-like four-momentum for the photon.</p>

Localised Waves: Tightest Focus, Lorentz Transformation, and Polarization Singularities of Non-Paraxial Beams

<p>I explore the limits of how tightly a beam can be focused, and derive a focal parameter for scalar beams that can be symbolically evaluated for most beams, and is guaranteed to be convergent for physical beams, that compares peak in- tensity to the total intensity in the beam profile. I argue that this parameter is superior to spot size, and use this to derive a rigorous limit of focusing for scalar beams. A particular beam known as the proto-beam achieves this tight- est focus possible. I show the generalisation of this measure to electromagnetic beams, and place a lower bound on the focal extent of electromagnetic beams. I also propose the use of exponential regulators as alternatives to moment based measures, as a solution to the convergence issues created by the power law decay of exact solutions. I explore the Doppler shift for finite beams, and how monochromatic beams become polychromatic under a Lorentz boost. The local frequency is also explored, and I show that a deviation of the local frequency from the Doppler frequency will occur due to wavelength broadening near the focus. Lekner and I examine a beam that closely approximates a paraxial Gaussian beam radially, and examine the phase singularities for optical beams that occur near the zeros of the beams wavefunction. We also investigate attempts to find exact solutions with Gaussian profiles, and show that this is impossible; any such beam will be evanescent and exponentially grow. Finally, I investigate the property of finite classical electromagnetic pulses having a zero momentum frame, and show that for quantum single photon pulses this property holds for the expectation value. I show that any individual measurement however, still measures a light-like four-momentum for the photon.</p>

Focal parameter analysis of earthquakes of the S-SE of the Iberian Peninsula (1900-1923)

&lt;p&gt;The aim of this study is to make a review, actualization and homogenization of the seismic parameters of the Seismic Catalogue of the National Seismic Network of Spain, which belongs to the National Geographic Institute. Our analysis focusses on the region that spans from 36.0 to 39.5&amp;#176; N and from 3.25&amp;#176; W to 1&amp;#176; E, which is a seismically very active region. The studied time period refers to earthquakes occurred between 1900 and 1923, where most information comes from macroseismic data and macroseismic effects.&lt;/p&gt;&lt;p&gt;The study begins by searching and collecting information from seismic bulletins and seismic catalogues, seismograms, seismic surveys, photographs, specific studies, historical newspapers and different digital archives. Then, the achieved information from all the different sources were reviewed and, whenever possible, the seismic parameters such as localization, seismic intensity and magnitude were recalculated.&lt;/p&gt;&lt;p&gt;The objective of this work is, from one hand, to establish the study methodology that allow to develop an overall review of all the earthquakes occurred in Spain from 1900 to date, and on the other hand, to provide good quality seismic data (improving the completeness and homogeneity of this seismic catalogue). Seismic data is important because it is used to make seismic hazard maps, studies of seismic risk, to update the seismic building standards and it is also used to make seismic characterization of the territory.&lt;/p&gt;

Parameters of the Earth’s rotation taken into account in high-precision simulation of the GLONASS satellites motion in the interests of civil consumers

The purpose of the study was to consider the parameters of the Earth’s rotation in solving the problem of high-precision simulation of the GLONASS navigation spacecraft motion. The paper introduces an algorithm for the operation of a program-algorithm complex for predicting the motion of the GLONASS satellite, taking into account the mathematical models recommended by the International Earth Rotation Service. The study presents the results of estimating the influence of the Earth’s pole motion, uneven rotation of the Earth, precession and nutation on the GLONASS satellite orbit in the form of errors for longitudinal range, vertical and lateral range. The values of the disturbing accelerations and the degree of their influence on the motion of the GLONASS satellite were estimated. The results of deviations of the orbital parameters are obtained: semi-major axis, eccentricity, inclination, longitude of the ascending node, the argument of the pericenter and the focal parameter at an interval of 30 days under the influence of the parameters of the Earth’s orientation.

The Selection of the Reinforcement Scheme for a Parabolic Antenna Made of Composite Materials with an Elliptical Aperture Line

Being prepared foThe problems of designing and calculating reinforced shells of revolution made of composite materials as constituent elements of parabolic antennas with an elliptical aperture line having a focal parameter value of not more than 0.03 m are examined in this paper. The structural layout schemes of reflectors of the parabolic-type mirror spacecraft antennas are reviewed. A technique for designing a bearing frame for reinforcing the reflector shell using numerical analysis based on the finite element method is presented. The technique is based on the assessment of the stiffness parameters of the structural elements of the reflector located between the annular ribs. It utilizes optimization in order to achieve a constant gradient of changes in the stiffness parameters. The deformability of the reflector design that uses a modern high-modulus composite material is evaluated. A finished product is presented as the result of the application of the technique. An assessment of manufacturing and design errors is performed based on the experimental data. The proposed approach to the design of reflectors with an elliptical aperture line eliminates warping of the molded product and deformation during operation such as twisting in the form of a propeller. The results of the study can be used for designing reflectors of spacecraft mirror antennas with a narrow radiation pattern that meet strict requirements of the accuracy of the reflecting surface geometry as well as mass restrictions.

Angular Photometry of Biological Tissue by Ellipsoidal Reflector Method

Angular measurements in optics of biological tissues are used for different applied spectroscopic task for roughness surface control, define of refractive index and for research of optical properties. Purpose of the research is investigation of the reflectance of biologic tissues by the ellipsoidal reflector method under the variable angle of the incident radiation.The research investigates functional features of improved photometry method by ellipsoidal reflectors. The photometric setup with mirror ellipsoid of revolution in reflected light was developed. Theoretical foundations of the design of an ellipsoidal reflector with a specific slot to ensure the input of laser radiation into the object area were presented. Analytical solution for calculating the angles range of incident radiation depending on the eccentricity and focal parameter of the ellipsoid are obtained. Also created the scheme of image processing at angular photometry by ellipsoidal reflector.The research represents results of experimental series for samples of muscle tissues at wavelengths 405 nm, 532 nm, 650 nm. During experiment there were received photometric images on the equipment with such parameters: laser beam incident angles range 12.5–62.5°, ellipsoidal reflector eccentricity 0.6, focal parameter 18 mm, slot width 8 mm.The nature of light scattering by muscle tissues at different wavelengths was represented by graphs for the collimated reflection area. The investigated method allows qualitative estimation of influence of internal or surface layers of biologic tissues optical properties on the light scattering under variable angles of incident radiation by the shape of zone of incident light.

MICROSEISMICITY AND SEISMOTECTONIC PROPERTIES OF THE LEFKADA – KEFALONIA SEISMIC ZONE

Microseismicity, focal–mechanisms, and previously–published focal parameter data are usedto determine the current tectonic activity of the prominent zone of seismicity in Lefkada and KefaloniaIslands. Recordings from a local network installed and operated on the two Islands, aswell as from permanent stations there, were used to obtain accurate microseismicity locations,which in turn is exploited to reveal properties of smaller localized active structures and thelarge–scale crustal faulting. The microseismicity substantially agrees with the historic seismicityand delineates a relatively narrow, major zone of activity that extends along the westerncoasts of both Islands. Cross sections were used in order to provide a detailedcharacterization of the microseismicity and a high–resolution picture of the seismically definedstructures. For the investigation of the past seismic activity relocation of the hypocenters ofolder events was performed, using a reliable velocity model and time delays for the regional stations,calculated on the basis of the accurately determined focal parameters using the localrecordings. The yielding location improvement contributes to the geometry identification of theactive structures, which were previously obscured by location errors, and which constitute acritical input for the study area seismic hazard assessment.