Accurate whole-spectrum measurements of intracellular pH and [Na+]

Fluorescent measurements of intracellular H⁺ and Na⁺ are improved by using whole spectra of the fluorescent indicators BCECF and SBFI, respectively. The extra data in whole spectra enable both an accurate calibration and a ready detection of artifacts which are not possible to identify using a more conventional data analysis that relies upon only two wavelength windows in the fluorescence spectra. The whole-spectrum technique is applicable to cell suspensions in a conventional fluorimeter (as is reported here with SBFI), as well as to attached cells using a fluorimeter combined with an inverted epifluorescence microscope. The spectral method was highly reproducible in that pairs of successive pH measurements differed, on average, by only 0.01±0.02 U. Random uncertainty from sample to sample was estimated numerically from the standard deviation of measurements on ionophore-treated cells. When full-spectrum analysis was employed, this scatter showed a two-fold improvement over results obtained using the two-wavelength ratio method. Because SBFI has a relatively narrow dynamic range, whole-spectrum analysis has been applied to improve the accuracy of sodium determinations. The calibrated system measured [Na⁺]_i with excellent linearity over the range 2–150 mM and with an accuracy of approximately 5 mM.     

Obtaining the bidirectional transmittance distribution function of isotropically scattering materials using an integrating sphere

This paper demonstrates a method to determine the bidirectional transmittance distribution function (BTDF) using an integrating sphere. Information about the sample’s angle-dependent scattering is obtained by making transmittance measurements with the sample at different distances from the integrating sphere. Knowledge about the illuminated area of the sample and the geometry of the sphere port in combination with the measured data combines to a system of equations that includes the angle-dependent transmittance.The resulting system of equations is an ill-posed problem which rarely gives a physical solution. A solvable system is obtained by using Tikhonov regularization on the ill-posed problem. The solution to this system can then be used to obtain the BTDF.Four bulk-scattering samples were characterised using two goniophotometers and the described method to verify the validity of the new method. The agreement shown is excellent for the more diffuse samples. The solution to the low-scattering samples contains unphysical oscillations, but still gives the correct shape of the solution. The origin of the oscillations and why they are more prominent in low-scattering samples are discussed.     

Evaluation of adhesive and elastic properties of materials by depth-sensing indentation of spheres

Work of adhesion is the crucial material parameter for application of theories of adhesive contact. It is usually determined by experimental techniques based on the direct measurements of pull-off force of a sphere. These measurements are unstable due to instability of the load-displacement diagrams at tension, and they can be greatly affected by roughness of contacting solids. We show how the values of work of adhesion and elastic contact modulus of materials may be quantified using a new indirect approach (the Borodich?CGalanov (BG) method) based on an inverse analysis of a stable region of the force-displacements curve obtained from the depth-sensing indentation of a sphere into an elastic sample. Using numerical simulations it is shown that the BG method is simple and robust. The crucial difference between the proposed method and the standard direct experimental techniques is that the BG method may be applied only to compressive parts of the force-displacements curves. Finally, the work of adhesion and the elastic modulus of soft polymer (polyvinylsiloxane) samples are extracted from experimental load-displacement diagrams.     

Linear method for evaluation of radius of spherical surface from discrete set of data points

Our work deals with the problem of evaluation of the spherical surface parameters from the discrete set of measured data points. We propose a new linear method for determination of the center and the radius of curvature of the measured spherical surface. Such method can be used for evaluation of the measurements obtained from both contact and noncontact 3D coordinate measuring machines. We perform an analysis of the proposed sphere fitting method and we verify that the obtained results are comparable to results calculated using existing techniques. Finally, the proposed algorithm is implemented for evaluation of real measurements of spherical optical surfaces using the designed scanning chromatic confocal system.     

Applications of the Poincaré sphere in polarization metrology

The Poincaré sphere representation of polarization states is used to derive two auxiliary equations for phase retardance measurements. These equations, in addition to another two previously derived equations, allow for extending the range of validity of a model for calibrating phase plates in pairs. In another application, the sphere is used to explain a new method for identifying the principal axes of two birefringent phase plates during their calibration.     

Reflectance measurements of aluminium surfaces using integrating spheres

In the investigation of the considerable absorption of visible light in industrially rolled aluminium surfaces, a thorough knowledge of the total reflectance measurement method is required. In this paper a general introduction to the integrating sphere method is given, with emphasis on the current understanding of instrumental artefacts and ways of correcting them. Selected aluminium surfaces were measured employing two spheres; a single-beam instrument equipped with a white-light source and a Si-photoelement detector, and a double-beam sphere, which measures reflectance properties with spectral resolution. It was found necessary to take precautions concerning the orientation of rolled samples relative instrument geometry, to avoid artificial losses from the sphere. The use of a specular reference standard is assumed to minimise the effect of several sphere artefacts, since it produces similar angular distribution of reflected light as the rather glossy aluminium samples. Measurements with spectral resolution show that the total reflectance of aluminium is somewhat red shifted after rolling, a tendency that cannot be revealed in ordinary white-light measurements.     

The diffraction of sound by an impedance sphere in the vicinity of a ground surface

The problem of sound diffraction by an absorbing sphere due to a monopole point source was investigated. The theoretical models were extended to consider the case of sound diffraction by an absorbing sphere with a locally reacting boundary or an extended reaction boundary placed above an outdoor ground surface of finite impedance. The separation of variables techniques and appropriate wave field expansions were used to derive the analytical solutions. By adopting an image method, the solutions could be formulated to account for the multiple scattering of sound between the sphere and its image near a flat acoustically hard or an impedance ground. The effect of ground on the reflected sound fields was incorporated in the theoretical model by employing an approximate analytical solution known as the Weyl-van der Pol formula. An approximation solution was suggested to determine the scattering coefficients from a set of linearly coupled complex equations for an absorbing sphere not too close to the ground. The approximate method substantially reduced the computational time for calculating the sound field. Preliminary measurements were conducted to characterize the acoustical properties of an absorbing sphere made of open cell polyurethane foam. Subsequent experiments were carried out to demonstrate the validity of the proposed theoretical models for various source/receiver configurations around the sphere above an acoustically hard ground and an impedance ground. Satisfactory comparative results were obtained between the theoretical predictions and experimental data. It was found that the theoretical predictions derived from the approximate solution agreed well with the results obtained by using the exact solutions.     

Numerical investigation of measurement error of the integrating sphere based on the Monte-Carlo method

To accurately measure the directional-hemispherical reflectance of a material surface using an integrating sphere, we investigated the effects of the integrating sphere’s interior structure and coating properties on the measured data by numerical simulation. The results showed that the integrating sphere’s structure and the reflectance of the coating codetermine the accuracy of the measured results. When the integrating sphere’s structure is fixed, choosing an appropriate internal coating using the method proposed in this paper ensures the accuracy of the results. If a proper coating is not available, we propose a method to effectively correct the measured results.     

Weather radar calibration by means of the metallic sphere and multiparameter radar measurements

Summary Absolute calibration is an important task in order to obtain reliable and accurate measurements of radar observables and derived meteorological parameters. In this paper two procedures are described; the first one is based on measuring the power received from a metallic sphere and the second utilizes the rainfall estimates obtained by the multiparameter radar measurements. The accuracy of the latter method is studied in detail from the simulation of the dual polarization measurables. The theoretical results are compared with radar measurements relative to a rain event.     

Diffuse surface calibration method to improve accuracy and dynamic range of aerosol elastic light scattering measurements

A new method to calibrate detectors for elastic light scattering (ELS) measurement based on diffuse scattering from a Lambertian surface is presented. The method produces a calibration signal that is approximately seven orders of magnitude larger than a propane gas Rayleigh scattering calibration. The method also allows for calibration of detectors such as photodiodes, which are not sensitive enough to detect Rayleigh scattering for calibration but possess characteristics desirable for the measurement of soot ELS. Since the method is only suitable for backward scattering calibrations, transfer of calibration data from a backward- to a forward-oriented detector is accomplished with a secondary laser and integrating sphere. In demonstration experiments, calibration constants for photomultiplier tube (PMT) detectors obtained using both Rayleigh scattering and diffuse surface scattering agreed within experimental uncertainties as did measurements of in-flame scattering coefficients obtained with PMTs and photodiodes. However, achievable uncertainties with the diffuse-surface calibration approach were significantly reduced. More importantly, by enabling the use of photodiode detectors in ELS measurements, the new method facilitates operation at higher photon fluxes resulting in improved signal-to-noise ratios, reduced influence of photon shot noise, and the ability to achieve higher dynamic range in transient measurements.     

低损耗薄膜背散仪吸光器的关键技术研究

激光高反射膜片的背散光大小直接影响激光陀螺的精度,低损耗薄膜背散仪是在全积分散射测试理论及立体角积分散射测量原理的基础上提出的一种测量高反射膜片背散光的新方法.在低损耗薄膜背散仪的设计中,吸光器的吸光装置结构及吸光材料的选择直接影响着测量精度.计算表明,在用波长λ=632.8nm、激光功率P=10mW的氦氖激光照射至与...     

On the validity of constraints on light elementary particles and extra-dimensional physics from the Casimir effect

We discuss the constraints on the parameters of a Yukawa interaction obtained from the indirect measurements of the Casimir pressure between parallel plates using the sphere–plate configuration. Recently, it was claimed in the literature that the application of the proximity force approximation (PFA) to the calculation of a Yukawa interaction in the sphere–plate configuration could lead to a large error of order 100% in the constraints obtained. Here we re-calculate the constraints both exactly and using the PFA, and arrive at identical results. We elucidate the reasons why an incorrect conclusion was obtained suggesting that the PFA is inapplicable to calculate the Yukawa force.     

Effect of detailed cell structure on light scattering distribution: FDTD study of a B-cell with 3D structure constructed from confocal images

Human B-cells play an important role in the immune system, and because of their relatively simple structures with a nearly spherically shaped cell membrane and a large nucleus, they provide a good case to study on how the details of cell structure affect light scattering properties. A finite-difference-time-domain (FDTD) method is used to calculate angle-resolved light scattering distributions from a B-cell. Published FDTD simulations to date have used a smooth shape with a certain degree of symmetry to approximate the actual cell shape. In contrast, for this work, the shapes of the cell and its nucleus were determined from confocal microscopy measurements. An automated procedure was developed to construct a realistic three-dimensional structure of a B-cell from a stack of two-dimensional confocal images. The angle-resolved Mueller matrix elements of the B-cell were calculated and averaged for 30 different angles of incidence using a parallel FDTD code. These results were compared with those from a homogeneous and a coated sphere. Scattering from the two sphere models and the B-cell were very similar for scattering angles less than 5°, and the coated sphere and B-cell agreed well for scattering angles up to 20°. However, at larger angles, the scattering from the B-cell was a much smoother function of angle than scattering from either sphere model. Additionally, the homogeneous sphere results were the most similar to the B-cell results for most angles between 120° and 150°, and at angles greater than 150°, the B-cell scattered more light than either of the spheres. These results yield strong evidence that accurate modeling of light scattering by biological cells requires not only the high accuracy of the employed numerical method but the realistic cellular structure as input information as well.     

Temperature-dependent absorptance of painted aluminum, stainless steel 304, and titanium for 1.07 μm and 10.6 μm laser beams

We measured the temperature-dependent absorptance of metals (Al, Ti, SS304) for continuous beams from 1.07 μm fiber laser and 10.6 μm CO₂ laser using power sensors and infrared (IR) pyrometers. The absorptance measurements were repeated for metals with three different paint coatings. For measurements at elevated temperatures up to the melting point, integrating sphere is not practical since high temperature radiation from a heated target disturbs weak output from the sphere considerably. Our results provide how each metal, whether coated or uncoated, absorbs the infrared beams as temperature is elevated to a melting point. A polynomial approximation to the measured absorptance of each target is provided for modeling of the laser-metal interaction at elevated temperatures.     

Loss measurements in graded-index compound-glass fibers

The optical fiber scattering loss coefficient is measured directly in a scattering sphere or deduced indirectly from total loss measurements. The results show agreement for graded-index silica-based fibers, but they seem conflicting for graded-index compound-glass fibers. This is explained from the diffusion-controlled refractive index profile and the ensuing mode-dependent scattering and absorption loss due to the different optical properties of core and cladding glass. Using this model the two-lengths total loss measurement method is discussed. A detailed experiment is described that convincingly illustrates the mode of operation of the scattering sphere as used in daily practice. The wavelength-independent term in the total loss, different for fibers drawn from the same glass, is explained as being scattering partly due to 1-mode mixing of modes with the same β by imperfections that affect high-1-modes predominantly. The total loss of the glasses to be investigated can be measured using low NA excited silicone-clad fibers and safely can be decomposed into scattering and absorption contributions.     

First application of the real space linear muffin-tin orbital atomic sphere approximation method for calculating Fermi contact hyperfine fields

In this work we apply the recently developed first-principles real space linear muffin-tin orbital atomic sphere approximation (RS-LMTO-ASA) scheme to calculate the hyperfine field for 3d impurities (V, Cr, Mn andFe) in Cu. We obtain the Fermi contact term at the impurities andat four shells of host atoms around the impurities. We compare our results with theoretical values obtained using the KKR-Green-function method andwith NMR measurements. The overall agreement is excellent, confirming the reliability of the RS-LMTO-ASA approach as means of obtaining information on hyperfine fields.     

Loss measurements in graded-index compound-glass fibers

The optical fiber scattering loss coefficient is measured directly in a scattering sphere or deduced indirectly from total loss measurements. The results show agreement for graded-index silica-based fibers, but they seem conflicting for graded-index compound-glass fibers. This is explained from the diffusion-controlled refractive index profile and the ensuing mode-dependent scattering and absorption loss due to the different optical properties of core and cladding glass. Using this model the two-lengths total loss measurement method is discussed. A detailed experiment is described that convincingly illustrates the mode of operation of the scattering sphere as used in daily practice. The wavelength-independent term in the total loss, different for fibers drawn from the same glass, is explained as being scattering partly due to 1-mode mixing of modes with the same β by imperfections that affect high-1-modes predominantly. The total loss of the glasses to be investigated can be measured using low NA excited silicone-clad fibers and safely can be decomposed into scattering and absorption contributions.     

CoFe2O4/空心微球复合体的制备与吸波性能

采用化学共沉淀法,在空心微球上包覆一层CoFe2O4,得到一种低密度的空心磁性微球．磁测量结果表明,磁场下退火制备的CoFe2O4样品反位缺陷减少,从而导致饱和磁化强度随退火磁场的增强而增大．吸波性能测试结果表明,包覆结构的CoFe2O4/空心球样品是一种轻质的微波吸收材料.     

CoFe_2O_4/空心微球复合体的制备与吸波性能

采用化学共沉淀法,在空心微球上包覆一层CoFe2O4,得到一种低密度的空心磁性微球.磁测量结果表明,磁场下退火制备的CoFe2O4样品反位缺陷减少,从而导致饱和磁化强度随退火磁场的增强而增大.吸波性能测试结果表明,包覆结构的CoFe2O4/空心球样品是一种轻质的微波吸收材料.     

Interpretation of Light Scattering Spectra of Dispersions – A Hybrid Approach to Account for Interparticle Interactions

The problem of extracting quantitative information on individual particle properties from spectroscopic measurements conducted at concentrations where particle interactions become significant is of great industrial and theoretical importance. For dispersions of charged particles, this can happen at fairly low concentrations. The effect of the fluid (slurry) structure has to be taken into account to interpret the light scattering spectra of such dispersions. In this paper, a hybrid method that addresses the effect of the fluid structure is proposed. The hybrid approach describes the fluid structure by relating the “effective” Percus‐Yevick hard‐sphere parameters to the system parameters using empirical models. The feasibility of this approach is examined through a theoretical study with data generated by Monte Carlo simulations of a monodisperse dispersion of charged spherical particles using realistic interaction potentials under single scattering conditions.