Mean Refractive Index Research Articles

Analysis of hen egg white lysozyme adsorption on Si(Ti)O 2 ∣ aqueous solution interfaces at low ionic strength: a biphasic reaction related to solution self-association

Adsorption kinetics of hen-egg white lysozyme at concentrations of 10 −7, 10 −6, 10 −4 M and at pH 8.0 have been measured on Si 0.8Ti 0.2O 2 surfaces by means of optical waveguide lightmode spectroscopy and were found to proceed in two distinct kinetic régimes: a fast and quasi linear increase of the surface concentration followed by slower kinetics that could be described qualitatively by the theory of random sequential adsorption. The transition between these two kinetic régimes was correlated with abrupt changes in the values of the mean refractive index and of the thickness of the adsorbed layer as well as in the desorption kinetics performed either before or after the transition from the first régime to the second. Experiments carried out at the same ionic strength but at different pH values showed that the adsorption behaviour of lysozyme is related to its self-association properties in highly concentrated solutions.

Influence of oxygen pressure on structural and optical properties of Al 2 O 3 optical waveguides prepared by pulsed laser deposition

Pure and europium doped alumina waveguides have been prepared by Pulsed Laser Deposition using a KrF excimer laser at oxygen pressures in the range from 10-7 to 0.1 mbar. The composition of the films and the doping ion concentration were determined by Rutherford Backscattering Spectroscopy. From X-ray diffraction measurements, a progressive growth of γ-Al2O3 crystallites is observed as the oxygen pressure decreases. After annealing treatment, the alumina films are constituted of α-Al2O3 crystallites while europium doped alumina films remain constituted of γ-Al2O3 crystallites. The films have optical waveguiding properties. The mean refractive index of the film increases as oxygen pressure decreases.

Use of mean platelet component to measure platelet activation on the ADVIA 120 haematology system

Platelet activation results in changes in a number of cell surface molecules including an increase in P-Selectin (CD62P) that may be rapidly and conveniently measured by immunofluorescent flow cytometry. The ADVIA 120 (Bayer) is a new system that facilitates more accurate measurement of platelet volume and in addition provides an approximate measure of the mean refractive index (RI) of the platelets reported as mean platelet component (MPC) concentration. We were interested to determine whether changes in MPC might reflect changes in platelet activation status. To investigate this, the platelet CD62P expression, determined by flow cytometry, and change in MPC, measured on the ADVIA 120 system, was first examined in vitro after stimulation of EDTA anticoagulated whole blood with submaximal concentrations of bovine thrombin in the presence or absence of the thromboxane synthase inhibitor, Ridogrel. Thrombin produced a dose-dependent increase in platelet CD62P expression and a decrease in MPC that could be inhibited by Ridogrel at physiological concentrations. In the second set of experiments, blood from 20 normal controls was collected into both EDTA and sodium citrate (SC) anticoagulants. Within 30 min of venesection and again at 3 h post-venesection after storage at room temperature, the platelet MPC and CD62P expression were determined. Platelets in all samples with both anticoagulants showed very low levels of CD62P expression when first analysed. At 3 h there was a small increase in CD62P expression on platelets in whole blood anticoagulated with SC, but a significant (P < 0.001) increase was observed on platelets anti-coagulated with EDTA. A negative correlation was found between the change in MPC of the platelets and the increase in the mean fluorescence intensity (MFI) (r = −0.69, P < 0.001, n = 20) and the percentage (r = −0.72, P < 0.001, n = 20) of CD62P positive platelets at 3 h in blood anticoagulated with EDTA. We conclude that a reduction in MPC as measured by the ADVIA 120 may be used to detect anticoagulant induced, as well as thrombin stimulated, in vitro platelet activation in blood anticoagulated with EDTA. Further, we conclude that platelet activation is negligible for up to 3 h in sodium citrate anticoagulated whole blood. Cytometry (Comm. Clin. Cytometry) 38:250–255, 1999. © 1999 Wiley-Liss, Inc.

Use of mean platelet component to measure platelet activation on the ADVIA 120 haematology system.

Platelet activation results in changes in a number of cell surface molecules including an increase in P-Selectin (CD62P) that may be rapidly and conveniently measured by immunofluorescent flow cytometry. The ADVIA 120 (Bayer) is a new system that facilitates more accurate measurement of platelet volume and in addition provides an approximate measure of the mean refractive index (RI) of the platelets reported as mean platelet component (MPC) concentration. We were interested to determine whether changes in MPC might reflect changes in platelet activation status. To investigate this, the platelet CD62P expression, determined by flow cytometry, and change in MPC, measured on the ADVIA 120 system, was first examined in vitro after stimulation of EDTA anticoagulated whole blood with submaximal concentrations of bovine thrombin in the presence or absence of the thromboxane synthase inhibitor, Ridogrel. Thrombin produced a dose-dependent increase in platelet CD62P expression and a decrease in MPC that could be inhibited by Ridogrel at physiological concentrations. In the second set of experiments, blood from 20 normal controls was collected into both EDTA and sodium citrate (SC) anticoagulants. Within 30 min of venesection and again at 3 h post-venesection after storage at room temperature, the platelet MPC and CD62P expression were determined. Platelets in all samples with both anticoagulants showed very low levels of CD62P expression when first analysed. At 3 h there was a small increase in CD62P expression on platelets in whole blood anticoagulated with SC, but a significant (P < 0.001) increase was observed on platelets anti-coagulated with EDTA. A negative correlation was found between the change in MPC of the platelets and the increase in the mean fluorescence intensity (MFI) (r = -0.69, P < 0.001, n = 20) and the percentage (r = -0.72, P < 0.001, n = 20) of CD62P positive platelets at 3 h in blood anticoagulated with EDTA. We conclude that a reduction in MPC as measured by the ADVIA 120 may be used to detect anticoagulant induced, as well as thrombin stimulated, in vitro platelet activation in blood anticoagulated with EDTA. Further, we conclude that platelet activation is negligible for up to 3 h in sodium citrate anticoagulated whole blood.

Opto-thermal properties of fibres: 5. Structure variations in nylon 66 fibres due to different thermal conditions

Nylon 66 fibres were annealed at a temperature of 90–180°C for 6 h and quenched in coarse ice. Refractive indices and birefringence were measured interferometrically. Three independent techniques have been used to study the optical anisotropy in these fibres. The first technique is to study the geometrical parameters from the diffraction pattern using a He–Ne laser beam, the second is the application of two-beam interferometry to determine the mean refractive indices and double refraction of annealed samples. The third, acoustic method has been used for measuring the density and the mechanical loss factor of these fibres. The optical results data were used to calculate the mean polarizability per unit volume, the isotropic refractive indices, and optical orientation. The value of (Δ α/3 α 0) which depends upon the molecular structure of the polymer remains constant and is in agreement with previous published data. Behaviour of optical properties at different annealing conditions is discussed. The density results were used to calculate the degree of crystallinity of nylon 66 fibres. In addition, the resulting data were used to calculate the mean density fluctuation at different annealing conditions. The results obtained clarify the new reorientation and change occurring due to annealing at different conditions. The changes in the refractive index profile of annealed and quenched nylon 66 fibres at different conditions are given. Microinterferograms and curves are given for illustration.

Molar mass and size of Norwegian aquatic NOM by light scattering

Natural organic material (NOM), isolated from eight Norwegian surface waters using reverse osmosis and low pressure evaporation, was characterized by high performance size exclusion chromatography (HPSEC) coupled with multi-angle laser light scattering (MALLS) and refractive index (RI) detection. This technique was used to measure the molar mass and radius of the natural organic matter in solution. Values reported include number- and weight-averaged molar masses (M n, M w; 1702 to 88 310 g mol −1), root mean square (r.m.s.) radii (R n, R w; 25 to 156 nm), polydispersities (1.074–1.769), and refractive index increments ( d n d c ; 0.101 to 0.176 mL g −1) for all the samples. High standard deviations in the data did not allow the detection of significant differences in the molecular sizes of reverse osmosis vs. low pressure evaporation isolated samples. The high standard deviations are believed to be the result of using high sample concentrations with the HPSEC separation.

Opto-mechanical properties of fibres. Part 1. Optical properties and orientation of drawn polyethylene fibres

Changes in the structure of different drawn polyethylene (PE) fibres are studied by the Becke' line method and interferometrically. The Becke' line method is used to study the changes in the optical properties of the skin layer of PE undrawn fibres. A Pluta polarizing interference microscope is used to determine the mean refractive indices and mean birefringence of the drawn fibres. Some structural parameters, such as optical orientation function, electric polarizability difference and isotropic polarizability (Δα/3α0), are determined. This last parameter is found to be constant and depends only on the fibre structure. The number of molecules per unit volume and the distribution of segments at an angle with respect to the draw ratio are also determined. The generalized Lorentz–Lorenz equation given by de Vries is used to determine PE fibre structural parameters. A comparison between the experimental and those obtained using the Lorentz–Lorenz equation is given. A refractive index profile can assist fibre characterization. An empirical formula is suggested to correlate the changes in A, Δn, fθ and θ with the draw ratio, and its constants are determined. Microinterferograms and curves are given for illustration. © 1999 Society of Chemical Industry

Heterogeneous nucleation of calcium phosphate salts at a solid/liquid interface examined by scanning angle reflectometry

Mineralization of calcium phosphate salts at a solid/liquid silica interface was examined by means of scanning angle reflectometry (SAR). A critical supersaturation of 7.60±0.15 mM was found to be the lowest calcium phosphate concentration at pH 6.85 at which the reflectivity at the Brewster angle started to vary. The analyses of the signals by mean of the homogeneous isotropic layer model led to layer thicknesses of about 3.5 μm also characterized by very low mean refractive index increments. These observations were completed by complementary experiments. Scanning and transmission electron microscopy led to similar layer thicknesses with crystallites dispersed in the whole layer confirming thus SAR results. X-ray analyses showed a presence of brushite (DCPD) at the silica interface. A pH of 5.44 was estimated for the acidic silica interface for which DCPD is nucleated after addition of 7.60±0.15 mM calcium and phosphate. However, at this pH value, the solution is largely supersaturated with respect to hydroxyapatite (HAP theoretical saturating concentration: 1.37 mM). A faster growth of DCPD crystals compared to HAP crystals is thus assumed to explain our observations.

Optothermal properties of fibers: 12-Interferometric investigation for thermally treated viscose fibers

The present article studies the structure of annealed viscose fibers interferometrically at a constant temperature of 100 ± 1°C at different times. The Pluta polarizing interference microscope has been used for determining the mean refractive indices and mean birefringence. The results were used to calculate the optical orientation function and the angle of orientation. The value (Δα/3α0), which depends on the molecular structure of the polymer, remains constant. Relationships between the mean refractive indices, birefringence, isotopic refgractive index, and polarizabilities per unit volume with different times were given for these fibers. The samples were subjected to X-ray diffraction to clarify the variation of crystallinity with the annealing conditions. Differential thermal analysis measurements were used to determine the glass transition temperature of viscose fiber. Measurements of the volume swelling parameter of the viscose fibers with different liquids were given. Also, determinations of Cauchy's constants, dispersive power, and dielectric constant at infinity were carried out. Illustrations are given using graphs and microinterferograms. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 361–369, 1999

Changes in Opto-Thermal Properties of PET Fibres during Annealing

The changes in refractive indices and the birefringence of polyester (Egyptian PET) fibres with different annealing conditions were studied by interferometry. The polarizing interference microscope was used to determine the mean refractive indices and mean birefringence of these fibres. An acoustic method has been used to measure densities. The results are used to calculate structural parameters such as the form birefringence, virtual refractive index, harmonic mean polarizability of the dielectric, the number of molecules per unit volume, and the specific refractivity of the isotropic dielectric. Also, the number of monomer units per unit volume and the refractive indices of the fully oriented fibre, when using monochromatic light vibrating parallel and perpendicular to the fibre axis, were calculated and found to be 1.803 and 1.562. The effect of the annealing conditions on the refractive index was studied. The generalized Lorentz-Lorenz equation given by de Vries was used to determine PET fibre structural parameters. Comparisons between the Hermans optical orientation function formula and the corrected formula by de Vries are given.

Changes in Opto-Thermal Properties of PET Fibres during Annealing

The changes in refractive indices and the birefringence of polyester (Egyptian PET) fibres with different annealing conditions were studied by interferometry. The polarizing interference microscope was used to determine the mean refractive indices and mean birefringence of these fibres. An acoustic method has been used to measure densities. The results are used to calculate structural parameters such as the form birefringence, virtual refractive index, harmonic mean polarizability of the dielectric, the number of molecules per unit volume, and the specific refractivity of the isotropic dielectric. Also, the number of monomer units per unit volume and the refractive indices of the fully oriented fibre, when using monochromatic light vibrating parallel and perpendicular to the fibre axis, were calculated and found to be 1.803 and 1.562. The effect of the annealing conditions on the refractive index was studied. The generalized Lorentz-Lorenz equation given by de Vries was used to determine PET fibre structural parameters. Comparisons between the Hermans optical orientation function formula and the corrected formula by de Vries are given.

Study of the behavior of biological molecules in a thin gap by refractive index and force measurements with an automatic surface force apparatus

The automation of the mica surface displacement of a surface force apparatus (SFA) increases the accuracy of the intermolecular force measurements that is obtained without the presence of the experimenter. The automatic device cancels any thermal drift and the stability of the mica surfaces is optimum. The distance between the mica surfaces is measured by Tolansky multiple-beam interforometry (FECO method) which offers a sensitivity of 0.1 nm in the direction perpendicular to the plane of contact area. The mean refractive index of the medium between the mica plates is computed from simultaneous measurements of the wavelengths of two successive fringes of equal chromatic order (FECO). A conversion of an isotropic molecule to another anisotropic molecules can be identified from the variations of the refractive index. In good conditions, we can compute the local concentration of the molecules in the gap of the device, and estimate the Young's modulus of a protein.

Influence of creep on optical properties of polypropylene fibers

The change in some optical properties with the creep extension is measured for polypropylene fibers at several constant applied loads. Multiple-beam Fizeau fringes in transmission are used to determine the mean refractive indices and the mean birefringence of these fibers at different values of creep extensions. Also, the effect of creep extension on the birefringence profile of the fiber is studied. The creep-extension dependence of these optical properties for polypropylene fibers is demonstrated using a stress-strain device connected to a wedge interferometer where the fiber is subjected to a constant load. The results show that under constant load the fiber will extend with time at a rate which decreases as time increases. An empirical formula is suggested to represent the variation of creep extension (%) of polypropylene fibers with time in the time interval of 0-55 min and the constants of this formula are determined. Microinterferograms are given for illustration.

On the birefringence of magnetoelectric BiFeO3

The birefringence dispersion of a ferroelastic single domain of magnetoelectric BiFeO3 crystal has been measured at room temperature (24°C) in the rhombohedral phase. A thin (11μm) (110)cubic cut was used although it was not a principal cut. The optical axis (and spontaneous polarization) formed an angle of 35° with the normal to the cut. Due to anomalous interference colors, the right order was deduced with the help of conoscopy. The birefringence of this cut shows normal dispersion and its value is very large (dn′ = 0.13 at λ = 550 nm to 0.08 at λ = 850 nm). The principal birefringence (dn = 0.34 at A = 550 nm) has been evaluated with the help of the computed (Gladstone-Dale relationship) mean refractive index ([nbar] = 2.62). From dn′ (T), (8K < T < 820 K) the Néel temperature has been found for the first time optically, TN =653K (380°C), and a critical exponent has tentatively been derived near TN .

Opto-Thermal Properties of Fibres. Part 2: Investigation of Optical Parameter Changes in Annealed and Quenched Nylon 6-6

The changes in refractive indices and birefringence of nylon 6-6 fibres with different annealing conditions were” studied by interferometry. The polarizing interference microscope was used to determine the mean refractive indices and mean birefringence of these fibres. Also, an acoustic method has been used to measure densities. The results are used to calculate some structural parameters such as the form birefringence, virtual refractive index, harmonic mean polarisability of the dielectric, and the specific refractivity of the isotropic dielectric. Also, the number of monomer units per unit volume and the refractive indices of fully oriented fibre, when using monochromatic light vibrating parallel and perpendicular to the fibre axis, were calculated and found to be 1.5543 and 1.4723. The generalized Lorentz-Lorenz equation given by de Vries was used to determine nylon 6-6 fibre structural parameters. Comparisons between Herman's optical orientation function formula and the corrected formula by de Vries are given.

Opto-Thermal Properties of Fibres. Part 2: Investigation of Optical Parameter Changes in Annealed and Quenched Nylon 6-6

The changes in refractive indices and birefringence of nylon 6-6 fibres with different annealing conditions were” studied by interferometry. The polarizing interference microscope was used to determine the mean refractive indices and mean birefringence of these fibres. Also, an acoustic method has been used to measure densities. The results are used to calculate some structural parameters such as the form birefringence, virtual refractive index, harmonic mean polarisability of the dielectric, and the specific refractivity of the isotropic dielectric. Also, the number of monomer units per unit volume and the refractive indices of fully oriented fibre, when using monochromatic light vibrating parallel and perpendicular to the fibre axis, were calculated and found to be 1.5543 and 1.4723. The generalized Lorentz-Lorenz equation given by de Vries was used to determine nylon 6-6 fibre structural parameters. Comparisons between Herman's optical orientation function formula and the corrected formula by de Vries are given.

Optothermal properties of fibers. VII. Optical investigation of annealed nylon‐6 fibers

The influence of annealing on the birefringence of nylon-6 fibers was examined. These fibers were found to show considerable optical anisotropy. Three independent techniques were used to study the optical anisotropy in these fibers. The first technique to determine the diameter of the fiber from the diffraction pattern was using a He—Ne laser beam. The second technique was the application of the Becke-line technique to study the effect of annealing on the skin layer of these fibers at different temperatures for a constant time of 5 h. The third is the application of a double-refracting interference microscope (the Pluta polarizing interference microscope). The double-beam technique is considered as the most suitable technique for determining the mean refractive indices and the double refraction of the annealed samples at different temperatures. (155 and 175°C and at two constant times 7 and 9 h). Microinterferograms and curves are given for illustration. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:1293–1306, 1997

Optothermal properties of fibers. VII. Optical investigation of annealed nylon-6 fibers

The influence of annealing on the birefringence of nylon-6 fibers was examined. These fibers were found to show considerable optical anisotropy. Three independent techniques were used to study the optical anisotropy in these fibers. The first technique to determine the diameter of the fiber from the diffraction pattern was using a He—Ne laser beam. The second technique was the application of the Becke-line technique to study the effect of annealing on the skin layer of these fibers at different temperatures for a constant time of 5 h. The third is the application of a double-refracting interference microscope (the Pluta polarizing interference microscope). The double-beam technique is considered as the most suitable technique for determining the mean refractive indices and the double refraction of the annealed samples at different temperatures. (155 and 175°C and at two constant times 7 and 9 h). Microinterferograms and curves are given for illustration. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:1293–1306, 1997

Anisotropic Optical Properties of Nylon 6-6 Fibres as a Function of Annealing and Quenching Processes

Changes in the structure of nylon 6-6 fibres after annealing and quenching in coarse grained ice at 160°C were studied interferometrically. The Pluta polarising interference microscope has been used to determine the mean refractive indices and mean birefringence of these fibres. The optical orientation function and the molecular structure of the annealed and quenched nylon 6-6 fibres were calculated. The density and the mechanical loss factor of the annealed and quenched fibres were measured by a system based on vibrating strings. The density results were used to calculate the degree of crystallinity. Relationships between the mean refractive indices, birefringence, isotropic refractive index and polarisabilities per unit volume at various times are given for these fibres. The behaviour of fibre density and the mechanical loss factor under different annealing and quenching conditions were discussed with different optical parameters. The results obtained clarify the effect of annealing and quenching conditions on the orientation function, orientation angle and other optical and mechanical parameters. The effect of the annealing conditions on the refractive index profile was studied. Illustrations are given using graphs and microinterferograms.

Sub‐Fresnel‐scale vertical resolution in atmospheric profiles from radio occultation

We have investigated the vertical resolution that can be achieved in atmospheric profiles retrieved from radio occultation measurements. The results are based on forward simulations of radio wave propagation through model atmospheres using the multiple phase‐screen method. We find that profiles retrieved through Abel inversion, the standard algorithm derived from geometrical optics, have a vertical resolution that is diffraction‐limited, as expected. To overcome this limitation, we have developed an advanced retrieval algorithm, which is based on scalar diffraction theory and properly accounts for diffraction effects. We demonstrate that the method is capable of retrieving accurate refractivity profiles at sub‐Fresnel‐scale resolution for Mars‐ and Earth‐like atmospheres. It also provides a natural means for deciphering multipath propagation effects. The method seems capable of enhancing resolution by a factor of 10 beyond the diffraction limit. In one simulation involving an Earth‐like model atmosphere the algorithm successfully retrieved a profile in which the refractive index changed by 10−5 over a vertical scale of 250 m. The maximum vertical gradient of refractive index within this small‐scale feature was about 0.8×10−7 m−1. For comparison, critical refraction occurs for a gradient of about 1.6×10−7 m−1. The feature was embedded in a smooth refractive index profile at the level where the pressure and mean refractive index were 42 kPa and 1.00013, respectively. Total refractive bending for a ray that grazed this level was 0.01–0.02 rad.