Peak Retardation Research Articles

Calibration for phase retardation of photoelastic modulator based on compound Bessel function

The photoelastic modulator (PEM) is an optical modulation device which is widely used in optical detections. In this paper, we propose a high-precision and large-scale method for calibrating the peak retardations of PEM based on compound Bessel function. By applying compound Bessel function instead of the single Bessel function, the uncertainty of peak retardation calibration result decreases more than two times and the calibration scale expands nearly two times. Further, the second harmonic component is substituted for the DC component to reduce the random errors. In the experiment, a PEM is calibrated and the calibration result obtained for peak retardation is linear to the setting value in scale 0.15–2.5 rad. A dead zone appears in region 0 to 0.15 rad with value 0.233 rad. The experiment demonstrates that the relative uncertainty of peak retardation decreases from 2.5 % to less than 1 %.

Measurement of Circular Dichroism Spectra without Control of a Phase Modulator using Retardation Domain Analysis

This study investigated the measurement of circular dichroism (CD) spectra without controlling a phase modulator. In a conventional CD system, the peak retardation of the phase modulator must remain constant over the observed wavelength range. Thus, the phase modulator must be controlled to maintain an appropriate modulation degree at an observed wavelength. In contrast, CD obtained using retardation domain analysis is not affected by peak retardation. Consequently, CD spectra can be measured without control of the phase modulator, which was experimentally demonstrated in this study. Additionally, linear dichroism spectra were obtained using retardation domain analysis.

Method for simultaneously calibrating peak retardation and static retardation of a photoelastic modulator.

A method for simultaneously calibrating the peak retardation and static retardation of a photoelastic modulator (PEM) is proposed. By optimizing the polarization modulation system, the normalized fundamental frequency components of the modulation signals are obtained to calculate the peak retardation and static retardation of the PEM. The calibration result is immune to fluctuations of the incident light intensity and can be used to correct the deviation of the photoelastic modulation detection results. In our experiments, the average deviation between measured peak retardations and corresponding set values is 0.0339 rad. The standard deviation between the measured static retardations and the average measured value is 0.0003 rad. The calibration method has a high sensitivity, since the large gradient of the first-order Bessel function when the peak retardation is less than 1 rad. The experimental results are consistent with the theoretical analysis.

Calibration of photoelastic modulator using direct current component

A method of calibrating the photoelastic modulator (PEM) using direct current component is proposed. The laser beam passes through a polarizer, the PEM to be calibrated and is then split into two sub-beams by a Wollaston prism. The two sub-beams are then detected by two detectors. The small peak retardation is independent of the fluctuation of the initial intensity. The calibration setup is compact. In experiments, a PEM was calibrated and the calibration error was less than 0.008rad when the peak retardation changed in the range of 0.1λ–0.5λ.

Simultaneous measurement of small birefringence magnitude and direction in real time

A method to simultaneously measure the small birefringence magnitude and direction in real time is proposed. The laser light passes through a circular polarizer and the sample successively. Then the beam is split into two sub-beams by a beam splitter. Each sub beam is then split and analyzed by a Wollaston prism. Four intensities are simultaneously detected by four detectors to resolve the birefringence magnitude and direction in real time. The measurement result is immune to fluctuation of the initial intensity. In experiments, a photoelastic modulator with small peak retardation was measured at different birefringence magnitudes and directions. The maximum deviation of the birefringence magnitude is less than 1.68nm, and the standard deviation of the birefringence direction is less than 0.47°. The validity of the method is verified.

Adsorptive removal of aqueous fluoride by liner minerals from SPL-landfill leachate during the seepage process

The breakthrough curve (BTC) of F− through a lining layer composed of kaolinite and montmorillonite was investigated in a one-dimensional seepage system as functions of the initial F− concentration, liner thickness, seepage velocity and presence of a co-solute. The removal of F− from the seepage system was much greater than that estimated from the batch adsorption result, probably due to the high liner mass-leachate volume ratio. By lowering the F− feed concentration from 30 to 15mg/L, the peak retardation (μ′1) was enhanced by 30–60%, which was consistent with the nonlinear F− adsorption (N<1) for the given materials. From a column with 1.5-times thicker liner (6cm), more than 80% of the peak concentration was reduced with both kaolinite and montmorillonite compared to the thinner layer (4cm). However, when the seepage velocity was doubled from 3.4×10−3 to 6.8×10−4cm/s, the peak concentration was increased by 20–30% and an early peak arrival was detected. The presence of 0.035mM [Fe(CN)6]4− showed no significant impact, as shown in the batch adsorption system. In conclusion, the thickness of the liner and seepage rate through the liner layer should be primary factors in determining the efficacy of F− removal from SPL-induced leachate.

Calibration method for a photoelastic modulator with a peak retardation of less than a half-wavelength

A new calibration method for a photoelastic modulator is proposed. The calibration includes a coarse calibration and a fine calibration. In the coarse calibration, the peak retardation of the photoelastic modulator is set near 1.841 rad. In the fine calibration, the value of the zeroth Bessel function is obtained. The zeroth Bessel function is approximated as a linear equation to directly calculate the peak retardation. In experiments, the usefulness of the calibration method is verified and the calibration error is less than 0.014 rad. The calibration is immune to the intensity fluctuation of the light source and independent of the circuit parameters. The method specially suits the calibration of a photoelastic modulator with a peak retardation of less than a half-wavelength.

Rheo-optics of Equilibrium Polymer Solutions: Wormlike Micelles in Elongational Flow in a Microfluidic Cross-Slot

The rheo-optical analysis of polymer solutions and melts is a critical tool in elucidating their molecular response to flow fields. We therefore evaluate the measurement of flow-induced birefringence (orientation) under extension in microfluidic cross-slots, whose flow kinematics was examined by microparticle image velocimetry. The effects of planar extension on the (non)linear viscoelasticity of wormlike micellar surfactant solutions (comprising either cetyltrimethylammonium bromide or cetylpyridinium chloride in aqueous sodium salicylate) were measured. The effect of wall shear was found to be negligible compared to extension. The birefringence is linear (indicating the validity of the stress−optical rule) for very small extensional Weissenberg numbers, as expected. This rule fails, however, when a sharp birefringence band appears at modest Weissenberg number (indicating the alignment of wormlike micelles along the outflow direction). Experiments that measure average birefringence may misidentify the point of failure of the stress−optical rule. These bands also scatter light and appear in transmittance images, yet with distinctive features. At higher flow rates, the birefringent band broadens after the peak retardation saturates, but the transmittance band remains narrow and eventually the flow becomes asymmetric. This asymmetric transition is elasticity-induced, and no shear banding is observed by particle velocimetry: the velocity profiles remain linear, while the flow becomes asymmetric. These phenomena are common to both fluids studied, but the stress−optical coefficient and the Weissenberg numbers at saturated birefringence differ quantitatively, possibly due to differences in micellar length and scission kinetics, as determined from linear viscoelastic measurements.

Search for serum protein-binding disaccharides and disaccharide-binding serum proteins by affinity capillary electrophoresis.

The potential use of affinity capillary electrophoresis in a microscale search for mutually interacting substances in biological fluid is demonstrated. Some disaccharides, especially gentiobiose (Gen), derivatized with 1-phenyl-3-methyl-5-pyrazolone, caused peak retardation when electrophoresed in a neutral running buffer, containing human serum. Gen, the most significantly retarded disaccharide, was converted to its negatively charged bis-mercaptoethanesulfonate derivative (MerESGen), and a serum sample was analyzed in a neutral buffer containing the derivatized disaccharide. Two peaks, belonging to the beta-globulin fraction, were found to be remarkably retarded in the buffer containing MerES-Gen in a concentration-dependent way. These findings prove an interaction between disaccharides and serum proteins.

Scanning laser polarimetry of the normal human retinal nerve fiber layer: a quantitative analysis

PURPOSE: To provide a quantitative comparison of retardation values obtained with the scanning laser polarimeter (Nerve Fiber Layer Analyzer; Laser Dignostic Technologies, San Diego, California) in normal subjects, with the known histologic properties of the human retinal nerve fiber layer. METHODS: Scanning laser polarimetry was performed on 48 normal subjects. The retardation values obtained from each eye were processed to remove reflections from the optic nerve head vasculature and to derive peripapillary polar retardation profiles. The location of the maximum and minimum retardation values superior and inferior to the disk was determined. Retardation values were also determined along lines running radially from the center of the optic disk to through the points of maximal retardation. RESULTS: Retardation values were greater in the superior and inferior quadrants of the peripapillary retinal nerve fiber layer compared with the nasal and temporal quadrants. Superiorly, peak retardation values were nasal to the vertical meridian by 22.9 degrees (SD, 17.5) in right eyes and by 15.7 degrees (SD, 17.7) in left eyes. Inferiorly, the peak showed a closer correspondence with the vertical meridian, lying nasal to this by 0.8 degrees (SD, 14.9) in right eyes and temporal to this by 2.8 degrees (SD, 15.4) in left eyes. Radial analysis showed that the peak retardation occurred approximately (0.5 to 0.7 disk diameters from the optic disk margin) at the superior and inferior aspect of the disk. The degree of modulation of retardation around the optic disk was less than would be expected from the variation in peripapillary nerve fiber layer thickness seen histologically. CONCLUSION: The location of the peak retardation values shows reasonable agreement with the angular location of the peak values of nerve fiber layer thickness published for humans. By contrast, the modulation of retardation values around the disk and the change with eccentricity from the optic disk center differ from the anatomic data. The Nerve Fiber Layer Analyzer appears to measure a correlate of nerve fiber layer thickness, but it is important that any discrepancies between the retardation and anatomic data are recognized in the clinical interpretation of polarimetric data.

The Grimsel Migration Experiment: field injection–withdrawal experiments in fractured rock with sorbing tracers

In the framework of the Migration Experiment at the Grimsel Test Site, Switzerland, breakthrough experiments with a conservative tracer, uranine, and sorbing cationic γ-emitting radionuclides ( 22,24 Na + , 85 Sr 2+ , 86 Rb + , and 137 Cs + ) were carried out to test models of radionuclide migration in the field. An array of bore holes drilled from an experimental drift penetrated a transmissive, water-saturated shear zone in a granodiorite. The shear zone consists of a set of fractures filled with a fine-grained porous fault gouge. A two bore hole injection-withdrawal (`dipole') flow field was superimposed on the natural hydraulic gradient and two different linear flow distances, 1.7 and 4.9 m, were studied in detail. The concentrations of the radionuclides were, in general, much smaller than the natural background levels of the corresponding stable isotopes of Na, Sr, Rb, and Cs, in the groundwater of the shear zone. In-line tracer detection techniques included down-hole point fluorescence measurement and NaI scintillation counting of γ-emitters in the withdrawal flow line. Pulse-stimulus tracer injections resulted in monomodal breakthrough curves and recovery curves. The reduction of the maximum (peak) radionuclide activity (relative to the injected activity), peak retardation, and retardation of the time of 50% recovery were compared to those of uranine. A selectivity sequence of relative affinity of the studied cations for an exchange site was found to be Na (<Ca)<Sr<Rb<Cs. In the shorter flow field, the radionuclides exhibited little peak-height reduction relative to uranine and little or no retardation. In the longer flow field, Sr and Cs showed a considerable peak-height reduction and a significant retardation relative to uranine and Na. Increasing the flow distance affected the retardation of the radionuclides. The results were compared with both pre- and post-experiment model simulations and earlier model predictions.

Quantitative studies on the polarization optical properties of living cells II. The role of microtubules in birefringence of the spindle of the sea urchin egg.

Birefringence of the mitotic apparatus (MA) and its change during mitosis in sea urchin eggs were quantitatively determined using the birefringence detection apparatus reported in the preceding paper (Hiramoto el al., 1981, J. Cell Biol. 89:115-120). The birefringence and the form of the MA are represented by five parameters: peak retardation (delta p), through retardation (delta t), interpolar distance (D1), the distance (D2) between chromosome groups moving toward poles, and the distance (D3) between two retardation peaks. Distributions of birefringence retardation and the coefficient of birefringence in the spindle were quantitatively determined in MAs isolated during metaphase and anaphase. The distribution of microtubules (MTs) contained in the spindle is attributable to the form birefringence caused by regularly arranged MTs. The distribution coincided fairly well with the distribution of MTs in isolated MAs determined by electron microscopy. Under the same assumption, the distribution of MTS in the spindle in living cells during mitosis was determined. The results show that the distribution of MTs and the total amount of polymerized tubulin (MTs) in the spindle change during mitosis, suggesting the assembly and disassembly of MTs as well as the dislocation of MTs during mitosis.

Sarcomere reorganization in mite muscle

The number of sarcomeres in a given muscle of the mite Tarsonemus randsi was constant in both larval and adult stages, with the exception of the two medial dorsal metapodosomal muscles in males. These muscles have three sarcomeres in larvae and one sarcomere in adults. This change in sarcomere number within a muscle was observed in the living animal by polarized light microscopy using parthenogenetically derived male larvae. Initially the transforming muscles shortened slowly (hours) and the appearance of the sarcomeres was comparable to that seen during normal contraction. With continued shortening there was apposition of adjacent A bands and disappearance of clearly visible Z lines, but no loss of birefringence. Over the next 12 hr there was further shortening of the muscle and loss of birefringence. This was apparent as shortening of the three apposed A regions to the length of a single A band with a small increase in muscle width and no increase in the peak retardation of the birefringent region. The observations are discussed in terms of differential loss of the A filaments of the two terminal sarcomeres.