Gender differences in choice reaction time: evidence for differential strategies

This study considered the hypothesis that on some tasks men and women might employ different information processing strategies. Twelve male and 12 female participants performed a 2- and 4-choice, compatible and incompatible, choice reaction time task that required a verbal response to a spatial location target stimulus. Results demonstrated a near-significant overall reaction time advantage for male participants. Moreover, males and females showed a differential pattern of reaction time as a function of stimulus location. Specifically, in the 4-choice-compatible condition, females exhibited a linear increase in reaction time as a function of the left-right dimension; males, on the other hand, showed a two-component, step-like increase. It was suggested that this gender difference in reaction time performance may reflect differences in processing strategy. Specifically, it was argued that in the present task females may have employed a serial, left-to-right, processing strategy, and males a binary, split-half (dichotomizing) strategy.     

Conductometric detection of anions of weak acids in chemically suppressed ion chromatography: critical point concentrations

Previously we demonstrated that the conductometric determination of anions of weak acids in chemically suppressed ion chromatography could be enhanced, by conversion of the acid to a conjugate salt, if the anion was present above what we termed the critical point concentration (CPC). In this paper we have developed a simple theoretical model for the calculation of CPCs for weak acid/conjugate salt pairs. The CPC was found to be dependent on the acid ionization constant K(a) and the molar ionic conductivities (MICs) of the ions present. For monovalent anions with a MIC in the common range 25-75 S cm(2) mol(-)(1), with sodium or potassium as cations, the CPCs could be estimated from the expression pC ≈ pK(a) - 1, where pC = -log CPC. For formate, benzoate, and acetate, excellent agreement was found between the calculated and experimental CPCs, with a mean deviation of 0.05 mM. For fluoride, the calculated and experimental CPCs were 7.4 and 9.2 mM, respectively. Experimental CPCs could not be determined for other anions as their calculated CPCs were below the detection limits of the IC system. The simple theoretical model could also be used to estimate the expected conductivity enhancement for the conversion of weak acid to a particular conjugate salt. The effects of detector linearity and dispersion in the IC system on the use of CPCs are also discussed.     

Integrated electro-optic lens/scanner in a LiTaO3 single crystal

We report what we believe to be the first stand-alone integrated electro-optic lens and scanner fabricated on a single crystal of Z-cut LiTaO(3). The independently controlled lens and scanner components consist of lithographically defined domain-inverted regions extending through the thickness of the crystal. A lens power of 0.233 cm(-1) kV(-1) and a deflection angle of 12.68 mrad kV(-1) were observed at the output of the device.     

Encoding amplitude information onto phase-only filters

We report a new, to our knowledge, technique for encoding amplitude information onto a phase-only filter with a single liquid-crystal spatial light modulator. In our approach we spatially modulate the phase that is encoded onto the filter and, consequently, spatially modify the diffraction efficiency of the filter. Light that is not diffracted into the first order is sent into the zero order, effectively allowing for amplitude modulation of either the first-order or the zero-order diffracted light. This technique has several applications in both optical pattern recognition and image processing, including amplitude modulation and inverse filters. Experimental results are included for the new technique.     

Light backscattering polarization patterns from turbid media: theory and experiment

We present both experimental measurements and Monte-Carlo-based simulations of the diffusely backscattered intensity patterns that arise from illuminating a turbid medium with a polarized laser beam. It is rigorously shown that, because of axial symmetry of the system, only seven elements of the effective backscattering Mueller matrix are independent. A new numerical method that allows simultaneous calculation of all 16 elements of the two-dimensional Mueller matrix is used. To validate our method we compared calculations to measurements from a turbid medium that consisted of polystyrene spheres of different sizes and concentrations in deionized water. The experimental and numerical results are in excellent agreement.     

Spatiotemporal phase unwrapping for the measurement of discontinuous objects in dynamic fringe-projection phase-shifting profilometry

A spatiotemporal phase-unwrapping method is presented that combines the dynamic fringe-projection method and the phase-shifting technique and extends the phase-unwrapping method, which measures two phase maps at different sensitivities. The most important feature of the method is that it makes possible the automatic three-dimensional shape measurement of discontinuous objects with large dynamic range limits and high precision because the effective wavelength of the fringe-projection profilometry can be continuously varied over several orders of magnitude by rotation of the projection grating in its own plane. Only one grating and several steps of rotating the grating are required; therefore the method is inherently simple, fast, and robust. In the experiment, choosing the rotation angle was crucial for optimizing the measurement speed and the measurement accuracy. A criterion is presented for the choice of the minimum number of rotational steps for a given accuracy. The experimental results demonstrate the validity of the proposed method.