Light Reflection Technique Research Articles

Intrasaccadic target steps during the deceleration of primary saccades affect the latency of corrective saccades.

This study investigates how visually guided saccades and subsequent corrective saccades are affected by a secondary target step occurring at different times during the primary saccade. Eye movements of human subjects were measured by means of a differential infrared light reflection technique while the subjects performed visually guided saccades to a laser spot in darkness. The target was stepped backward or onward during the targeting saccade. While the intrasaccadic target step did not influence gain, peak velocity or skewness of the primary saccade, it had a significant effect on the subsequent corrective saccade when the secondary target step occurred during the deceleration phase of the primary saccade: the latency of the corrective saccade was significantly increased compared with the one performed under the single-step control condition. This increase also occurred when single target steps were presented randomly intermixed with backward and onward double target steps and even between selected sub-samples of saccades with identical postsaccadic visual error. If the target step occurred early during the primary saccade, the latency of the corrective saccade was not changed. This indicates that visual information sampled during the deceleration phase of a saccade can lead to a cancellation of the normal trigger mode of corrective saccades.

Iron Passivity in Borate Buffer: Formation of a Deposit Layer and Its Influence on the Semiconducting Properties

The formation, growth, and dissolution of the passive film on iron in neutral and alkaline solutions was investigated using a light reflectance technique. It was found that depending on the hydrodynamic conditions the formation of a hydroxide layer can take place during passivation. The strong influence of the hydrodynamic conditions can explain many contradictory results in the literature concerning the presence of a hydroxide layer on the protecting oxide film. Furthermore, the hydroxide layer affects capacitance and photocurrent measurements which are frequently used to obtain information about the semiconducting properties of the passive film on iron. In photoelectrochemical experiments the incoming photon flux is attenuated by the hydroxide layer which results in a decrease of photocurrent intensity. In ac‐impedance measurements the potential dependence of the capacitance is qualitatively not affected, but a significantly increased frequency dispersion of the results is observed.

Comparison of the Semiconductive Properties of Sputter‐Deposited Iron Oxides with the Passive Film on Iron

The semiconducting properties of sputtered magnetite and oxidized magnetite layers with different Fe(II) contents were compared with the passive film on iron. Electrochemical impedance spectroscopy and photoelectrochemical experiments were carried out in borate buffer, pH 8.4. An evaluation of the impedance data according to the Mott‐Schottky concept showed that the capacitance of all films is linked with their doping concentrations rather than their thicknesses and that the doping species of the passive film on iron is Fe(II). For the passive film a potential‐dependent doping concentration was found. Photoelectrochemical investigation of the passive film and the sputtered oxide layers showed that for low doping concentrations, the photocurrent increases with doping, whereas for high doping concentrations, an increase in doping leads to a decrease of the photocurrent. Possible causes for this effect are discussed. Further, the combination of a light reflectance technique with photocurrent measurements allowed consideration of light absorption effects in the data treatment and separation of photocurrent contributions from the space‐charge layer from film‐thickness effects.

旋削加工における表面粗さのＬＱＩ制御

The present contribution is an attempt of the optimal machine tool control in turning to follow a desired tool position with better surface finish characteristics. In order to evaluate surface finishes during machining, a new simple measuring system has been proposed which uses an optical parallel substrate based on a light reflection technique. A tool position control by the LQI control is designed to reduce the tracking error between the tool and the workpiece surface. For this aim, a compensatory flat tool attached to the specially designed tool servo system is compensated for so that the tracking errors in following a desired tool position are removed. The improvements in surface finish are clarified by the roughness measurement with a stylus instrument.

A light reflectance technique for thickness measurements of passive films

A new in situ technique to determine the thickness of passive films is reported. In the present work, this technique is applied to the passive film on iron in borate buffer. The method is based on the light absorption of the oxide film for light energies higher than the band gap energy of the oxide. By using laser lines of 325 nm and 441 nm, the light absorption in the passive film on iron becomes accessible by measuring the difference in the reflectance of the electrode surface prior to and after passivation. The results for the absorption coefficient and for the film thickness obtained with this technique are in good agreement with values from the literature.

Formation and Dissolution of the Passive Film on Iron Studied by a Light Reflectance Technique

The formation, growth, and dissolution of the passive film on iron in neutral and alkaline solutions was investigated using a light reflectance technique. In this study, laser light of 325 nm was used to access the amount of light absorbed in the film and to evaluate the optical absorption coefficient. After calibration, this technique allows a fast, in situ determination of the film thickness. Cyclic voltammetry and potential‐step experiments with simultaneous thickness monitoring were carried out in borate buffer and in 0.1 M NaOH. For the borate buffer, anodic film formation and cathodic film dissolution are reversible, i.e., repeated anodic/cathodic cycling leads to conditions identical to the initial state. In NaOH, cathodic reduction of the film does not lead to film dissolution but to the formation of an electrochemically active layer, which does not significantly contribute to the potential drop in the metal/film/electrolyte system. Hence, repeated passivation and reduction leads to successive thickening of the film, consisting of a barrier layer of constant thickness and a porous layer having increased thickness with every passivation/reduction cycle. This layer does not contribute to the passivity of iron.

偏光反射異方性を用いた磁気記録媒体内粒子配向性の評価

The orientation of acicular Fe particles in magnetic coating media was investigated by the use of a polarized light reflection technique. The particle volume fraction, φP, of the magnetic coatings was changed from 30.5 to 53.7 vol%. The reflection ratio was compared with the squareness of the hysteresis for the coatings, measured by VSM, indicating the maximum value when plotted as a function of φP. The reflection intensity was strongly influenced by the surface roughness of the magnetic coatings. At a value of φP=45.1 vol%, the particles were well dispersed in the media, with the result that the coating surface became very smooth. The orientation of particles in a magnetic paint was also expressed as a function of the angle between the electric vector of the polarized light and the direction of the applied magnetic field. However, the reflection ratio as a function of another volume fraction, φPL, of the magnetic paints decreased with an increase in the apparent viscosity of the magnetic dispersion.

A Novel Iridescent Gel Phase of Surfactant and Order−Disorder Phase Separation Phenomena

A novel iridescent gel phase of surfactant has been found in a ternary mixture of a double-chain surfactant (triethanolammonium dihexadecylphosphate), water, and ethanol. The structure of the iridescent gel phase has been studied mainly by X-ray diffraction and ultraviolet and visible light reflection techniques and determined to be lamellar, having the spacing distance of a submicrometer. The color appearance of the solutions results from diffraction of visible light by the lamellar structure of bilayer membranes. It is particularly interesting to note in this system that the iridescent color can be changed with temperature (0−20 °C), ethanol concentration (15−48 wt %), and surfactant concentration (1.0−2.0 wt %) as well. The iridescent color begins to shift to the blue side at a certain critical temperature when the temperature is elevated. Turbidity of the solution also starts to increase at the same critical temperature. When these critical temperatures are connected as a function of surfactant concentration, a curve similar to that of the lower critical solution temperature type phase diagram is obtained. In the two-phase region of this diagram, the iridescent color changes with temperature, owing to the concentration change of the condensed (lamellar) phase, and does not change at constant temperature even when the surfactant concentration is altered. These novel phenomena in the present iridescent surfactant systems can be ascribed to the phase separation into a lamellar structure and disordered bilayers of the surfactant gel phase. This order−disorder phase transition is substantiated by the freeze−fracture electron microscopic technique. This new type of phase separation phenomenon gives us a challenging fundamental problem on the interactions between colloidal particles.

High-sensitive Pockels field sensor with a dielectric mirror

The highly sensitive field sensor with a Pockels crystal which was devised by us has been modified by using a light reflection technique. By replacing a metallic mirror with a dielectric mirror which is sputtered on one end face of the Pockels crystal, the new field measuring system has an advantage of precisely measuring the field distribution in the long gap discharge. This is the case when the field sensing part consisting of the Pockels crystal is isolated from the main field measuring system and both are connected to each other with a long light guide cable. Based on our experiments, we found that the measurable minimum field strength in the long gap discharge is 2 V/cm with the accuracy of 16 dB and 0.2 V/cm with the critical accuracy of 0 dB. Furthermore, we point out that the size of the field sensing part can be reduced down to 1 mm in diameter by using a dielectric mirror and a light guide cable.

Pupillary light reflex latency in patients with multiple sclerosis

In 46 patients with definite multiple sclerosis (MS) the direct and indirect pupillary light reflex latency (PLRL) and visual evoked potential (VEP) latency of the P100 were measured for each eye separately. The PLRL was measured at both photopic and scotopic illuminance level, using an infrared light reflection technique (IRIS). On average the PLRL increased at the scotopic illuminance level as compared with the photopic ( P<0.0001). An abnormal VEP was found in 80.4% of the patients, while 26.1% and 29.7% had an abnormal direct PLRL at photopic and scotopic illuminance level respectively. No correlations were found between PLRL and VEP or visual acuity. In MS patients with unilateral optic signs (optic neuritis or slowly progressive visual failure) a relative prolonged PLRL could be demonstrated in the symptomatic eye as compared to the asymptomatic eye. Based on formulae to quantitate relative afferent and efferent impairments of the pupillary pathway, it is demonstrated that prolonged PLRL measurements mainly reflect the nerve conduction in the efferent pupillary pathway.

Iridescent solutions resulting from periodic structure of bilayer membranes. 2

Iridescent aqueous solutions of dioctadecyldimethylammonium chloride (DOAC) have been newly found in the concentration range of 1-2 wt %. The structure of the solutions has been studied mainly by X-ray diffraction and ultraviolet and visible light reflection techniques and determined to be the lamellar liquid crystalline phase having the space distance of a submicrometer. The color appearance of the solutions results from diffraction of visible light by lamellar liquid crystalline structure of bilayer membranes. The mechanism of color appearance in DOAC solutions is the same as that of aqueous solutions of alkenylsuccinic acid, the structure of which is already elucidated by us. It is interesting to note, however, that the iridescent liquid crystalline phase of DOAC is understood to be thermodynamically metastable state, because of the following observations: (1) the iridescent-colored solutions can be obtained only by the sophisticated special procedures and (2) the color of the solutions disappears easily by weak agitations such as gentle shaking and/or stirring, and never recovers. It is worth noting, furthermore, in this DOAC system that the dramatic blue shift in the reflection spectra can be observed when the iridescent liquid crystal transforms into the gel phase on cooling. This blue-shift phenomenon might bemore » due to the phase separation into iridescent gel and water phases on gelation processes. 15 refs., 6 figs.« less

Uniform refractive index cladding for LiNbO3 single-crystal fibers

A uniform refractive index cladding for LiNbO3 single-crystal fibers has been achieved using a Mg ion indiffusion process. This cladding has a uniform MgO concentration of ∼20 mol %, resulting in a uniform refractive index. The refractive indices of the cladding material have been evaluated to be ne=2.08 and no=2.09 at 0.6328 μm by using the light reflection technique.

Stability of thin oil liquid films using mixed surfactants

A light reflectance technique has been used to determine the thickness of water-in-oil films stabilised with three oil-soluble surfactants taken singly and as mixtures. These surfactants were a non-ionic ABA block copolymer [A is poly(12-hydroxystearic acid) and B is poly(ethylene oxide); B246], Arlacel 83 (sorbitan sesquioleate) and soya bean lecithin. The film thicknesses, calculated using an iterative procedure, were generally in-keeping with a sterically-stabilised film. The values for B246 and Arlacel 83 were in agreement with calculated figures based on molecular models and with other experimental data both from this work and the literature. However, the lecithin films were inexplicably considerably thicker than anticipated. For the mixed films, film stability generally decreased with increasing lecithin content and the film thickness was dominated by the polymer at relatively low mole fractions.

Photoelectrochemistry of Highly Quantum Efficient Single‐Crystalline n ‐ FeS2 (Pyrite)

Monocrystalline (pyrite, ) photoelectrodes with high photocurrent quantum efficiency (> 90%) have been obtained by improvement of the solid‐state and interfacial chemistry. During intensive illumination (4–5 W/cm2), photocurrent densities between 1 and 2 A/cm2 have been observed for single crystals with high electron mobility in presence of the redox couple. Under illumination, a charge of 623.000 C/cm2 was passed without evidence of photocorrosion. The influence of etching treatments, various redox systems, and organic electrolytes on the photochemistry of was investigated. The formation and the dynamics of a thin oxidation layer that forms at the surface of the electrode in the presence of an acid electrolyte were studied using light reflection techniques and ESCA. has a valence energy band with strong d‐characterlike Mo‐ and W‐dichalcogenides, that is significant for its stabilization. An unresolved problem with this photoelectrode concerning applications in solar cells is the small photopotential which up to now does not exceed 200 mV (500 mV is theoretically possible). A strong pinning of the Fermi level by surface states is evident from photoelectrochemical measurements. In addition, it is expected that the distance between the conduction band and the Fermi level in our sample will be too large. A low effective carrier density was measured, resulting in an extended space‐charge layer, which has to be compared with the high absorption coefficient ( for ).

A rapid method of determination of betanin and vulgaxanthin I in beet powder using a general purpose tristimulus colorimeter

A general purpose tristimulus colorimeter was found to be adequate in determining beet powder pigments (betanin and vulgaxanthin I) concentrations. In comparison with the generally applied spectrophotometric method, the light-reflectance technique was found to be very accurate and reliable for determining the main beet pigments and could be used for rapid determination.

ChemInform Abstract: THE ANODIZATION OF SI IN AN RF PLASMA

AbstractDie Anodisierung von Si in einem 1 MHz‐Sauerstoffplasma wird beschrieben.

The Anodization of Si in an RF Plasma

The anodization of Si in a 1 MHz oxygen plasma is described. In‐situ film thickness measurements were made using a single angle “s” light reflectance technique and this data, coupled with information on the variation of sample voltage with thickness, was used to determine the dependence of ionic current on oxide field strength. The data for a given oxide thickness could be described by an equation of the form given by the theory of ionic conduction by a thermally activated, field‐assisted process. However, the ionic current and, in paticular, the oxide field strength were dependent on oxide thickness. MOS C‐V measurements on oxides of different thickness indicated a change in flatband voltage that could be attributed to a progressive build‐up of positive charge within the oxide. This space charge could be reduced by a low temperature annealing treatment. The oxides were found to be slightly absorbing optically, to have a relative permittivity in the range 3.5–3.9, and to possess good insulation properties as long as the oxide thickness did not exceed about 2500â.

Interactions of the horizontal and vertical human oculomotor systems: The vertical smooth pursuit and horizontal saccadic systems

The human oculomotor system has been studied by numerous people for well over half a century. Since the visual system is our primary sensory input channel, it is important for us to know how information is processed by the system. Most of the previous work on eye movements has been on modeling the horizontal eye movement control system. In the present series of experiments, human subjects were given the task of tracking a spot of light which moved both horizontally and vertically. The temporal relationship of the horizontal and vertical eye movements was recorded using a light reflection technique. The results of this experiment indicate that the horizontal saccadic and vertical smooth pursuit systems are parallel information processors and are not interdependent.

Interactions of the horizontal and vertical human oculomotor systems: The saccadic systems

The human oculomotor system has been studied by numerous people for well over half a century. Since the visual system is our primary sensory input channel, it is important for us to know how information is processed by the system. Most of the previous work on eye movements has been on modeling the horizontal eye movement control system. In the present series of experiments, human subjects were given the task of tracking a spot of light which moved both horizontally and vertically. The temporal relationship of the horizontal and vertical eye movements was recorded using a light reflection technique. The results of these experiments indicate that the horizontal and vertical saccadic systems are complexly interrelated. The phenomenon of the Psychological Refractory Period was observed. The interaction of the orthogonal saccadic systems may be due to visual information being processed in a parallel manner and motor activity being mediated by a serial processing stage.

Optical constants of carbons and coals in the infrared

A plane polarised light reflection technique has been used to measure the refractive and absorption indices of a series of carbons in the wavelength region one to ten microns at room temperature. The samples used consisted of coals and compressed soots, of various carbon contents, and a pyrographite. The tendency for materials of higher carbon content to have higher values of absorption and refractive indices, previously observed in the visible and u.v. region, is continued in the i.r.