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Kirill S. Napolskii - One of the best experts on this subject based on the ideXlab platform.

  • High-quality-factor anodic alumina Optical microcavities prepared by cyclic anodizing with voltage versus Optical Path Length modulation
    Journal of Materials Chemistry C, 2020
    Co-Authors: S. E. Kushnir, Tatiana Yu. Komarova, Kirill S. Napolskii
    Abstract:

    Anodic alumina Optical microcavities with precisely tuned positions of intense resonance bands within the range of 250–1500 nm are prepared by cyclic anodizing with voltage versus Optical Path Length modulation. Among the structures obtained by anodizing, the fabricated Optical microcavities possess an unprecedentedly high quality factor of 209–269.

  • Anodizing with voltage versus Optical Path Length modulation: a new tool for the preparation of photonic structures
    Journal of Materials Chemistry C, 2018
    Co-Authors: S. E. Kushnir, Tatyana Yu Pchelyakova, Kirill S. Napolskii
    Abstract:

    One-dimensional photonic crystals – multilayered structures with periodic modulation of a refractive index – are of great practical importance in modern materials science and nanotechnology owing to a variety of their applications in optoelectronics, solar photovoltaics, and sensorics. Anodizing of valve metals under oscillating conditions, which allows one to produce porous oxide films with modulated porosity across the film thickness, is a low-cost, scalable, and reproducible method for the preparation of 1D photonic crystals. However, precise control of the refractive index and the Optical Path Length of the single layers in anodic oxides is still a challenge, mainly due to the chemical widening of pores in the upper part of the oxide film during the anodizing and, thus destruction of the structural periodicity produced electrochemically. Here, a novel anodizing regime with feedback, which takes into account the rate of chemical etching as a parameter, is suggested for the precise control of morphology of the porous films of anodic oxides of valve metals. The suggested approach allows one to apply anodizing voltage as a function of the Optical Path Length of an oxide layer. The potential of the suggested approach is demonstrated by the preparation of one-dimensional anodic alumina photonic crystals with an unprecedentedly high quality factor of the photonic band gaps. The possibility to tune the position of a photonic band gap within the range of 250–1400 nm with an inaccuracy of

Eiji Okada - One of the best experts on this subject based on the ideXlab platform.

  • Influence of Optical Path Length on multi-waveLength measurement of oxy- and deoxy-hemoglobins in the skin
    Diffuse Optical Spectroscopy and Imaging VII, 2019
    Co-Authors: Taiki Shirai, Eiji Okada
    Abstract:

    The changes in the oxy- and deoxygenated hemoglobins at different depths of skin tissue were obtained from the diffuse reflectance spectra in three waveLength ranges of the skin. The influence of the Optical Path Length in the calculation on the results of the hemoglobin change was evaluated.

  • Partial Optical Path Length in the scalp in subject-specific head models for multi-distance probe configuration of near infrared spectroscopy
    Biomedical Imaging and Sensing Conference, 2018
    Co-Authors: Taku Yanagisawa, Hiroshi Kawaguchi, Takayuki Obata, Eiji Okada
    Abstract:

    In the brain function measurement by near infrared spectroscopy using a multi-distance probe configuration, the ratio of the partial Optical Path Length in the scalp for the long spacing probe pair to that for the short spacing probe pair is important for the calculation to eliminate the scalp component in the signal. Light propagation in the subject specific head models of 45 volunteers was calculated to predict the dependence of the partial Optical Path Length in the scalp and the weighting factor for the multi-distance probe configuration. The weighting factor ranges from 1.0 to 2.3 and increases with the scalp thickness when the scalp thickness is less than 15 mm.

  • Estimation of partial Optical Path Length in the brain in subject-specific head models for near-infrared spectroscopy
    Optical Review, 2016
    Co-Authors: Kotaro Nakamura, Kazuki Kurihara, Hiroshi Kawaguchi, Takayuki Obata, Hiroshi Ito, Eiji Okada
    Abstract:

    Three-dimensional head models with the structures constructed from the MR head images of 40 volunteers were constructed to analyze light propagation in the subject-specific head models. The mean Optical Path Length in the head and the partial Optical Path Length in the brain at 13 fiducial points for each volunteer were estimated to evaluate the intersubject and spatial variability in the Optical Path Lengths. Although the intersubject variability in the Optical Path Lengths is very high, the spatial variability in the average of the mean Optical Path Length and partial Optical Path Length is similar to the previously reported data. The mean Optical Path Length in the head increases, whereas the partial Optical Path Length in the brain decreases with an increase in the depth of the brain surface. The partial Optical Path Length is highly correlated with the depth of the brain surface in comparison to the mean Optical Path Length in the head.

  • WaveLength dependence of partial Optical Path Length in the vascular plexus of reflected light of the skin
    Biomedical Optics 2016, 2016
    Co-Authors: Rina Sato, Kazuki Kurihara, Minami Kato, Eiji Okada
    Abstract:

    The Optical Path Length in the vascular plexus of the skin was estimated. The heterogeneity of the hemoglobin concentration in the dermis significantly contributes to the waveLength dependence of the reflectance of the skin.

  • Estimation of the Optical Path Length factor for functional imaging of an exposed cortex by principal component analysis
    Photon Migration and Diffuse-Light Imaging, 2003
    Co-Authors: Kentaro Yokoyama, Motoshi Watanabe, Eiji Okada
    Abstract:

    Activation of the cerebral cortex induces a localized change in the volume and oxygenation of the blood. Because the change in spectral reflectance of the cortex depends upon the concentration changes in oxy- and deoxy haemoglobin, multi-spectral imaging has been applied to investigate the functional activity of the exposed cortex related to oxy- and deoxy haemoglobin. However, brain tissue is a highly scattering medium, and the reflectance of cortical tissue depends on the mean Optical Path Length of the detected light. The linear spectrographic analysis method without waveLength-dependent Path Length scaling may produce unreliable results in multi-spectral image analysis. In this study, we propose a method of estimating the waveLength-dependent Path Length factor from the principal component analysis of the multi-spectral images of the exposed cortex. The Optical Path-Length factor estimated from the first principal component of the multi-spectral image of the cortical model and the absorption spectrum of haemoglobin agrees with that predicted by Monte Carlo simulation. The tendency of the Optical Path-Length factor of the pig brain estimated from the first principal component of the multi-spectral images is almost the same as that of the cortical model.

S. E. Kushnir - One of the best experts on this subject based on the ideXlab platform.

  • High-quality-factor anodic alumina Optical microcavities prepared by cyclic anodizing with voltage versus Optical Path Length modulation
    Journal of Materials Chemistry C, 2020
    Co-Authors: S. E. Kushnir, Tatiana Yu. Komarova, Kirill S. Napolskii
    Abstract:

    Anodic alumina Optical microcavities with precisely tuned positions of intense resonance bands within the range of 250–1500 nm are prepared by cyclic anodizing with voltage versus Optical Path Length modulation. Among the structures obtained by anodizing, the fabricated Optical microcavities possess an unprecedentedly high quality factor of 209–269.

  • Anodizing with voltage versus Optical Path Length modulation: a new tool for the preparation of photonic structures
    Journal of Materials Chemistry C, 2018
    Co-Authors: S. E. Kushnir, Tatyana Yu Pchelyakova, Kirill S. Napolskii
    Abstract:

    One-dimensional photonic crystals – multilayered structures with periodic modulation of a refractive index – are of great practical importance in modern materials science and nanotechnology owing to a variety of their applications in optoelectronics, solar photovoltaics, and sensorics. Anodizing of valve metals under oscillating conditions, which allows one to produce porous oxide films with modulated porosity across the film thickness, is a low-cost, scalable, and reproducible method for the preparation of 1D photonic crystals. However, precise control of the refractive index and the Optical Path Length of the single layers in anodic oxides is still a challenge, mainly due to the chemical widening of pores in the upper part of the oxide film during the anodizing and, thus destruction of the structural periodicity produced electrochemically. Here, a novel anodizing regime with feedback, which takes into account the rate of chemical etching as a parameter, is suggested for the precise control of morphology of the porous films of anodic oxides of valve metals. The suggested approach allows one to apply anodizing voltage as a function of the Optical Path Length of an oxide layer. The potential of the suggested approach is demonstrated by the preparation of one-dimensional anodic alumina photonic crystals with an unprecedentedly high quality factor of the photonic band gaps. The possibility to tune the position of a photonic band gap within the range of 250–1400 nm with an inaccuracy of

Britton Chance - One of the best experts on this subject based on the ideXlab platform.

  • transcranial Optical Path Length in infants by near infrared phase shift spectroscopy
    Journal of Clinical Monitoring and Computing, 1995
    Co-Authors: D A Benaron, C D Kurth, James M Steven, M Delivoriapapadopoulos, Britton Chance
    Abstract:

    Background. Near-infrared spectroscopy (NIRS) is an emerging technique for noninvasive, bedside monitoring of cerebral oxygenation and blood flow. Traditionally, it has relied on the Beer's Law relationship in which the concentration of light-absorbing oxygen-carrying pigments is proportional to their light absorbance, and inversely proportional to an Optical Path Length (a measure of the distance traveled by photons passing through the tissue). In practice, NIRS has been based upon assumptions that mean transcranial Optical Path Length, the average Optical Path Length for a given patient, is constant among patients and independent of the waveLength of light used.Objective. The objective of our study was to measure mean Optical transcranial Path Length in infants as a step in allowing quantitation of cerebral oxygenation.Methods. We measured mean transcranial Optical Path Length in 34 infants, aged 1 day to 3 years, using amplitude-modulated phase-shift spectroscopy at 754 nm and 816 nm. Optical transcranial Path Lengths (mean±SEM) were 8.6±0.9 cm, 11.1±0.9 cm, and 11.3±0.9 cm at 754 nm, and 8.8±0.9 cm, 11.2±0.8 cm, and 11.1±0.9 cm at 816 nm, using emitter-detector separations of 1.8, 2.5, and 3.0 cm, respectively. Optical Path Length increased as emitter-detector separation, head circumference, or age increased. Variance in the ratio of mean Optical Path Lengths at the two different waveLengths exceeded that accounted for by variation in repeated measures alone (p<0.001), suggesting that Optical Path Length is also not independent of waveLength.Conclusions. NIRS instrument emitter-detector geometry, subject age, head size, and waveLength used each influence Optical Path Length. Quantitative NIRS measurements in clinical use may require concurrent measurement of both absorbance and Optical Path Length at each waveLength, or use of newer measures that are not based upon Beer's Law assumptions.

  • Transcranial Optical Path Length in infants by near-infrared phase-shift spectroscopy.
    Journal of clinical monitoring, 1995
    Co-Authors: D A Benaron, C D Kurth, James M Steven, M. Delivoria-papadopoulos, Britton Chance
    Abstract:

    Background. Near-infrared spectroscopy (NIRS) is an emerging technique for noninvasive, bedside monitoring of cerebral oxygenation and blood flow. Traditionally, it has relied on the Beer's Law relationship in which the concentration of light-absorbing oxygen-carrying pigments is proportional to their light absorbance, and inversely proportional to an Optical Path Length (a measure of the distance traveled by photons passing through the tissue). In practice, NIRS has been based upon assumptions that mean transcranial Optical Path Length, the average Optical Path Length for a given patient, is constant among patients and independent of the waveLength of light used.Objective. The objective of our study was to measure mean Optical transcranial Path Length in infants as a step in allowing quantitation of cerebral oxygenation.Methods. We measured mean transcranial Optical Path Length in 34 infants, aged 1 day to 3 years, using amplitude-modulated phase-shift spectroscopy at 754 nm and 816 nm. Optical transcranial Path Lengths (mean±SEM) were 8.6±0.9 cm, 11.1±0.9 cm, and 11.3±0.9 cm at 754 nm, and 8.8±0.9 cm, 11.2±0.8 cm, and 11.1±0.9 cm at 816 nm, using emitter-detector separations of 1.8, 2.5, and 3.0 cm, respectively. Optical Path Length increased as emitter-detector separation, head circumference, or age increased. Variance in the ratio of mean Optical Path Lengths at the two different waveLengths exceeded that accounted for by variation in repeated measures alone (p

D A Benaron - One of the best experts on this subject based on the ideXlab platform.

  • transcranial Optical Path Length in infants by near infrared phase shift spectroscopy
    Journal of Clinical Monitoring and Computing, 1995
    Co-Authors: D A Benaron, C D Kurth, James M Steven, M Delivoriapapadopoulos, Britton Chance
    Abstract:

    Background. Near-infrared spectroscopy (NIRS) is an emerging technique for noninvasive, bedside monitoring of cerebral oxygenation and blood flow. Traditionally, it has relied on the Beer's Law relationship in which the concentration of light-absorbing oxygen-carrying pigments is proportional to their light absorbance, and inversely proportional to an Optical Path Length (a measure of the distance traveled by photons passing through the tissue). In practice, NIRS has been based upon assumptions that mean transcranial Optical Path Length, the average Optical Path Length for a given patient, is constant among patients and independent of the waveLength of light used.Objective. The objective of our study was to measure mean Optical transcranial Path Length in infants as a step in allowing quantitation of cerebral oxygenation.Methods. We measured mean transcranial Optical Path Length in 34 infants, aged 1 day to 3 years, using amplitude-modulated phase-shift spectroscopy at 754 nm and 816 nm. Optical transcranial Path Lengths (mean±SEM) were 8.6±0.9 cm, 11.1±0.9 cm, and 11.3±0.9 cm at 754 nm, and 8.8±0.9 cm, 11.2±0.8 cm, and 11.1±0.9 cm at 816 nm, using emitter-detector separations of 1.8, 2.5, and 3.0 cm, respectively. Optical Path Length increased as emitter-detector separation, head circumference, or age increased. Variance in the ratio of mean Optical Path Lengths at the two different waveLengths exceeded that accounted for by variation in repeated measures alone (p<0.001), suggesting that Optical Path Length is also not independent of waveLength.Conclusions. NIRS instrument emitter-detector geometry, subject age, head size, and waveLength used each influence Optical Path Length. Quantitative NIRS measurements in clinical use may require concurrent measurement of both absorbance and Optical Path Length at each waveLength, or use of newer measures that are not based upon Beer's Law assumptions.

  • Transcranial Optical Path Length in infants by near-infrared phase-shift spectroscopy.
    Journal of clinical monitoring, 1995
    Co-Authors: D A Benaron, C D Kurth, James M Steven, M. Delivoria-papadopoulos, Britton Chance
    Abstract:

    Background. Near-infrared spectroscopy (NIRS) is an emerging technique for noninvasive, bedside monitoring of cerebral oxygenation and blood flow. Traditionally, it has relied on the Beer's Law relationship in which the concentration of light-absorbing oxygen-carrying pigments is proportional to their light absorbance, and inversely proportional to an Optical Path Length (a measure of the distance traveled by photons passing through the tissue). In practice, NIRS has been based upon assumptions that mean transcranial Optical Path Length, the average Optical Path Length for a given patient, is constant among patients and independent of the waveLength of light used.Objective. The objective of our study was to measure mean Optical transcranial Path Length in infants as a step in allowing quantitation of cerebral oxygenation.Methods. We measured mean transcranial Optical Path Length in 34 infants, aged 1 day to 3 years, using amplitude-modulated phase-shift spectroscopy at 754 nm and 816 nm. Optical transcranial Path Lengths (mean±SEM) were 8.6±0.9 cm, 11.1±0.9 cm, and 11.3±0.9 cm at 754 nm, and 8.8±0.9 cm, 11.2±0.8 cm, and 11.1±0.9 cm at 816 nm, using emitter-detector separations of 1.8, 2.5, and 3.0 cm, respectively. Optical Path Length increased as emitter-detector separation, head circumference, or age increased. Variance in the ratio of mean Optical Path Lengths at the two different waveLengths exceeded that accounted for by variation in repeated measures alone (p