The Experts below are selected from a list of 129 Experts worldwide ranked by ideXlab platform
Trevor J Wardill - One of the best experts on this subject based on the ideXlab platform.
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a novel setup for simultaneous two photon functional imaging and precise spectral and spatial visual stimulation in drosophila
Scientific Reports, 2020Co-Authors: Rachael C Feord, Trevor J WardillAbstract:Motion vision has been extensively characterised in Drosophila melanogaster, but substantially less is known about how flies process Colour, or how spectral information affects other visual modalities. To accurately dissect the components of the early visual system responsible for processing Colour, we developed a versatile visual stimulation setup to probe combined spatial, temporal and spectral response properties. Using flies expressing neural activity indicators, we tracked visual responses in the medulla, the second visual neuropil, to a projected Colour Stimulus. The introduction of custom bandpass optical filters enables simultaneous two-photon imaging and visual stimulation over a large range of wavelengths without compromising the temporal stimulation rate. With monochromator-produced light, any spectral bandwidth and centre wavelength from 390 to 730 nm can be selected to produce a narrow spectral hue. A specialised screen material scatters each band of light across the visible spectrum equally at all locations of the screen, thus enabling presentation of spatially structured stimuli. We show layer-specific shifts of spectral response properties in the medulla correlating with projection regions of photoreceptor terminals.
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a novel setup for simultaneous two photon functional imaging and precise spectral and spatial visual stimulation in drosophila
bioRxiv, 2020Co-Authors: Rachael C Feord, Trevor J WardillAbstract:Motion vision has been extensively characterized in Drosophila melanogaster, but substantially less is known about how flies process Colour, or how spectral information affects other visual modalities. To accurately dissect the components of the early visual system responsible for processing Colour, we developed a versatile visual stimulation setup to probe combined spatial, temporal and spectral response properties. Using flies expressing neural activity indicators, we tracked visual responses in the medulla to a projected Colour Stimulus (i.e. narrow bands of light). The introduction of custom Semrock bandpass optical filters enables simultaneous two-photon imaging and visual stimulation over a large range of wavelengths. A specialized screen material scatters each band of light across the spectrum equally at all locations of the screen, thus enabling presentation of spatially structured stimuli. We show layer-specific shifts of spectral response properties in the medulla correlating with projection regions of photoreceptor terminals.
Rachael C Feord - One of the best experts on this subject based on the ideXlab platform.
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a novel setup for simultaneous two photon functional imaging and precise spectral and spatial visual stimulation in drosophila
Scientific Reports, 2020Co-Authors: Rachael C Feord, Trevor J WardillAbstract:Motion vision has been extensively characterised in Drosophila melanogaster, but substantially less is known about how flies process Colour, or how spectral information affects other visual modalities. To accurately dissect the components of the early visual system responsible for processing Colour, we developed a versatile visual stimulation setup to probe combined spatial, temporal and spectral response properties. Using flies expressing neural activity indicators, we tracked visual responses in the medulla, the second visual neuropil, to a projected Colour Stimulus. The introduction of custom bandpass optical filters enables simultaneous two-photon imaging and visual stimulation over a large range of wavelengths without compromising the temporal stimulation rate. With monochromator-produced light, any spectral bandwidth and centre wavelength from 390 to 730 nm can be selected to produce a narrow spectral hue. A specialised screen material scatters each band of light across the visible spectrum equally at all locations of the screen, thus enabling presentation of spatially structured stimuli. We show layer-specific shifts of spectral response properties in the medulla correlating with projection regions of photoreceptor terminals.
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a novel setup for simultaneous two photon functional imaging and precise spectral and spatial visual stimulation in drosophila
bioRxiv, 2020Co-Authors: Rachael C Feord, Trevor J WardillAbstract:Motion vision has been extensively characterized in Drosophila melanogaster, but substantially less is known about how flies process Colour, or how spectral information affects other visual modalities. To accurately dissect the components of the early visual system responsible for processing Colour, we developed a versatile visual stimulation setup to probe combined spatial, temporal and spectral response properties. Using flies expressing neural activity indicators, we tracked visual responses in the medulla to a projected Colour Stimulus (i.e. narrow bands of light). The introduction of custom Semrock bandpass optical filters enables simultaneous two-photon imaging and visual stimulation over a large range of wavelengths. A specialized screen material scatters each band of light across the spectrum equally at all locations of the screen, thus enabling presentation of spatially structured stimuli. We show layer-specific shifts of spectral response properties in the medulla correlating with projection regions of photoreceptor terminals.
Thomas S Varley - One of the best experts on this subject based on the ideXlab platform.
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in situ spectroelectrochemistry and Colour measurement of a complementary electrochromic device based on surface confined prussian blue and aqueous solution phase methyl viologen
Solar Energy Materials and Solar Cells, 2012Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:Abstract The fabrication, in situ spectroelectrochemistry and Colour measurement of hybrid electrochromic devices (ECDs) based on a surface-confined metal hexacyanometallate – Prussian blue (PB, containing the iron(III) hexacyanoferrate(II) chromophore) – and aqueous solution-phase methyl viologen ( N , N ′-dimethyl-4,4′-bipyridylium) are described. In the ECDs, the initial (‘off’) bleached state is set with PB in its reduced form and the methyl viologen as the di-cation. Switching to the Coloured state (‘on’), forms the mixed-valence iron(III) hexacyanoferrate(II) chromophore upon oxidation of iron(II) hexacyanoferrate(II), with simultaneous reduction of the methyl viologen di-cation to form a mixture of the radical cation monomer/dimer. Using the Commission Internationale de l'Eclairage (CIE) system of colorimetry, the Colour Stimulus of such ECDs and the changes that take place on reversibly switching between the Colourless and Coloured states have been calculated from in situ visible region spectra recorded under electrochemical control. The concentration of the solution-phase methyl viologen and its diffusion to the cathode controlled both the proportion of surface-confined (reduced) PB that is switched to the blue form and the overall ECD changes. For the ECDs' ‘on’ states, the CIELAB 1976 Colour space coordinates for a D55 illuminant were L ⁎ =60, a ⁎ =3 and b ⁎ =−46, and L ⁎ =49, a ⁎ =9 and b ⁎ =−59, respectively for 5 and 10 mM methyl viologen solution concentrations. The low a ⁎ and high (negative) b ⁎ chromaticity coordinates quantified the overall ECD Colour Stimulus of the ‘on’ state as being deep blue, with a broad absorption across the visible spectral region. CIELAB 1976 Colour space coordinates showed that the ECDs were fully transparent and nearly Colourless in the ‘off’ states, with L ⁎ =100, a ⁎ =1 and b ⁎ =1. The changes in the transparency were 83.0% (5 mM methyl viologen) and 93.1% (10 mM methyl viologen) between the ‘off’ (bleached) and ‘on’ (Coloured) states of the ECDs.
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Advances in electrochromic materials
2011Co-Authors: Thomas S VarleyAbstract:The development of a Microsoft® Excel® spreadsheet is described, for the accurate calculation of CIE (Commission Internationale de l’Eclairage) 1931 xy chromaticity coordinates and luminance data from visible region absorption spectra recorded in transmission mode. Using firmly established CIE principles, absorbance-wavelength data from visible spectra are taken as input, with chromaticity coordinates being generated as output. Colour Stimulus measurement example calculation results are firstly presented for aqueous solutions of the dyes, Erythrosin B (red, x, y = 0.608, 0.365), Acid Green 25 (x, y = 0.086, 0.298) and Remaxol Brilliant Blue R (x, y = 0.153, 0.045), and then for tracking electrochromic in situ Colour Stimulus changes in the methyl viologen and di-n-heptyl viologen systems. The quantification of Colour during each viologen dication to cationradical reduction process, and each reverse (oxidation) process, showed that subtle changes in both hue and luminance could be detected, with evidence of Colour contributions from both the cation radical and the cation radical dimer. Ruthenium purple (RP) films on transmissive tin-doped indium oxide (ITO)/glass substrates have been synthesised by a novel electrochemical coagulation technique. Using the CIE system of colorimetry, the Colour Stimulus of the electrochromic RP films and the changes that take place on reversibly switching to the Colourless form have been calculated from in situ visible spectra recorded under electrochemical control. (Continues...).
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quantification of Colour stimuli through the calculation of cie chromaticity coordinates and luminance data for application to in situ colorimetry studies of electrochromic materials
Displays, 2011Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:The development of a Microsoft® Excel® spreadsheet is described, for the accurate calculation of CIE (Commission Internationale de l’Eclairage) 1931 xy chromaticity coordinates and luminance data from visible region absorption spectra recorded in transmission mode. Using firmly established CIE principles, absorbance-wavelength data from visible spectra recorded using a Hewlett Packard 8452A diode array spectrophotometer are taken as input, with chromaticity coordinates being generated as output. The colorimetric transformations described are well known to Colour scientists, with the methodology and background now being made accessible to the electrochromic materials community. Colour Stimulus measurement example calculation results are firstly presented for aqueous solutions of the dyes, Erythrosin B (red), Acid Green 25 and Remaxol Brilliant Blue R, and then for tracking electrochromic in situ Colour Stimulus changes in the methyl viologen and n-heptyl viologen systems. The quantification of Colour during each viologen dication to cation radical reduction process, and each reverse (oxidation) process, showed that subtle changes in both hue and luminance could be detected, with evidence of Colour contributions from both the cation radical and the cation radical dimer.
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Synthesis, characterisation and in situ colorimetry of electrochromic Ruthenium purple thin films
Dyes and Pigments, 2011Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:Ruthenium purple (RP) films on transmissive tin-doped indium oxide (ITO)/glass substrates have been synthesised by an electrochemical coagulation technique using an aqueous RP colloidal suspension prepared from separate very dilute aqueous solutions of iron(III) chloride and potassium hexacyanoruthenate(II), with dilute potassium chloride as supporting electrolyte solution. To aid stability of the RP films, ruthenium(III) chloride was added to the RP colloidal suspension. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry, the Colour Stimulus of the electrochromic RP films and the changes that take place on reversibly switching to the Colourless form have been calculated from in situ visible spectra recorded under electrochemical control. On electrochemical reduction, the intensely absorbing bright purple mixed-valence iron(III) hexacyanoruthenate(II) chromophore is reduced to the Colourless iron(II) hexacyanoruthenate(II) form. Sharp and reversible changes in the hue and saturation occur, as shown by the track of the CIE 1931 xy chromaticity coordinates. Concurrently, as the purple chromophore is bleached, a large increase in the relative luminance of the electrochromic film is observed. For the purple state, the CIELAB 1976 Colour space coordinates were L* = 64, a* = 27 and b* = −36, with a complementary wavelength (λc) calculated as 555 nm, in excellent agreement with the absorption maximum (λmax) of 550 nm for the intervalence charge-transfer (IVCT) band.
Roger J Mortimer - One of the best experts on this subject based on the ideXlab platform.
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in situ spectroelectrochemistry and Colour measurement of a complementary electrochromic device based on surface confined prussian blue and aqueous solution phase methyl viologen
Solar Energy Materials and Solar Cells, 2012Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:Abstract The fabrication, in situ spectroelectrochemistry and Colour measurement of hybrid electrochromic devices (ECDs) based on a surface-confined metal hexacyanometallate – Prussian blue (PB, containing the iron(III) hexacyanoferrate(II) chromophore) – and aqueous solution-phase methyl viologen ( N , N ′-dimethyl-4,4′-bipyridylium) are described. In the ECDs, the initial (‘off’) bleached state is set with PB in its reduced form and the methyl viologen as the di-cation. Switching to the Coloured state (‘on’), forms the mixed-valence iron(III) hexacyanoferrate(II) chromophore upon oxidation of iron(II) hexacyanoferrate(II), with simultaneous reduction of the methyl viologen di-cation to form a mixture of the radical cation monomer/dimer. Using the Commission Internationale de l'Eclairage (CIE) system of colorimetry, the Colour Stimulus of such ECDs and the changes that take place on reversibly switching between the Colourless and Coloured states have been calculated from in situ visible region spectra recorded under electrochemical control. The concentration of the solution-phase methyl viologen and its diffusion to the cathode controlled both the proportion of surface-confined (reduced) PB that is switched to the blue form and the overall ECD changes. For the ECDs' ‘on’ states, the CIELAB 1976 Colour space coordinates for a D55 illuminant were L ⁎ =60, a ⁎ =3 and b ⁎ =−46, and L ⁎ =49, a ⁎ =9 and b ⁎ =−59, respectively for 5 and 10 mM methyl viologen solution concentrations. The low a ⁎ and high (negative) b ⁎ chromaticity coordinates quantified the overall ECD Colour Stimulus of the ‘on’ state as being deep blue, with a broad absorption across the visible spectral region. CIELAB 1976 Colour space coordinates showed that the ECDs were fully transparent and nearly Colourless in the ‘off’ states, with L ⁎ =100, a ⁎ =1 and b ⁎ =1. The changes in the transparency were 83.0% (5 mM methyl viologen) and 93.1% (10 mM methyl viologen) between the ‘off’ (bleached) and ‘on’ (Coloured) states of the ECDs.
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quantification of Colour stimuli through the calculation of cie chromaticity coordinates and luminance data for application to in situ colorimetry studies of electrochromic materials
Displays, 2011Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:The development of a Microsoft® Excel® spreadsheet is described, for the accurate calculation of CIE (Commission Internationale de l’Eclairage) 1931 xy chromaticity coordinates and luminance data from visible region absorption spectra recorded in transmission mode. Using firmly established CIE principles, absorbance-wavelength data from visible spectra recorded using a Hewlett Packard 8452A diode array spectrophotometer are taken as input, with chromaticity coordinates being generated as output. The colorimetric transformations described are well known to Colour scientists, with the methodology and background now being made accessible to the electrochromic materials community. Colour Stimulus measurement example calculation results are firstly presented for aqueous solutions of the dyes, Erythrosin B (red), Acid Green 25 and Remaxol Brilliant Blue R, and then for tracking electrochromic in situ Colour Stimulus changes in the methyl viologen and n-heptyl viologen systems. The quantification of Colour during each viologen dication to cation radical reduction process, and each reverse (oxidation) process, showed that subtle changes in both hue and luminance could be detected, with evidence of Colour contributions from both the cation radical and the cation radical dimer.
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Synthesis, characterisation and in situ colorimetry of electrochromic Ruthenium purple thin films
Dyes and Pigments, 2011Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:Ruthenium purple (RP) films on transmissive tin-doped indium oxide (ITO)/glass substrates have been synthesised by an electrochemical coagulation technique using an aqueous RP colloidal suspension prepared from separate very dilute aqueous solutions of iron(III) chloride and potassium hexacyanoruthenate(II), with dilute potassium chloride as supporting electrolyte solution. To aid stability of the RP films, ruthenium(III) chloride was added to the RP colloidal suspension. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry, the Colour Stimulus of the electrochromic RP films and the changes that take place on reversibly switching to the Colourless form have been calculated from in situ visible spectra recorded under electrochemical control. On electrochemical reduction, the intensely absorbing bright purple mixed-valence iron(III) hexacyanoruthenate(II) chromophore is reduced to the Colourless iron(II) hexacyanoruthenate(II) form. Sharp and reversible changes in the hue and saturation occur, as shown by the track of the CIE 1931 xy chromaticity coordinates. Concurrently, as the purple chromophore is bleached, a large increase in the relative luminance of the electrochromic film is observed. For the purple state, the CIELAB 1976 Colour space coordinates were L* = 64, a* = 27 and b* = −36, with a complementary wavelength (λc) calculated as 555 nm, in excellent agreement with the absorption maximum (λmax) of 550 nm for the intervalence charge-transfer (IVCT) band.
Jasna Martinovic - One of the best experts on this subject based on the ideXlab platform.
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Low-level and high-level modulations of fixational saccades and high frequency oscillatory brain activity in a visual object classification task.
Frontiers in psychology, 2013Co-Authors: Maciej Kosilo, Sophie Wuerger, Matt Craddock, Ben J. Jennings, Amelia R. Hunt, Jasna MartinovicAbstract:Until recently induced gamma-band activity (GBA) was considered a neural marker of cortical object representation. However induced GBA in the electroencephalogram (EEG) is susceptible to artifacts caused by miniature fixational saccades. Recent studies have demonstrated that fixational saccades also reflect high-level representational processes. Do high-level as opposed to low-level factors influence fixational saccades? What is the effect of these factors on artifact-free GBA? To investigate this, we conducted separate eye tracking and EEG experiments using identical designs. Participants classified line drawings as objects or non-objects. To introduce low-level differences, contours were defined along different directions in cardinal Colour space: S-cone-isolating, intermediate isoluminant, or a full-Colour Stimulus, the latter containing an additional achromatic component. Prior to the classification task, object discrimination thresholds were measured and stimuli were scaled to matching suprathreshold levels for each participant. In both experiments, behavioural performance was best for full-Colour stimuli and worst for S-cone isolating stimuli. Saccade rates 200-700 ms after Stimulus onset were modulated independently by low and high-level factors, being higher for full-Colour stimuli than for S-cone isolating stimuli and higher for objects. Low-amplitude evoked GBA and total GBA were observed in very few conditions, showing that paradigms with isoluminant stimuli may not be ideal for eliciting such responses. We conclude that cortical loops involved in the processing of objects are preferentially excited by stimuli that contain achromatic information. Their activation can lead to relatively early exploratory eye movements even for foveally-presented stimuli.