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Paul A Sieving - One of the best experts on this subject based on the ideXlab platform.
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Primate photopic Sine-Wave flicker ERG: vector modeling analysis of component origins using glutamate analogs. Invest Ophthalmol Vis Sci
2020Co-Authors: Mineo Kondo, Paul A SievingAbstract:PURPOSE. To study how the photoreceptoral and postreceptoral ON-and OFF-components contribute to the photopic SineWave flicker ERG in the monkey by isolating the components with glutamate analogs. METHODS. Monkey photopic flicker ERGs were elicited with Sine Wave stimuli (mean luminance, 2.66 log cd/m 2 ; 80% modulation depth, on a 40 cd/m 2 white background) and were recorded for stimulus frequencies of 4 Hz to 64 Hz, before and after intravitreal injection of DL-2-amino-4-phosphonobutyric acid (APB) and cis-2,3-piperidinedicarboxylic acid (PDA) that block ON-and OFF-bipolar activity, respectively. The amplitude and phase of the fundamental component were analyzed. RESULTS. The flicker response amplitudes increased after APB, for frequencies of 6 Hz to 32 Hz. The further addition of PDA to isolate the photoreceptor component resulted in a relatively small residual response that decreased monotonically from 4 Hz to 32 Hz. The postsynaptic APB (ON-) and PDA (OFF-) sensitive components were isolated by subtraction and were characterized by amplitude and phase vectors. The ON-and OFF-components were larger than the initial control responses for stimuli of 8 Hz to 40 Hz. These two components had a frequency-dependent phase difference of 160°to 230°; normally, they interfere with each other and reduce their net contribution. The phase difference between ON-and OFFcomponents was nearly 180°for a 10-Hz stimulus, and the phase cancellation caused a prominent dip in amplitude at this frequency. CONCLUSIONS. These results indicate that postreceptoral ONand OFF-components contribute substantially to the Sine-Wave flicker ERG, especially at higher stimulus frequencies. Because of phase cancellation, they mask each other in the net response in a frequency dependent fashion. The photoreceptor contribution is greater than the net postsynaptic component only for frequencies of approximately less than or equal to 10 Hz. These results can be summarized by a vector model that may be useful for interpreting changes resulting from retinal disease. (Invest Ophthalmol Vis Sci. 2001;42:305-312) T he contribution of the different retinal elements to the fast flicker ERG has not been determined precisely in the primate. Earlier studies indicated an outer retinal locus for the fast flicker ERG signals. 1-7 Baron, Boynton, and colleagues 6 -8 However, Donovan and Baron 2 found a disparity between intraretinal local ERG (LERG) responses and the corneal flicker response, which led them to wonder whether additional components might be contributing to the corneal flicker ERG beyond the intraretinal receptor potentials. Chang et al. 9 also suggest the possibility of postreceptoral contribution to the Sine-Wave flicker ERGs. It is known that the retinal response to Sine-Wave flicker stimuli is dominated by a component at the same temporal frequency as the stimulus, termed the fundamental component. However, under some conditions, a component is seen at twice the stimulus frequency (i.e., a second harmonic component). 10 -13 Current source density analysis 14 suggested that the fundamental component was dominated by photoreceptor activity, yet the second harmonic component originated from multiple retinal sources and included contributions from the middle and inner retina. A systems analytic approach in humans 12,13 also agreed with a model of the Sine-Wave flicker ERG that attributed the majority of the linear (or fundamental) component to photoreceptor-related processes, particularly at medium and high frequencies. Some clinical studies Previously, the authors studied the photopic fast flicker ERG using square Waves and photostrobe flashes 17 and found that the corneal response was virtually eliminated by aspartate or by the combination of DL-2-amino-4-phosphonobutyric acid (APB) 18 plus cis-2,3-piperidinedicarboxylic acid (PDA). 19 These drugs block transmission to the second-order neurons postsynaptic to cones. This study revisited the question of the origins of the primate flicker ERG and recorded Sine-Wave flicker responses from monkeys over a wide range of temporal frequencies on a photopic background before and after applying glutamate analogs. Particular attention was given to the nature of the fundamental frequency component
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primate photopic Sine Wave flicker erg vector modeling analysis of component origins using glutamate analogs
Investigative Ophthalmology & Visual Science, 2001Co-Authors: Mineo Kondo, Paul A SievingAbstract:Purpose To study how the photoreceptoral and postreceptoral ON- and OFF-components contribute to the photopic Sine-Wave flicker ERG in the monkey by isolating the components with glutamate analogs. Methods Monkey photopic flicker ERGs were elicited with Sine Wave stimuli (mean luminance, 2.66 log cd/m(2); 80% modulation depth, on a 40 cd/m(2) white background) and were recorded for stimulus frequencies of 4 Hz to 64 Hz, before and after intravitreal injection of DL-2-amino-4-phosphonobutyric acid (APB) and cis-2, 3-piperidinedicarboxylic acid (PDA) that block ON- and OFF-bipolar activity, respectively. The amplitude and phase of the fundamental component were analyzed. Results The flicker response amplitudes increased after APB, for frequencies of 6 Hz to 32 Hz. The further addition of PDA to isolate the photoreceptor component resulted in a relatively small residual response that decreased monotonically from 4 Hz to 32 Hz. The postsynaptic APB (ON-) and PDA (OFF-) sensitive components were isolated by subtraction and were characterized by amplitude and phase vectors. The ON- and OFF-components were larger than the initial control responses for stimuli of 8 Hz to 40 Hz. These two components had a frequency-dependent phase difference of 160 degrees to 230 degrees; normally, they interfere with each other and reduce their net contribution. The phase difference between ON- and OFF-components was nearly 180 degrees for a 10-Hz stimulus, and the phase cancellation caused a prominent dip in amplitude at this frequency. Conclusions These results indicate that postreceptoral ON- and OFF-components contribute substantially to the Sine-Wave flicker ERG, especially at higher stimulus frequencies. Because of phase cancellation, they mask each other in the net response in a frequency dependent fashion. The photoreceptor contribution is greater than the net postsynaptic component only for frequencies of approximately less than or equal to 10 Hz. These results can be summarized by a vector model that may be useful for interpreting changes resulting from retinal disease.
Mineo Kondo - One of the best experts on this subject based on the ideXlab platform.
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Primate photopic Sine-Wave flicker ERG: vector modeling analysis of component origins using glutamate analogs. Invest Ophthalmol Vis Sci
2020Co-Authors: Mineo Kondo, Paul A SievingAbstract:PURPOSE. To study how the photoreceptoral and postreceptoral ON-and OFF-components contribute to the photopic SineWave flicker ERG in the monkey by isolating the components with glutamate analogs. METHODS. Monkey photopic flicker ERGs were elicited with Sine Wave stimuli (mean luminance, 2.66 log cd/m 2 ; 80% modulation depth, on a 40 cd/m 2 white background) and were recorded for stimulus frequencies of 4 Hz to 64 Hz, before and after intravitreal injection of DL-2-amino-4-phosphonobutyric acid (APB) and cis-2,3-piperidinedicarboxylic acid (PDA) that block ON-and OFF-bipolar activity, respectively. The amplitude and phase of the fundamental component were analyzed. RESULTS. The flicker response amplitudes increased after APB, for frequencies of 6 Hz to 32 Hz. The further addition of PDA to isolate the photoreceptor component resulted in a relatively small residual response that decreased monotonically from 4 Hz to 32 Hz. The postsynaptic APB (ON-) and PDA (OFF-) sensitive components were isolated by subtraction and were characterized by amplitude and phase vectors. The ON-and OFF-components were larger than the initial control responses for stimuli of 8 Hz to 40 Hz. These two components had a frequency-dependent phase difference of 160°to 230°; normally, they interfere with each other and reduce their net contribution. The phase difference between ON-and OFFcomponents was nearly 180°for a 10-Hz stimulus, and the phase cancellation caused a prominent dip in amplitude at this frequency. CONCLUSIONS. These results indicate that postreceptoral ONand OFF-components contribute substantially to the Sine-Wave flicker ERG, especially at higher stimulus frequencies. Because of phase cancellation, they mask each other in the net response in a frequency dependent fashion. The photoreceptor contribution is greater than the net postsynaptic component only for frequencies of approximately less than or equal to 10 Hz. These results can be summarized by a vector model that may be useful for interpreting changes resulting from retinal disease. (Invest Ophthalmol Vis Sci. 2001;42:305-312) T he contribution of the different retinal elements to the fast flicker ERG has not been determined precisely in the primate. Earlier studies indicated an outer retinal locus for the fast flicker ERG signals. 1-7 Baron, Boynton, and colleagues 6 -8 However, Donovan and Baron 2 found a disparity between intraretinal local ERG (LERG) responses and the corneal flicker response, which led them to wonder whether additional components might be contributing to the corneal flicker ERG beyond the intraretinal receptor potentials. Chang et al. 9 also suggest the possibility of postreceptoral contribution to the Sine-Wave flicker ERGs. It is known that the retinal response to Sine-Wave flicker stimuli is dominated by a component at the same temporal frequency as the stimulus, termed the fundamental component. However, under some conditions, a component is seen at twice the stimulus frequency (i.e., a second harmonic component). 10 -13 Current source density analysis 14 suggested that the fundamental component was dominated by photoreceptor activity, yet the second harmonic component originated from multiple retinal sources and included contributions from the middle and inner retina. A systems analytic approach in humans 12,13 also agreed with a model of the Sine-Wave flicker ERG that attributed the majority of the linear (or fundamental) component to photoreceptor-related processes, particularly at medium and high frequencies. Some clinical studies Previously, the authors studied the photopic fast flicker ERG using square Waves and photostrobe flashes 17 and found that the corneal response was virtually eliminated by aspartate or by the combination of DL-2-amino-4-phosphonobutyric acid (APB) 18 plus cis-2,3-piperidinedicarboxylic acid (PDA). 19 These drugs block transmission to the second-order neurons postsynaptic to cones. This study revisited the question of the origins of the primate flicker ERG and recorded Sine-Wave flicker responses from monkeys over a wide range of temporal frequencies on a photopic background before and after applying glutamate analogs. Particular attention was given to the nature of the fundamental frequency component
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primate photopic Sine Wave flicker erg vector modeling analysis of component origins using glutamate analogs
Investigative Ophthalmology & Visual Science, 2001Co-Authors: Mineo Kondo, Paul A SievingAbstract:Purpose To study how the photoreceptoral and postreceptoral ON- and OFF-components contribute to the photopic Sine-Wave flicker ERG in the monkey by isolating the components with glutamate analogs. Methods Monkey photopic flicker ERGs were elicited with Sine Wave stimuli (mean luminance, 2.66 log cd/m(2); 80% modulation depth, on a 40 cd/m(2) white background) and were recorded for stimulus frequencies of 4 Hz to 64 Hz, before and after intravitreal injection of DL-2-amino-4-phosphonobutyric acid (APB) and cis-2, 3-piperidinedicarboxylic acid (PDA) that block ON- and OFF-bipolar activity, respectively. The amplitude and phase of the fundamental component were analyzed. Results The flicker response amplitudes increased after APB, for frequencies of 6 Hz to 32 Hz. The further addition of PDA to isolate the photoreceptor component resulted in a relatively small residual response that decreased monotonically from 4 Hz to 32 Hz. The postsynaptic APB (ON-) and PDA (OFF-) sensitive components were isolated by subtraction and were characterized by amplitude and phase vectors. The ON- and OFF-components were larger than the initial control responses for stimuli of 8 Hz to 40 Hz. These two components had a frequency-dependent phase difference of 160 degrees to 230 degrees; normally, they interfere with each other and reduce their net contribution. The phase difference between ON- and OFF-components was nearly 180 degrees for a 10-Hz stimulus, and the phase cancellation caused a prominent dip in amplitude at this frequency. Conclusions These results indicate that postreceptoral ON- and OFF-components contribute substantially to the Sine-Wave flicker ERG, especially at higher stimulus frequencies. Because of phase cancellation, they mask each other in the net response in a frequency dependent fashion. The photoreceptor contribution is greater than the net postsynaptic component only for frequencies of approximately less than or equal to 10 Hz. These results can be summarized by a vector model that may be useful for interpreting changes resulting from retinal disease.
M J Ryan - One of the best experts on this subject based on the ideXlab platform.
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modeling of multileg Sine Wave inverters a geometric approach
IEEE Transactions on Industrial Electronics, 1999Co-Authors: M J Ryan, Robert D Lorenz, R W De DonckerAbstract:Three fundamental Sine-Wave inverter topologies are analyzed: two-leg (one-phase, two-wire); three-leg (three-phase, three-wire); and four-leg (three-phase, four-wire). The topologies are "full-bridge" voltage-source inverters with LC filters suitable for producing sinusoidal output voltages. The switching states and corresponding output voltage vectors produced by each inverter are identified and presented along with an analysis of the geometric arrangement of these voltage vectors. A pattern of characteristics is established whereby the "qd" modeling forms commonly used with three-leg inverters are extended to address the expanded capabilities of the four-leg inverter. A unique 4/spl times/4 decoupling transformation matrix is presented for the four-leg inverter that enables direct transformation between the four-degree-of-freedom (DOF) leg-modulation space of the inverter and its corresponding 3-DOF output-voltage space. This is shown to be directly analogous to the well-known "abc-qd" transformation developed for the three-leg inverter. Fully decoupled models for each inverter are presented.
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a high performance Sine Wave inverter controller with capacitor current feedback and back emf decoupling
Power Electronics Specialists Conference, 1995Co-Authors: M J Ryan, Robert D LorenzAbstract:This paper presents a state space approach to the problem of controlling a single phase PWM inverter with an LC output filter. These types of inverter are often used in uninterruptable power supplies (UPS) where a Sine Wave output voltage is to be maintained. Output voltage control is structured around an inner filter capacitor current loop where capacitor current is sensed via a single, small current transformer. This avoids the expense of multiple, active current sensors found in alternative designs. Performance of the capacitor current loop is enhanced with active decoupling of both the DC bus and the equivalent "back-EMF" of the output voltage. The output dynamic stiffness of the system is analyzed and plotted. Experimental results yield less than 0.5% total harmonic distortion (THD) at full load (8 kW), with transient response times of less than 200 /spl mu/s. >
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a high performance Sine Wave inverter controller with capacitor current feedback and back emf decoupling
Power Electronics Specialists Conference, 1995Co-Authors: M J Ryan, Robert D LorenzAbstract:This paper presents a state space approach to the problem of controlling a single phase PWM inverter with an LC output filter. These types of inverter are often used in uninterruptable power supplies (UPS) where a Sine Wave output voltage is to be maintained. Output voltage control is structured around an inner filter capacitor current loop where capacitor current is sensed via a single, small current transformer. This avoids the expense of multiple, active current sensors found in alternative designs. Performance of the capacitor current loop is enhanced with active decoupling of both the DC bus and the equivalent "back-EMF" of the output voltage. The output dynamic stiffness of the system is analyzed and plotted. Experimental results yield less than 0.5% total harmonic distortion (THD) at full load (8 kW), with transient response times of less than 200 /spl mu/s. >
Janez Grum - One of the best experts on this subject based on the ideXlab platform.
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optimisation of welding parameters in pulsed mig mag welding with width controlled Sine Wave current pulses part 1 determination of a general synergic equation and a normalised parametric diagram with a defined parametric welding range
International Journal of Materials & Product Technology, 2007Co-Authors: Danijel Langus, Viljem Kralj, Janez GrumAbstract:The paper treats synergic pulsed MIG/MAG welding with width-controlled Sine-Wave current pulses. Such a current-pulse Waveform will be obtained if a power source is controlled by thyristors integrated in a power circuit. In this case the pulse frequency is constant and the current-pulse power can be controlled by the delay time of the thyristor ignition. The paper focuses on a theoretical derivation of a general synergic equation of pulsed MIG/MAG welding with width-controlled Sine-Wave current pulses that relates a mean welding current with pulsed welding parameters. On this basis, a normalised parametric diagram with a defined parametric welding range can be defined and elaborated, which permits a further analysis of pulsed welding and optimisation of pulsed welding parameters.
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optimisation of welding parameters in pulsed mig mag welding with width controlled Sine Wave current pulses part 2 determination of an optimum material transfer through the arc and a control method
International Journal of Materials & Product Technology, 2007Co-Authors: Danijel Langus, Viljem Kralj, Janez GrumAbstract:The paper treats synergic pulsed MIG/MAG welding with width-controlled Sine-Wave current pulses. Such a pulse-current Waveform will be obtained if a power source is controlled by thyristors integrated in a power circuit with a constant pulse frequency. A momentary pulse current power, which is a product of a momentary value of current and voltage, can be controlled by the delay time of thyristor ignition. The paper focuses on an analysis and optimisation of the material transfer through the arc using a limiting criterion determined by an isoparametric equation. By means of the results obtained in the investigation, a parametric diagram with the optimum welding region for a chosen droplet volume transferred through the arc can be determined. The material transfer established will satisfy the criteria set to ensure a stable droplet transfer with no spatter and production of a sound weld. It turned out that the type of synergic welding device suggested for pulsed MIG7/MAG welding was suitable for the most exacting applications.
Robert D Lorenz - One of the best experts on this subject based on the ideXlab platform.
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modeling of multileg Sine Wave inverters a geometric approach
IEEE Transactions on Industrial Electronics, 1999Co-Authors: M J Ryan, Robert D Lorenz, R W De DonckerAbstract:Three fundamental Sine-Wave inverter topologies are analyzed: two-leg (one-phase, two-wire); three-leg (three-phase, three-wire); and four-leg (three-phase, four-wire). The topologies are "full-bridge" voltage-source inverters with LC filters suitable for producing sinusoidal output voltages. The switching states and corresponding output voltage vectors produced by each inverter are identified and presented along with an analysis of the geometric arrangement of these voltage vectors. A pattern of characteristics is established whereby the "qd" modeling forms commonly used with three-leg inverters are extended to address the expanded capabilities of the four-leg inverter. A unique 4/spl times/4 decoupling transformation matrix is presented for the four-leg inverter that enables direct transformation between the four-degree-of-freedom (DOF) leg-modulation space of the inverter and its corresponding 3-DOF output-voltage space. This is shown to be directly analogous to the well-known "abc-qd" transformation developed for the three-leg inverter. Fully decoupled models for each inverter are presented.
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a high performance Sine Wave inverter controller with capacitor current feedback and back emf decoupling
Power Electronics Specialists Conference, 1995Co-Authors: M J Ryan, Robert D LorenzAbstract:This paper presents a state space approach to the problem of controlling a single phase PWM inverter with an LC output filter. These types of inverter are often used in uninterruptable power supplies (UPS) where a Sine Wave output voltage is to be maintained. Output voltage control is structured around an inner filter capacitor current loop where capacitor current is sensed via a single, small current transformer. This avoids the expense of multiple, active current sensors found in alternative designs. Performance of the capacitor current loop is enhanced with active decoupling of both the DC bus and the equivalent "back-EMF" of the output voltage. The output dynamic stiffness of the system is analyzed and plotted. Experimental results yield less than 0.5% total harmonic distortion (THD) at full load (8 kW), with transient response times of less than 200 /spl mu/s. >
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a high performance Sine Wave inverter controller with capacitor current feedback and back emf decoupling
Power Electronics Specialists Conference, 1995Co-Authors: M J Ryan, Robert D LorenzAbstract:This paper presents a state space approach to the problem of controlling a single phase PWM inverter with an LC output filter. These types of inverter are often used in uninterruptable power supplies (UPS) where a Sine Wave output voltage is to be maintained. Output voltage control is structured around an inner filter capacitor current loop where capacitor current is sensed via a single, small current transformer. This avoids the expense of multiple, active current sensors found in alternative designs. Performance of the capacitor current loop is enhanced with active decoupling of both the DC bus and the equivalent "back-EMF" of the output voltage. The output dynamic stiffness of the system is analyzed and plotted. Experimental results yield less than 0.5% total harmonic distortion (THD) at full load (8 kW), with transient response times of less than 200 /spl mu/s. >
