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Papers by Siddhartha Duttagupta
IEEE Transactions on Biomedical Engineering, 2007
Wearable electrocardiogram (W-ECG) recorders are increasingly in use by people suffering from car... more Wearable electrocardiogram (W-ECG) recorders are increasingly in use by people suffering from cardiac abnormalities who also choose to lead an active lifestyle. The challenge presently is that the ECG signal is influenced by motion artifacts induced by body movement activity (BMA) of the wearer. The usual practice is to develop effective filtering algorithms which will eliminate artifacts. Instead, our goal is to detect the motion artifacts and classify the type of BMA from the ECG signal itself. We have recorded the ECG signals during specified BMAs, e.g., sitting still, walking, movements of arms and climbing stairs, etc. with a singlelead system. The collected ECG signal during BMA is presumed to be an additive mix of signals due to cardiac activities, motion artifacts and sensor noise. A particular class of BMA is characterized by applying eigen decomposition on the corresponding ECG data. The classification accuracies range from 70% to 98% for various class combinations of BMAs depending on their uniqueness based on this technique. The above classification is also useful for analysis of P and T waves in the presence of BMA.
Annals of Biomedical Engineering, 2008
Ambulatory ElectroCardioGram (ECG) analysis is adversely affected by motion artifacts induced due... more Ambulatory ElectroCardioGram (ECG) analysis is adversely affected by motion artifacts induced due to body movements. Knowledge of the extent of motion artifacts could facilitate better ECG analysis. In this paper, our purpose is to determine the impact of body movement kinematics on the extent of ECG motion artifact by defining a notion called impact signal. Two approaches have been adopted in this paper to validate our experiments. One of them involves measuring local acceleration using motion sensors at appropriate body positions, in conjunction with the ECG, while performing routine activities at different intensity levels. The other method consists of ECG acquisition during Treadmill testing at controlled speeds and fixed duration. Data has been acquired from both healthy subjects as well as patients with suspected cardio-vascular disorders. In case of patients, the treadmill tests were carried out under the supervision of a cardiologist. We demonstrate that the impact signal shows a proportional increase with the increasing activity levels. The measured accelerations obtained are also found to be well correlated with the impact signal. The impact analysis thus indicates the suitability of the proposed method for quantification of body movement kinematics from the ECG signal itself, even in the absence of any accelerometer sensors. Such quantification would also help in automatic documentation of patient activity levels, which could aid in better interpretation of ambulatory ECG.
IEEE Transactions on Biomedical Engineering, 2007
It has been shown by that the motion artifacts induced by body movement activity (BMA) in a singl... more It has been shown by that the motion artifacts induced by body movement activity (BMA) in a single-lead wearable electrocardiogram (ECG) signal recorder, while monitoring an ambulatory patient, can be detected and removed by using a principal component analysis (PCA)-based classification technique. However, this requires the ECG signal to be temporally segmented so that each segment comprises of artifacts due to a single type of body movement activity. In this paper, we propose a simple, recursively updated PCA-based technique to detect transitions wherever the type of body movement is changed.
Ambulatory ECG analysis is adversely affected by motion artifacts induced due to body movements. ... more Ambulatory ECG analysis is adversely affected by motion artifacts induced due to body movements. Knowledge of the extent of motion artifacts facilitates better ECG analysis. In [1], an unsupervised method using recursive principal component analysis (RPCA) was used to detect transitions between body movements. In this paper, we endeavour to quantify the impact of various types of body movements on the extent of ECG motion artifact using the RPCA error signal. For this purpose, acceleration data from different body parts i.e. arm(s), leg and waist, have been obtained using commercially available motion sensors, in conjunction with ECG signal, while carrying out routine body movement activities like climbing stairs, walking, twisting, and arm movements, at three different intensity levels: slow, medium and fast. The acceleration magnitudes and the RPCA error sequence are found to be well correlated, thus validating the body movement impact analysis, and also indicating the suitability of the method for quantification of body movement kinematics from the ECG signal itself in the absence of any accelerometer sensors.
Solid State Communications, 1995
Jpn. J. Appl. Phys. Vol. 37 (1998) pp. L 180L 183 Part 2, No. 2A, 1 February 1998 c 1998 Publica... more Jpn. J. Appl. Phys. Vol. 37 (1998) pp. L 180L 183 Part 2, No. 2A, 1 February 1998 c 1998 Publication Board, Japanese Journal of Applied Physics ... Photoluminescence and Electroluminescence in Polymer Mixture of Poly(alkylphenylacetylene) and Poly(diphenylacetylene) Derivatives
Physica Status Solidi (a), 1998
ABSTRACT
Physica Status Solidi (a), 1998
ABSTRACT We report the fabrication of nanocrastalline Si superlattices by phasma-assisted chemica... more ABSTRACT We report the fabrication of nanocrastalline Si superlattices by phasma-assisted chemical vapor deposition (PECVD) or magnetron sputtering of nanometer-thick amorphous Si (a-Si) layers followed by high-temperature recrystallization. The recrystallization is performed in two steps (rapid thermal pulse annealing and slow ramp-up furnace annealing) and has been monitored by Raman scattering. The fabrication technique is able to control the size and packing density of Si nanocrystals in the nc-Si/SiO2 superlattices. Preliminary results on the doping of Si nanocrystals are discussed. Room temperature photoluminescence with a quantum efficiency of 0.3% is demonstrated.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1995
ABSTRACT
IEEE Journal of Selected Topics in Quantum Electronics, 1995
Page 1. 1126 IEEE JOURNAL, OF SELECTED TOPICS LN QUANTUM ELECTRONICS, VOL 1, NO 4, DECEMBER 1995 ... more Page 1. 1126 IEEE JOURNAL, OF SELECTED TOPICS LN QUANTUM ELECTRONICS, VOL 1, NO 4, DECEMBER 1995 * ht-Emitting Porous Silicon: Materials cience, Properties, and Device Applications P. M. Fauchet, Senior ...
Thin Solid Films, 1997
By carefully controling the nanocrystallite surface passivation, it is possible to make light-emi... more By carefully controling the nanocrystallite surface passivation, it is possible to make light-emitting porous silicon essentially inert and to stabilize its photoluminescence. Using this material, which we call silicon-rich silicon oxide (SRSO), stable and efficient porous silicon lightemitting devices (LEDs) emitting in the visible have been manufactured. The material's optimization, device design, and device fabrication that have allowed us to achieve these goals are discussed. The electrical and optical properties of the LEDs are described and explained by a model for carrier transport and recombination. By changing the preparation and processing conditions and by doping the SRSO layer with impurities such as erbium, photoluminescence and electroluminescence at longer wavelengths have been demonstrated. q 1997 Elsevier Science S.A.
Acta Biomaterialia, 2008
The antimicrobial properties of silver and copper nanoparticles were investigated using Escherich... more The antimicrobial properties of silver and copper nanoparticles were investigated using Escherichia coli (four strains), Bacillus subtilis and Staphylococcus aureus (three strains). The average sizes of the silver and copper nanoparticles were 3 nm and 9 nm, respectively, as determined through transmission electron microscopy. Energy-dispersive X-ray spectra of silver and copper nanoparticles revealed that while silver was in its pure form, an oxide layer existed on the copper nanoparticles. The bactericidal effect of silver and copper nanoparticles were compared based on diameter of inhibition zone in disk diffusion tests and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of nanoparticles dispersed in batch cultures. Bacterial sensitivity to nanoparticles was found to vary depending on the microbial species. Disk diffusion studies with E. coli and S. aureus revealed greater effectiveness of the silver nanoparticles compared to the copper nanoparticles. B. subtilis depicted the highest sensitivity to nanoparticles compared to the other strains and was more adversely affected by the copper nanoparticles. Good correlation was observed between MIC and MBC (r 2 = 0.98) measured in liquid cultures. For copper nanoparticles a good negative correlation was observed between the inhibition zone observed in disk diffusion test and MIC/MBC determined based on liquid cultures with the various strains (r 2 = À0.75). Although strain-specific variation in MIC/MBC was negligible for S. aureus, some strain-specific variation was observed for E. coli.
IEEE Transactions on Biomedical Engineering, 2007
Wearable electrocardiogram (W-ECG) recorders are increasingly in use by people suffering from car... more Wearable electrocardiogram (W-ECG) recorders are increasingly in use by people suffering from cardiac abnormalities who also choose to lead an active lifestyle. The challenge presently is that the ECG signal is influenced by motion artifacts induced by body movement activity (BMA) of the wearer. The usual practice is to develop effective filtering algorithms which will eliminate artifacts. Instead, our goal is to detect the motion artifacts and classify the type of BMA from the ECG signal itself. We have recorded the ECG signals during specified BMAs, e.g., sitting still, walking, movements of arms and climbing stairs, etc. with a singlelead system. The collected ECG signal during BMA is presumed to be an additive mix of signals due to cardiac activities, motion artifacts and sensor noise. A particular class of BMA is characterized by applying eigen decomposition on the corresponding ECG data. The classification accuracies range from 70% to 98% for various class combinations of BMAs depending on their uniqueness based on this technique. The above classification is also useful for analysis of P and T waves in the presence of BMA.
Annals of Biomedical Engineering, 2008
Ambulatory ElectroCardioGram (ECG) analysis is adversely affected by motion artifacts induced due... more Ambulatory ElectroCardioGram (ECG) analysis is adversely affected by motion artifacts induced due to body movements. Knowledge of the extent of motion artifacts could facilitate better ECG analysis. In this paper, our purpose is to determine the impact of body movement kinematics on the extent of ECG motion artifact by defining a notion called impact signal. Two approaches have been adopted in this paper to validate our experiments. One of them involves measuring local acceleration using motion sensors at appropriate body positions, in conjunction with the ECG, while performing routine activities at different intensity levels. The other method consists of ECG acquisition during Treadmill testing at controlled speeds and fixed duration. Data has been acquired from both healthy subjects as well as patients with suspected cardio-vascular disorders. In case of patients, the treadmill tests were carried out under the supervision of a cardiologist. We demonstrate that the impact signal shows a proportional increase with the increasing activity levels. The measured accelerations obtained are also found to be well correlated with the impact signal. The impact analysis thus indicates the suitability of the proposed method for quantification of body movement kinematics from the ECG signal itself, even in the absence of any accelerometer sensors. Such quantification would also help in automatic documentation of patient activity levels, which could aid in better interpretation of ambulatory ECG.
IEEE Transactions on Biomedical Engineering, 2007
It has been shown by that the motion artifacts induced by body movement activity (BMA) in a singl... more It has been shown by that the motion artifacts induced by body movement activity (BMA) in a single-lead wearable electrocardiogram (ECG) signal recorder, while monitoring an ambulatory patient, can be detected and removed by using a principal component analysis (PCA)-based classification technique. However, this requires the ECG signal to be temporally segmented so that each segment comprises of artifacts due to a single type of body movement activity. In this paper, we propose a simple, recursively updated PCA-based technique to detect transitions wherever the type of body movement is changed.
Ambulatory ECG analysis is adversely affected by motion artifacts induced due to body movements. ... more Ambulatory ECG analysis is adversely affected by motion artifacts induced due to body movements. Knowledge of the extent of motion artifacts facilitates better ECG analysis. In [1], an unsupervised method using recursive principal component analysis (RPCA) was used to detect transitions between body movements. In this paper, we endeavour to quantify the impact of various types of body movements on the extent of ECG motion artifact using the RPCA error signal. For this purpose, acceleration data from different body parts i.e. arm(s), leg and waist, have been obtained using commercially available motion sensors, in conjunction with ECG signal, while carrying out routine body movement activities like climbing stairs, walking, twisting, and arm movements, at three different intensity levels: slow, medium and fast. The acceleration magnitudes and the RPCA error sequence are found to be well correlated, thus validating the body movement impact analysis, and also indicating the suitability of the method for quantification of body movement kinematics from the ECG signal itself in the absence of any accelerometer sensors.
Solid State Communications, 1995
Jpn. J. Appl. Phys. Vol. 37 (1998) pp. L 180L 183 Part 2, No. 2A, 1 February 1998 c 1998 Publica... more Jpn. J. Appl. Phys. Vol. 37 (1998) pp. L 180L 183 Part 2, No. 2A, 1 February 1998 c 1998 Publication Board, Japanese Journal of Applied Physics ... Photoluminescence and Electroluminescence in Polymer Mixture of Poly(alkylphenylacetylene) and Poly(diphenylacetylene) Derivatives
Physica Status Solidi (a), 1998
ABSTRACT
Physica Status Solidi (a), 1998
ABSTRACT We report the fabrication of nanocrastalline Si superlattices by phasma-assisted chemica... more ABSTRACT We report the fabrication of nanocrastalline Si superlattices by phasma-assisted chemical vapor deposition (PECVD) or magnetron sputtering of nanometer-thick amorphous Si (a-Si) layers followed by high-temperature recrystallization. The recrystallization is performed in two steps (rapid thermal pulse annealing and slow ramp-up furnace annealing) and has been monitored by Raman scattering. The fabrication technique is able to control the size and packing density of Si nanocrystals in the nc-Si/SiO2 superlattices. Preliminary results on the doping of Si nanocrystals are discussed. Room temperature photoluminescence with a quantum efficiency of 0.3% is demonstrated.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1995
ABSTRACT
IEEE Journal of Selected Topics in Quantum Electronics, 1995
Page 1. 1126 IEEE JOURNAL, OF SELECTED TOPICS LN QUANTUM ELECTRONICS, VOL 1, NO 4, DECEMBER 1995 ... more Page 1. 1126 IEEE JOURNAL, OF SELECTED TOPICS LN QUANTUM ELECTRONICS, VOL 1, NO 4, DECEMBER 1995 * ht-Emitting Porous Silicon: Materials cience, Properties, and Device Applications P. M. Fauchet, Senior ...
Thin Solid Films, 1997
By carefully controling the nanocrystallite surface passivation, it is possible to make light-emi... more By carefully controling the nanocrystallite surface passivation, it is possible to make light-emitting porous silicon essentially inert and to stabilize its photoluminescence. Using this material, which we call silicon-rich silicon oxide (SRSO), stable and efficient porous silicon lightemitting devices (LEDs) emitting in the visible have been manufactured. The material's optimization, device design, and device fabrication that have allowed us to achieve these goals are discussed. The electrical and optical properties of the LEDs are described and explained by a model for carrier transport and recombination. By changing the preparation and processing conditions and by doping the SRSO layer with impurities such as erbium, photoluminescence and electroluminescence at longer wavelengths have been demonstrated. q 1997 Elsevier Science S.A.
Acta Biomaterialia, 2008
The antimicrobial properties of silver and copper nanoparticles were investigated using Escherich... more The antimicrobial properties of silver and copper nanoparticles were investigated using Escherichia coli (four strains), Bacillus subtilis and Staphylococcus aureus (three strains). The average sizes of the silver and copper nanoparticles were 3 nm and 9 nm, respectively, as determined through transmission electron microscopy. Energy-dispersive X-ray spectra of silver and copper nanoparticles revealed that while silver was in its pure form, an oxide layer existed on the copper nanoparticles. The bactericidal effect of silver and copper nanoparticles were compared based on diameter of inhibition zone in disk diffusion tests and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of nanoparticles dispersed in batch cultures. Bacterial sensitivity to nanoparticles was found to vary depending on the microbial species. Disk diffusion studies with E. coli and S. aureus revealed greater effectiveness of the silver nanoparticles compared to the copper nanoparticles. B. subtilis depicted the highest sensitivity to nanoparticles compared to the other strains and was more adversely affected by the copper nanoparticles. Good correlation was observed between MIC and MBC (r 2 = 0.98) measured in liquid cultures. For copper nanoparticles a good negative correlation was observed between the inhibition zone observed in disk diffusion test and MIC/MBC determined based on liquid cultures with the various strains (r 2 = À0.75). Although strain-specific variation in MIC/MBC was negligible for S. aureus, some strain-specific variation was observed for E. coli.