TY  - JOUR
AU  - Kalauzi, Aleksandar
AU  - Matić, Zoran
AU  - Platiša, Mirjana M.
AU  - Bojić, Tijana
PY  - 2023
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10708
AB  - Due to the fact that respiratory breath-to-breath and cardiac intervals between two successive R peaks (BBI and RRI, respectively) are not temporally concurrent, in a previous paper, we proposed a method to calculate both the integer and non-integer parts of the pulse respiration quotient (PRQ = BBI/RRI = PRQint + b1 + b2), b1 and b2 being parts of the border RRIs for each BBI. In this work, we study the correlations between BBI and PRQ, as well as those between BBI and mean RRI within each BBI (mRRI), on a group of twenty subjects in four conditions: in supine and standing positions, in combination with spontaneous and slow breathing. Results show that the BBI vs. PRQ correlations are positive; whereas the breathing regime had little or no effect on the linear regression slopes, body posture did. Two types of scatter plots were obtained with the BBI vs. mRRI correlations: one showed points aggregated around the concurrent PRQint lines, while the other showed randomly distributed points. Five out of six of the proposed aggregation measures confirmed the existence of these two cardio-respiratory coupling regimes. We also used b1 to study the positions of R pulses relative to the respiration onsets and showed that they were more synchronous with sympathetic activation. Overall, this method should be used in different pathological states.
T2  - Bioengineering
T1  - Two Operational Modes of Cardio-Respiratory Coupling Revealed by Pulse-Respiration Quotient
VL  - 10
IS  - 2
SP  - 180
DO  - 10.3390/bioengineering10020180
ER  - 

@article{
author = "Kalauzi, Aleksandar and Matić, Zoran and Platiša, Mirjana M. and Bojić, Tijana",
year = "2023",
abstract = "Due to the fact that respiratory breath-to-breath and cardiac intervals between two successive R peaks (BBI and RRI, respectively) are not temporally concurrent, in a previous paper, we proposed a method to calculate both the integer and non-integer parts of the pulse respiration quotient (PRQ = BBI/RRI = PRQint + b1 + b2), b1 and b2 being parts of the border RRIs for each BBI. In this work, we study the correlations between BBI and PRQ, as well as those between BBI and mean RRI within each BBI (mRRI), on a group of twenty subjects in four conditions: in supine and standing positions, in combination with spontaneous and slow breathing. Results show that the BBI vs. PRQ correlations are positive; whereas the breathing regime had little or no effect on the linear regression slopes, body posture did. Two types of scatter plots were obtained with the BBI vs. mRRI correlations: one showed points aggregated around the concurrent PRQint lines, while the other showed randomly distributed points. Five out of six of the proposed aggregation measures confirmed the existence of these two cardio-respiratory coupling regimes. We also used b1 to study the positions of R pulses relative to the respiration onsets and showed that they were more synchronous with sympathetic activation. Overall, this method should be used in different pathological states.",
journal = "Bioengineering",
title = "Two Operational Modes of Cardio-Respiratory Coupling Revealed by Pulse-Respiration Quotient",
volume = "10",
number = "2",
pages = "180",
doi = "10.3390/bioengineering10020180"
}

Kalauzi, A., Matić, Z., Platiša, M. M.,& Bojić, T.. (2023). Two Operational Modes of Cardio-Respiratory Coupling Revealed by Pulse-Respiration Quotient. in Bioengineering, 10(2), 180.
https://doi.org/10.3390/bioengineering10020180

Kalauzi A, Matić Z, Platiša MM, Bojić T. Two Operational Modes of Cardio-Respiratory Coupling Revealed by Pulse-Respiration Quotient. in Bioengineering. 2023;10(2):180.
doi:10.3390/bioengineering10020180 .

Kalauzi, Aleksandar, Matić, Zoran, Platiša, Mirjana M., Bojić, Tijana, "Two Operational Modes of Cardio-Respiratory Coupling Revealed by Pulse-Respiration Quotient" in Bioengineering, 10, no. 2 (2023):180,
https://doi.org/10.3390/bioengineering10020180 . .

TY  - JOUR
AU  - Kalauzi, Aleksandar
AU  - Matić, Zoran
AU  - Bojić, Tijana
AU  - Platiša, Mirjana M.
PY  - 2023
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10507
AB  - ObjectivesIn order to reveal their structure, Poincaré plots (PP) of electrocardiogram (ECG) RR intervals (RRI) were studied as linear edge planar directed graphs, obtained by connecting all their sequential points. We were also aimed at studying their graph complexity properties.MethodsRRI signals were subjected to a series of different window length (WL) Moving Average Low Pass (MALP) filters. For each filtered graph, four standard PP descriptors: Pearson’s coefficient, SD1, SD2, and SD2/SD1 were calculated, as well as four new graph complexity measures: mean angle between adjacent graph edges; mean number of edge crossings; directional complexity and directional entropy. This approach was applied to signals of twenty young healthy subjects, recorded in four experimental conditions – combination of two body postures (supine and standing) and two breathing regimes (spontaneous and slow 0.1 Hz).ResultsWe found that PP graphs consist of two superimposed components: one originating from Respiratory Sinus Arrhythmia (RSA) oscillations, the other from slow variations (SV) of the RRI time series. This result was further corroborated by observing the transformation of a PP cloud shape occurring in filtered graphs. When applied to subjects, the outcome was that three measures significantly differentiated the two breathing regimes in the RSA region of the WL domain, while four other measures were able to differentiate two body postures in the SV WL region.DiscussionAfter obtaining these results in healthy, we expect to successfully apply this approach to patients suffering from different pathological conditions.
T2  - Biomedical Signal Processing and Control
T1  - Structure of Poincaré plots revealed by their graph analysis and low pass filtering of the RRI time series
VL  - 80
SP  - 104352
DO  - 10.1016/j.bspc.2022.104352
ER  - 

@article{
author = "Kalauzi, Aleksandar and Matić, Zoran and Bojić, Tijana and Platiša, Mirjana M.",
year = "2023",
abstract = "ObjectivesIn order to reveal their structure, Poincaré plots (PP) of electrocardiogram (ECG) RR intervals (RRI) were studied as linear edge planar directed graphs, obtained by connecting all their sequential points. We were also aimed at studying their graph complexity properties.MethodsRRI signals were subjected to a series of different window length (WL) Moving Average Low Pass (MALP) filters. For each filtered graph, four standard PP descriptors: Pearson’s coefficient, SD1, SD2, and SD2/SD1 were calculated, as well as four new graph complexity measures: mean angle between adjacent graph edges; mean number of edge crossings; directional complexity and directional entropy. This approach was applied to signals of twenty young healthy subjects, recorded in four experimental conditions – combination of two body postures (supine and standing) and two breathing regimes (spontaneous and slow 0.1 Hz).ResultsWe found that PP graphs consist of two superimposed components: one originating from Respiratory Sinus Arrhythmia (RSA) oscillations, the other from slow variations (SV) of the RRI time series. This result was further corroborated by observing the transformation of a PP cloud shape occurring in filtered graphs. When applied to subjects, the outcome was that three measures significantly differentiated the two breathing regimes in the RSA region of the WL domain, while four other measures were able to differentiate two body postures in the SV WL region.DiscussionAfter obtaining these results in healthy, we expect to successfully apply this approach to patients suffering from different pathological conditions.",
journal = "Biomedical Signal Processing and Control",
title = "Structure of Poincaré plots revealed by their graph analysis and low pass filtering of the RRI time series",
volume = "80",
pages = "104352",
doi = "10.1016/j.bspc.2022.104352"
}

Kalauzi, A., Matić, Z., Bojić, T.,& Platiša, M. M.. (2023). Structure of Poincaré plots revealed by their graph analysis and low pass filtering of the RRI time series. in Biomedical Signal Processing and Control, 80, 104352.
https://doi.org/10.1016/j.bspc.2022.104352

Kalauzi A, Matić Z, Bojić T, Platiša MM. Structure of Poincaré plots revealed by their graph analysis and low pass filtering of the RRI time series. in Biomedical Signal Processing and Control. 2023;80:104352.
doi:10.1016/j.bspc.2022.104352 .

Kalauzi, Aleksandar, Matić, Zoran, Bojić, Tijana, Platiša, Mirjana M., "Structure of Poincaré plots revealed by their graph analysis and low pass filtering of the RRI time series" in Biomedical Signal Processing and Control, 80 (2023):104352,
https://doi.org/10.1016/j.bspc.2022.104352 . .

TY  - CONF
AU  - Matić, Zoran
AU  - Kalauzi, Aleksandar
AU  - Platiša, Mirjana M.
AU  - Bojić, Tijana
PY  - 2022
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10513
AB  - It has become common in research with detrended fluctuation analysis (DFA) to use slopes of regression lines (α1 and α2) and their ratio as measures of fractal properties of dynamical processes such as physiological rhythm fluctuations. In this study, instead of the ratio (α1/α2) in DFA of ECG RR intervals and respiratory signals, we propose the use of a new measure: the inter-fractal angle (θ) - angle that DFA regression lines form between each other. Methods. Angle θ was obtained by means of graphical-analytical calculation. Using one way-Anova test, sensitivity of θ on the influence of slow breathing and orthostasis was compared in respect to ratio α1/α2. Results. Comparisons revealed that changes of (θ) were statistically more significant than changes of αl/α2. Conclusion. Inter-fractal angle is an elegant new measure of DFA that is more sensitive to perturbations such as changes in body posture and breathing regime than α1/α2.
C3  - 2022 12th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO)
T1  - Sensitivity Estimations in Favor of Using Inter-fractal Angle in Detrended Fluctuation Analysis
SP  - 1
EP  - 2
DO  - 10.1109/ESGCO55423.2022.9931387
ER  - 

@conference{
author = "Matić, Zoran and Kalauzi, Aleksandar and Platiša, Mirjana M. and Bojić, Tijana",
year = "2022",
abstract = "It has become common in research with detrended fluctuation analysis (DFA) to use slopes of regression lines (α1 and α2) and their ratio as measures of fractal properties of dynamical processes such as physiological rhythm fluctuations. In this study, instead of the ratio (α1/α2) in DFA of ECG RR intervals and respiratory signals, we propose the use of a new measure: the inter-fractal angle (θ) - angle that DFA regression lines form between each other. Methods. Angle θ was obtained by means of graphical-analytical calculation. Using one way-Anova test, sensitivity of θ on the influence of slow breathing and orthostasis was compared in respect to ratio α1/α2. Results. Comparisons revealed that changes of (θ) were statistically more significant than changes of αl/α2. Conclusion. Inter-fractal angle is an elegant new measure of DFA that is more sensitive to perturbations such as changes in body posture and breathing regime than α1/α2.",
journal = "2022 12th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO)",
title = "Sensitivity Estimations in Favor of Using Inter-fractal Angle in Detrended Fluctuation Analysis",
pages = "1-2",
doi = "10.1109/ESGCO55423.2022.9931387"
}

Matić, Z., Kalauzi, A., Platiša, M. M.,& Bojić, T.. (2022). Sensitivity Estimations in Favor of Using Inter-fractal Angle in Detrended Fluctuation Analysis. in 2022 12th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO), 1-2.
https://doi.org/10.1109/ESGCO55423.2022.9931387

Matić Z, Kalauzi A, Platiša MM, Bojić T. Sensitivity Estimations in Favor of Using Inter-fractal Angle in Detrended Fluctuation Analysis. in 2022 12th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO). 2022;:1-2.
doi:10.1109/ESGCO55423.2022.9931387 .

Matić, Zoran, Kalauzi, Aleksandar, Platiša, Mirjana M., Bojić, Tijana, "Sensitivity Estimations in Favor of Using Inter-fractal Angle in Detrended Fluctuation Analysis" in 2022 12th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO) (2022):1-2,
https://doi.org/10.1109/ESGCO55423.2022.9931387 . .

TY  - JOUR
AU  - Matić, Zoran
AU  - Kalauzi, Aleksandar
AU  - Moser, Maximilian
AU  - Platiša, Mirjana M.
AU  - Lazarević, Mihailo
AU  - Bojić, Tijana
PY  - 2022
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10599
AB  - In this research we explored the (homeo)dynamic character of cardiorespiratory coupling (CRC) under the influence of different body posture and breathing regimes. Our tool for it was the pulse respiration quotient (PRQ), representing the number of heartbeat intervals per breathing cycle. We obtained non-integer PRQ values using our advanced Matlab® algorithm and applied it on the signals of 20 healthy subjects in four conditions: supine position with spontaneous breathing (Supin), standing with spontaneous breathing (Stand), supine position with slow (0.1 Hz) breathing (Supin01) and standing with slow (0.1 Hz) breathing (Stand01).Main results: Linear features of CRC (in PRQ signals) were dynamically very sensitive to posture and breathing rhythm perturbations. There are obvious increases in PRQ mean level and variability under the separated and joined influence of orthostasis and slow (0.1 Hz) breathing. This increase was most pronounced in Stand01 as the state of joint influences. Importantly, PRQ dynamic modification showed greater sensitivity to body posture and breathing regime changes than mean value and standard deviation of heart rhythm and breathing rhythm. In addition, as a consequence of prolonged supine position, we noticed the tendency to integer quantization of PRQ (especially after 14 min), in which the most common quantization number was 4:1 (demonstrated in other research reports as well). In orthostasis and slow breathing, quantization can also be observed, but shifted to other values. We postulate that these results manifest resonance effects induced by coupling patterns from sympathetic and parasympathetic adjustments (with the second as dominant factor).Significance: Our research confirms that cardiorespiratory coupling adaptability could be profoundly explored by precisely calculated PRQ parameter since cardiorespiratory regulation in healthy subjects is characterized by a high level of autonomic adaptability (responsiveness) to posture and breathing regime, although comparisons with pathological states has yet to be performed. We found Stand01 to be the most provoking state for the dynamic modification of PRQ (cardiorespiratory inducement). As such, Stand01 has the potential of using for PRQ tuning by conditioning the cardiorespiratory autonomic neural networks, e.g., in the cases where PRQ is disturbed by environmental (i.e., microgravity) or pathologic conditions.
T2  - Frontiers in Physiology
T1  - Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime
VL  - 13
DO  - 10.3389/fphys.2022.946613
ER  - 

@article{
author = "Matić, Zoran and Kalauzi, Aleksandar and Moser, Maximilian and Platiša, Mirjana M. and Lazarević, Mihailo and Bojić, Tijana",
year = "2022",
abstract = "In this research we explored the (homeo)dynamic character of cardiorespiratory coupling (CRC) under the influence of different body posture and breathing regimes. Our tool for it was the pulse respiration quotient (PRQ), representing the number of heartbeat intervals per breathing cycle. We obtained non-integer PRQ values using our advanced Matlab® algorithm and applied it on the signals of 20 healthy subjects in four conditions: supine position with spontaneous breathing (Supin), standing with spontaneous breathing (Stand), supine position with slow (0.1 Hz) breathing (Supin01) and standing with slow (0.1 Hz) breathing (Stand01).Main results: Linear features of CRC (in PRQ signals) were dynamically very sensitive to posture and breathing rhythm perturbations. There are obvious increases in PRQ mean level and variability under the separated and joined influence of orthostasis and slow (0.1 Hz) breathing. This increase was most pronounced in Stand01 as the state of joint influences. Importantly, PRQ dynamic modification showed greater sensitivity to body posture and breathing regime changes than mean value and standard deviation of heart rhythm and breathing rhythm. In addition, as a consequence of prolonged supine position, we noticed the tendency to integer quantization of PRQ (especially after 14 min), in which the most common quantization number was 4:1 (demonstrated in other research reports as well). In orthostasis and slow breathing, quantization can also be observed, but shifted to other values. We postulate that these results manifest resonance effects induced by coupling patterns from sympathetic and parasympathetic adjustments (with the second as dominant factor).Significance: Our research confirms that cardiorespiratory coupling adaptability could be profoundly explored by precisely calculated PRQ parameter since cardiorespiratory regulation in healthy subjects is characterized by a high level of autonomic adaptability (responsiveness) to posture and breathing regime, although comparisons with pathological states has yet to be performed. We found Stand01 to be the most provoking state for the dynamic modification of PRQ (cardiorespiratory inducement). As such, Stand01 has the potential of using for PRQ tuning by conditioning the cardiorespiratory autonomic neural networks, e.g., in the cases where PRQ is disturbed by environmental (i.e., microgravity) or pathologic conditions.",
journal = "Frontiers in Physiology",
title = "Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime",
volume = "13",
doi = "10.3389/fphys.2022.946613"
}

Matić, Z., Kalauzi, A., Moser, M., Platiša, M. M., Lazarević, M.,& Bojić, T.. (2022). Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime. in Frontiers in Physiology, 13.
https://doi.org/10.3389/fphys.2022.946613

Matić Z, Kalauzi A, Moser M, Platiša MM, Lazarević M, Bojić T. Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime. in Frontiers in Physiology. 2022;13.
doi:10.3389/fphys.2022.946613 .

Matić, Zoran, Kalauzi, Aleksandar, Moser, Maximilian, Platiša, Mirjana M., Lazarević, Mihailo, Bojić, Tijana, "Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime" in Frontiers in Physiology, 13 (2022),
https://doi.org/10.3389/fphys.2022.946613 . .

TY  - JOUR
AU  - Matić, Zoran
AU  - Platiša, Mirjana M.
AU  - Kalauzi, Aleksandar
AU  - Bojić, Tijana
PY  - 2020
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8848
AB  - Objective: We explored the physiological background of the non-linear operating mode of cardiorespiratory oscillators as the fundamental question of cardiorespiratory homeodynamics and as a prerequisite for the understanding of neurocardiovascular diseases. We investigated 20 healthy human subjects for changes using electrocardiac RR interval (RRI) and respiratory signal (Resp) Detrended Fluctuation Analysis (DFA, α1RRI, α2RRI, α1Resp, α2Resp), Multiple Scaling Entropy (MSERRI1−4, MSERRI5−10, MSEResp1−4, MSEResp5−10), spectral coherence (CohRRI−Resp), cross DFA (ρ1 and ρ2) and cross MSE (XMSE1−4 and XMSE5−10) indices in four physiological conditions: supine with spontaneous breathing, standing with spontaneous breathing, supine with 0.1 Hz breathing and standing with 0.1 Hz breathing. Main results: Standing is primarily characterized by the change of RRI parameters, insensitivity to change with respiratory parameters, decrease of CohRRI−Resp and insensitivity to change of in ρ1, ρ2, XMSE1−4, and XMSE5−10. Slow breathing in supine position was characterized by the change of the linear and non-linear parameters of both signals, reflecting the dominant vagal RRI modulation and the impact of slow 0.1 Hz breathing on Resp parameters. CohRRI−Resp did not change with respect to supine position, while ρ1 increased. Slow breathing in standing reflected the qualitatively specific state of autonomic regulation with striking impact on both cardiac and respiratory parameters, with specific patterns of cardiorespiratory coupling. Significance: Our results show that cardiac and respiratory short term and long term complexity parameters have different, state dependent patterns. Sympathovagal non-linear interactions are dependent on the pattern of their activation, having different scaling properties when individually activated with respect to the state of their joint activation. All investigated states induced a change of α1 vs. α2 relationship, which can be accurately expressed by the proposed measure—inter-fractal angle θ. Short scale (α1 vs. MSE1−4) and long scale (α2 vs. MSE5−10) complexity measures had reciprocal interrelation in standing with 0.1 Hz breathing, with specific cardiorespiratory coupling pattern (ρ1 vs. XMSE1−4). These results support the hypothesis of hierarchical organization of cardiorespiratory complexity mechanisms and their recruitment in ascendant manner with respect to the increase of behavioral challenge complexity. Specific and comprehensive cardiorespiratory regulation in standing with 0.1 Hz breathing suggests this state as the potentially most beneficial maneuver for cardiorespiratory conditioning. © Copyright © 2020 Matić, Platiša, Kalauzi and Bojić.
T2  - Frontiers in Physiology
T1  - Slow 0.1 Hz Breathing and Body Posture Induced Perturbations of RRI and Respiratory Signal Complexity and Cardiorespiratory Coupling
VL  - 11
SP  - 24
DO  - 10.3389/fphys.2020.00024
ER  - 

@article{
author = "Matić, Zoran and Platiša, Mirjana M. and Kalauzi, Aleksandar and Bojić, Tijana",
year = "2020",
abstract = "Objective: We explored the physiological background of the non-linear operating mode of cardiorespiratory oscillators as the fundamental question of cardiorespiratory homeodynamics and as a prerequisite for the understanding of neurocardiovascular diseases. We investigated 20 healthy human subjects for changes using electrocardiac RR interval (RRI) and respiratory signal (Resp) Detrended Fluctuation Analysis (DFA, α1RRI, α2RRI, α1Resp, α2Resp), Multiple Scaling Entropy (MSERRI1−4, MSERRI5−10, MSEResp1−4, MSEResp5−10), spectral coherence (CohRRI−Resp), cross DFA (ρ1 and ρ2) and cross MSE (XMSE1−4 and XMSE5−10) indices in four physiological conditions: supine with spontaneous breathing, standing with spontaneous breathing, supine with 0.1 Hz breathing and standing with 0.1 Hz breathing. Main results: Standing is primarily characterized by the change of RRI parameters, insensitivity to change with respiratory parameters, decrease of CohRRI−Resp and insensitivity to change of in ρ1, ρ2, XMSE1−4, and XMSE5−10. Slow breathing in supine position was characterized by the change of the linear and non-linear parameters of both signals, reflecting the dominant vagal RRI modulation and the impact of slow 0.1 Hz breathing on Resp parameters. CohRRI−Resp did not change with respect to supine position, while ρ1 increased. Slow breathing in standing reflected the qualitatively specific state of autonomic regulation with striking impact on both cardiac and respiratory parameters, with specific patterns of cardiorespiratory coupling. Significance: Our results show that cardiac and respiratory short term and long term complexity parameters have different, state dependent patterns. Sympathovagal non-linear interactions are dependent on the pattern of their activation, having different scaling properties when individually activated with respect to the state of their joint activation. All investigated states induced a change of α1 vs. α2 relationship, which can be accurately expressed by the proposed measure—inter-fractal angle θ. Short scale (α1 vs. MSE1−4) and long scale (α2 vs. MSE5−10) complexity measures had reciprocal interrelation in standing with 0.1 Hz breathing, with specific cardiorespiratory coupling pattern (ρ1 vs. XMSE1−4). These results support the hypothesis of hierarchical organization of cardiorespiratory complexity mechanisms and their recruitment in ascendant manner with respect to the increase of behavioral challenge complexity. Specific and comprehensive cardiorespiratory regulation in standing with 0.1 Hz breathing suggests this state as the potentially most beneficial maneuver for cardiorespiratory conditioning. © Copyright © 2020 Matić, Platiša, Kalauzi and Bojić.",
journal = "Frontiers in Physiology",
title = "Slow 0.1 Hz Breathing and Body Posture Induced Perturbations of RRI and Respiratory Signal Complexity and Cardiorespiratory Coupling",
volume = "11",
pages = "24",
doi = "10.3389/fphys.2020.00024"
}

Matić, Z., Platiša, M. M., Kalauzi, A.,& Bojić, T.. (2020). Slow 0.1 Hz Breathing and Body Posture Induced Perturbations of RRI and Respiratory Signal Complexity and Cardiorespiratory Coupling. in Frontiers in Physiology, 11, 24.
https://doi.org/10.3389/fphys.2020.00024

Matić Z, Platiša MM, Kalauzi A, Bojić T. Slow 0.1 Hz Breathing and Body Posture Induced Perturbations of RRI and Respiratory Signal Complexity and Cardiorespiratory Coupling. in Frontiers in Physiology. 2020;11:24.
doi:10.3389/fphys.2020.00024 .

Matić, Zoran, Platiša, Mirjana M., Kalauzi, Aleksandar, Bojić, Tijana, "Slow 0.1 Hz Breathing and Body Posture Induced Perturbations of RRI and Respiratory Signal Complexity and Cardiorespiratory Coupling" in Frontiers in Physiology, 11 (2020):24,
https://doi.org/10.3389/fphys.2020.00024 . .

TY  - JOUR
AU  - Platiša, Mirjana M.
AU  - Bojić, Tijana
AU  - Mazić, Sanja D.
AU  - Kalauzi, Aleksandar
PY  - 2019
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8413
AB  - Background Recently we proposed a new method called generalized Poincare´ plot (gPp) analysis which gave a new insight into the pattern of neurocaridac control. In this study we examined potential of gPp method to reveal changes in cardiac neural control in young athletes during three conditions: supine rest, running and relaxation, with respect to untrained subjects. Methods This method is based on the quantification of Pearson's correlation coefficients r(j, k), between symmetrical (j = k) and asymmetrical summed j previous and k following RR intervals up to the 100th order (j,k.100). Results Differences between groups were obtained at all levels of this analysis. The main result is the significant difference of NAI, normalized index of asymmetry, between groups in running, which was originated in different positions of local maxima of r(j, k). Compared with untrained subjects, these findings indicate modified neural control and altered intrinsic heart rate behavior in athletes which are related to some kind of memory mechanism between RR intervals. Conclusion Obtained results provide great potential of gPp method analysis in the recognition of changes in neurocardiac control in healthy subjects. Further studies are needed for identification of altered cardiac regulatory mechanisms whose background may be useful in the evaluation of genesis of athletes neurocardiovascular pathology. © 2019 Platiša et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
T2  - PLOS One
T1  - Generalized Poincaré plots analysis of heart period dynamics in different physiological conditions: Trained vs. untrained men
VL  - 14
IS  - 7
SP  - e0219281
DO  - 10.1371/journal.pone.0219281
ER  - 

@article{
author = "Platiša, Mirjana M. and Bojić, Tijana and Mazić, Sanja D. and Kalauzi, Aleksandar",
year = "2019",
abstract = "Background Recently we proposed a new method called generalized Poincare´ plot (gPp) analysis which gave a new insight into the pattern of neurocaridac control. In this study we examined potential of gPp method to reveal changes in cardiac neural control in young athletes during three conditions: supine rest, running and relaxation, with respect to untrained subjects. Methods This method is based on the quantification of Pearson's correlation coefficients r(j, k), between symmetrical (j = k) and asymmetrical summed j previous and k following RR intervals up to the 100th order (j,k.100). Results Differences between groups were obtained at all levels of this analysis. The main result is the significant difference of NAI, normalized index of asymmetry, between groups in running, which was originated in different positions of local maxima of r(j, k). Compared with untrained subjects, these findings indicate modified neural control and altered intrinsic heart rate behavior in athletes which are related to some kind of memory mechanism between RR intervals. Conclusion Obtained results provide great potential of gPp method analysis in the recognition of changes in neurocardiac control in healthy subjects. Further studies are needed for identification of altered cardiac regulatory mechanisms whose background may be useful in the evaluation of genesis of athletes neurocardiovascular pathology. © 2019 Platiša et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.",
journal = "PLOS One",
title = "Generalized Poincaré plots analysis of heart period dynamics in different physiological conditions: Trained vs. untrained men",
volume = "14",
number = "7",
pages = "e0219281",
doi = "10.1371/journal.pone.0219281"
}

Platiša, M. M., Bojić, T., Mazić, S. D.,& Kalauzi, A.. (2019). Generalized Poincaré plots analysis of heart period dynamics in different physiological conditions: Trained vs. untrained men. in PLOS One, 14(7), e0219281.
https://doi.org/10.1371/journal.pone.0219281

Platiša MM, Bojić T, Mazić SD, Kalauzi A. Generalized Poincaré plots analysis of heart period dynamics in different physiological conditions: Trained vs. untrained men. in PLOS One. 2019;14(7):e0219281.
doi:10.1371/journal.pone.0219281 .

Platiša, Mirjana M., Bojić, Tijana, Mazić, Sanja D., Kalauzi, Aleksandar, "Generalized Poincaré plots analysis of heart period dynamics in different physiological conditions: Trained vs. untrained men" in PLOS One, 14, no. 7 (2019):e0219281,
https://doi.org/10.1371/journal.pone.0219281 . .

TY  - JOUR
AU  - Kalauzi, Aleksandar
AU  - Vučković, Aleksandra
AU  - Bojić, Tijana
PY  - 2018
UR  - http://link.springer.com/10.1007/s11517-017-1746-3
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/7746
AB  - A number of measures, stemming from nonlinear dynamics, exist to estimate complexity of biomedical objects. In most cases they are appropriate, but sometimes unconventional measures, more suited for specific objects, are needed to perform the task. In our present work, we propose three new complexity measures to quantify complexity of topographic closed loops of alpha carrier frequency phase potentials (CFPP) of healthy humans in wake and drowsy states. EEG of ten adult individuals was recorded in both states, using a 14-channel montage. For each subject and each state, a topographic loop (circular directed graph) was constructed according to CFPP values. Circular complexity measure was obtained by summing angles which directed graph edges (arrows) form with the topographic center. Longitudinal complexity was defined as the sum of all arrow lengths, while intersecting complexity was introduced by counting the number of intersections of graph edges. Wilcoxon's signed-ranks test was used on the sets of these three measures, as well as on fractal dimension values of some loop properties, to test differences between loops obtained in wake vs. drowsy. While fractal dimension values were not significantly different, longitudinal and intersecting complexities, as well as anticlockwise circularity, were significantly increased in drowsy.
T2  - Medical & Biological Engineering & Computing
T1  - New complexity measures reveal that topographic loops of human alpha phase potentials are more complex in drowsy than in wake
VL  - 56
IS  - 6
SP  - 967
EP  - 978
DO  - 10.1007/s11517-017-1746-3
ER  - 

@article{
author = "Kalauzi, Aleksandar and Vučković, Aleksandra and Bojić, Tijana",
year = "2018",
abstract = "A number of measures, stemming from nonlinear dynamics, exist to estimate complexity of biomedical objects. In most cases they are appropriate, but sometimes unconventional measures, more suited for specific objects, are needed to perform the task. In our present work, we propose three new complexity measures to quantify complexity of topographic closed loops of alpha carrier frequency phase potentials (CFPP) of healthy humans in wake and drowsy states. EEG of ten adult individuals was recorded in both states, using a 14-channel montage. For each subject and each state, a topographic loop (circular directed graph) was constructed according to CFPP values. Circular complexity measure was obtained by summing angles which directed graph edges (arrows) form with the topographic center. Longitudinal complexity was defined as the sum of all arrow lengths, while intersecting complexity was introduced by counting the number of intersections of graph edges. Wilcoxon's signed-ranks test was used on the sets of these three measures, as well as on fractal dimension values of some loop properties, to test differences between loops obtained in wake vs. drowsy. While fractal dimension values were not significantly different, longitudinal and intersecting complexities, as well as anticlockwise circularity, were significantly increased in drowsy.",
journal = "Medical & Biological Engineering & Computing",
title = "New complexity measures reveal that topographic loops of human alpha phase potentials are more complex in drowsy than in wake",
volume = "56",
number = "6",
pages = "967-978",
doi = "10.1007/s11517-017-1746-3"
}

Kalauzi, A., Vučković, A.,& Bojić, T.. (2018). New complexity measures reveal that topographic loops of human alpha phase potentials are more complex in drowsy than in wake. in Medical & Biological Engineering & Computing, 56(6), 967-978.
https://doi.org/10.1007/s11517-017-1746-3

Kalauzi A, Vučković A, Bojić T. New complexity measures reveal that topographic loops of human alpha phase potentials are more complex in drowsy than in wake. in Medical & Biological Engineering & Computing. 2018;56(6):967-978.
doi:10.1007/s11517-017-1746-3 .

Kalauzi, Aleksandar, Vučković, Aleksandra, Bojić, Tijana, "New complexity measures reveal that topographic loops of human alpha phase potentials are more complex in drowsy than in wake" in Medical & Biological Engineering & Computing, 56, no. 6 (2018):967-978,
https://doi.org/10.1007/s11517-017-1746-3 . .

TY  - JOUR
AU  - Đikanović, Daniela
AU  - Devečerski, Aleksandar
AU  - Steinbach, Gabor
AU  - Simonović, Jasna
AU  - Matović, Branko
AU  - Garab, Gyozo 
AU  - Kalauzi, Aleksandar
AU  - Radotić, Ksenija
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1007
AB  - Interactions between macromolecules in the cell walls of different plant origin were compared, namely spruce wood (Picea omorika (PaniA double dagger) PurkiAe) as an example of softwood, maple wood (Acer platanoides L.) as a hardwood and maize stems (Zea mays L.) as a herbaceous plant from the grass family and widely used agricultural plant. Interactions of macromolecules in isolated cell walls from the three species were compared by using Fourier transform infrared spectroscopy, X-ray diffraction and fluorescence spectroscopy. Linear dichroism of the cell walls was observed by using differential polarization laser scanning microscope (DP-LSM), which provides information of macromolecular order. This method has not previously been used for comparison of the cell walls of various plant origins. It was shown that the maize cell walls have higher amount of hydrogen bonds that lead to more regular packing of cellulose molecules, simpler structure of lignin, and a higher crystallinity of the cell wall in relation to the walls of woody plants. DP-LSM and fluorescence spectroscopy results indicate that maize has simpler and more ordered structure than both woody species. The results of this work provide new data for comparison of the cell wall properties that may be important for selection of appropriate plant for possible applications as a source of biomass. This may be a contribution to the development of efficient deconstruction and separation technologies that enable release of sugar and aromatic compounds from the cell wall macromolecular structure.
PB  - Springer
T2  - Wood Science and Technology
T1  - Comparison of macromolecular interactions in the cell walls of hardwood, softwood and maize by fluorescence and FTIR spectroscopy, differential polarization laser scanning microscopy and X-ray diffraction
VL  - 50
IS  - 3
SP  - 547
EP  - 566
DO  - 10.1007/s00226-015-0792-y
ER  - 

@article{
author = "Đikanović, Daniela and Devečerski, Aleksandar and Steinbach, Gabor and Simonović, Jasna and Matović, Branko and Garab, Gyozo  and Kalauzi, Aleksandar and Radotić, Ksenija",
year = "2016",
abstract = "Interactions between macromolecules in the cell walls of different plant origin were compared, namely spruce wood (Picea omorika (PaniA double dagger) PurkiAe) as an example of softwood, maple wood (Acer platanoides L.) as a hardwood and maize stems (Zea mays L.) as a herbaceous plant from the grass family and widely used agricultural plant. Interactions of macromolecules in isolated cell walls from the three species were compared by using Fourier transform infrared spectroscopy, X-ray diffraction and fluorescence spectroscopy. Linear dichroism of the cell walls was observed by using differential polarization laser scanning microscope (DP-LSM), which provides information of macromolecular order. This method has not previously been used for comparison of the cell walls of various plant origins. It was shown that the maize cell walls have higher amount of hydrogen bonds that lead to more regular packing of cellulose molecules, simpler structure of lignin, and a higher crystallinity of the cell wall in relation to the walls of woody plants. DP-LSM and fluorescence spectroscopy results indicate that maize has simpler and more ordered structure than both woody species. The results of this work provide new data for comparison of the cell wall properties that may be important for selection of appropriate plant for possible applications as a source of biomass. This may be a contribution to the development of efficient deconstruction and separation technologies that enable release of sugar and aromatic compounds from the cell wall macromolecular structure.",
publisher = "Springer",
journal = "Wood Science and Technology",
title = "Comparison of macromolecular interactions in the cell walls of hardwood, softwood and maize by fluorescence and FTIR spectroscopy, differential polarization laser scanning microscopy and X-ray diffraction",
volume = "50",
number = "3",
pages = "547-566",
doi = "10.1007/s00226-015-0792-y"
}

Đikanović, D., Devečerski, A., Steinbach, G., Simonović, J., Matović, B., Garab, G., Kalauzi, A.,& Radotić, K.. (2016). Comparison of macromolecular interactions in the cell walls of hardwood, softwood and maize by fluorescence and FTIR spectroscopy, differential polarization laser scanning microscopy and X-ray diffraction. in Wood Science and Technology
Springer., 50(3), 547-566.
https://doi.org/10.1007/s00226-015-0792-y

Đikanović D, Devečerski A, Steinbach G, Simonović J, Matović B, Garab G, Kalauzi A, Radotić K. Comparison of macromolecular interactions in the cell walls of hardwood, softwood and maize by fluorescence and FTIR spectroscopy, differential polarization laser scanning microscopy and X-ray diffraction. in Wood Science and Technology. 2016;50(3):547-566.
doi:10.1007/s00226-015-0792-y .

Đikanović, Daniela, Devečerski, Aleksandar, Steinbach, Gabor, Simonović, Jasna, Matović, Branko, Garab, Gyozo , Kalauzi, Aleksandar, Radotić, Ksenija, "Comparison of macromolecular interactions in the cell walls of hardwood, softwood and maize by fluorescence and FTIR spectroscopy, differential polarization laser scanning microscopy and X-ray diffraction" in Wood Science and Technology, 50, no. 3 (2016):547-566,
https://doi.org/10.1007/s00226-015-0792-y . .

TY  - JOUR
AU  - Platiša, Mirjana M.
AU  - Bojić, Tijana
AU  - Pavlović, Siniša U.
AU  - Radovanovic, Nikola N.
AU  - Kalauzi, Aleksandar
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/941
AB  - Classical Poincare plot is a standard way to measure nonlinear regulation of cardiovascular control. In our work we propose a generalized form of Poincare plot where we track correlation between the duration of j preceding and k next RR intervals. The investigation was done in healthy subjects and patients with atrial fibrillation, by varying j,k LT = 100. In cases where j = k, in healthy subjects the typical pattern was observed by paths that were substituting scatterplots and that were initiated and ended by loops of Poincare plot points. This was not the case for atrial fibrillation patients where Poincare plot had a simple scattered form. More, a typical matrix of Pearsons correlation coefficients, r(j,k), showed different positions of local maxima, depending on the subjects health condition. In both groups, local maxima were grouped into four clusters which probably determined specific regulatory mechanisms according to correlations between the duration of symmetric and asymmetric observed RR intervals. We quantified matrices degrees of asymmetry and found that they were significantly different: distributed around zero in healthy, while being negative in atrial fibrillation. Also, Pearsons coefficients were higher in healthy than in atrial fibrillation or in signals with reshuffled intervals. Our hypothesis is that by this novel method we can observe heart rate regimes typical for baseline conditions and defense reaction in healthy subjects. These data indicate that neural control mechanisms of heart rate are operating in healthy subjects in contrast with atrial fibrillation, identifying it as the state of risk for stress-dependent pathologies. Regulatory regimes of heart rate can be further quantified and explored by the proposed novel method.
T2  - Frontiers in Neuroscience
T1  - Generalized Poincare Plots-A New Method for Evaluation of Regimes in Cardiac Neural Control in Atrial Fibrillation and Healthy Subjects
VL  - 10
SP  - 38
DO  - 10.3389/fnins.2016.00038
ER  - 

@article{
author = "Platiša, Mirjana M. and Bojić, Tijana and Pavlović, Siniša U. and Radovanovic, Nikola N. and Kalauzi, Aleksandar",
year = "2016",
abstract = "Classical Poincare plot is a standard way to measure nonlinear regulation of cardiovascular control. In our work we propose a generalized form of Poincare plot where we track correlation between the duration of j preceding and k next RR intervals. The investigation was done in healthy subjects and patients with atrial fibrillation, by varying j,k LT = 100. In cases where j = k, in healthy subjects the typical pattern was observed by paths that were substituting scatterplots and that were initiated and ended by loops of Poincare plot points. This was not the case for atrial fibrillation patients where Poincare plot had a simple scattered form. More, a typical matrix of Pearsons correlation coefficients, r(j,k), showed different positions of local maxima, depending on the subjects health condition. In both groups, local maxima were grouped into four clusters which probably determined specific regulatory mechanisms according to correlations between the duration of symmetric and asymmetric observed RR intervals. We quantified matrices degrees of asymmetry and found that they were significantly different: distributed around zero in healthy, while being negative in atrial fibrillation. Also, Pearsons coefficients were higher in healthy than in atrial fibrillation or in signals with reshuffled intervals. Our hypothesis is that by this novel method we can observe heart rate regimes typical for baseline conditions and defense reaction in healthy subjects. These data indicate that neural control mechanisms of heart rate are operating in healthy subjects in contrast with atrial fibrillation, identifying it as the state of risk for stress-dependent pathologies. Regulatory regimes of heart rate can be further quantified and explored by the proposed novel method.",
journal = "Frontiers in Neuroscience",
title = "Generalized Poincare Plots-A New Method for Evaluation of Regimes in Cardiac Neural Control in Atrial Fibrillation and Healthy Subjects",
volume = "10",
pages = "38",
doi = "10.3389/fnins.2016.00038"
}

Platiša, M. M., Bojić, T., Pavlović, S. U., Radovanovic, N. N.,& Kalauzi, A.. (2016). Generalized Poincare Plots-A New Method for Evaluation of Regimes in Cardiac Neural Control in Atrial Fibrillation and Healthy Subjects. in Frontiers in Neuroscience, 10, 38.
https://doi.org/10.3389/fnins.2016.00038

Platiša MM, Bojić T, Pavlović SU, Radovanovic NN, Kalauzi A. Generalized Poincare Plots-A New Method for Evaluation of Regimes in Cardiac Neural Control in Atrial Fibrillation and Healthy Subjects. in Frontiers in Neuroscience. 2016;10:38.
doi:10.3389/fnins.2016.00038 .

Platiša, Mirjana M., Bojić, Tijana, Pavlović, Siniša U., Radovanovic, Nikola N., Kalauzi, Aleksandar, "Generalized Poincare Plots-A New Method for Evaluation of Regimes in Cardiac Neural Control in Atrial Fibrillation and Healthy Subjects" in Frontiers in Neuroscience, 10 (2016):38,
https://doi.org/10.3389/fnins.2016.00038 . .

TY  - JOUR
AU  - Platiša, Mirjana M.
AU  - Bojić, Tijana
AU  - Pavlović, Siniša U.
AU  - Radovanovic, Nikola N.
AU  - Kalauzi, Aleksandar
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1332
AB  - Rearranged origin of heart rhythm in patients with atrial fibrillation (AF) influences the regulation of the heart and consequently the respiratory rhythm, and the bidirectional interaction of these rhythms not documented. Hence, we examined coupling of the RR interval and the respiration (Resp) signal by coherence, Granger causality and the cross-sample entropy method of time series analysis in patients with AF and a healthy control group. In healthy subjects, the influence of respiration on cardiac rhythm was found as increased coherence at the breathing frequency (BF) range, significantly stronger interaction and synchrony from Resp to RR than from RR to Resp. On the contrary, in patients with AF, coherence at BF diminished, there were no causal interactions between signals in both directions, which resulted in equally great asynchrony between them. In AF, the absence of full functionality of the sinoatrial node, as an integrator of neural cardiac control, resulted in diminished vagal modulation of heart periods and consequently impaired bidirectional cardio-respiratory interaction.
T2  - Biomedical Engineering / Biomedizinische Technik
T1  - Uncoupling of cardiac and respiratory rhythm in atrial fibrillation
VL  - 61
IS  - 6
SP  - 657
EP  - 663
DO  - 10.1515/bmt-2016-0057
ER  - 

@article{
author = "Platiša, Mirjana M. and Bojić, Tijana and Pavlović, Siniša U. and Radovanovic, Nikola N. and Kalauzi, Aleksandar",
year = "2016",
abstract = "Rearranged origin of heart rhythm in patients with atrial fibrillation (AF) influences the regulation of the heart and consequently the respiratory rhythm, and the bidirectional interaction of these rhythms not documented. Hence, we examined coupling of the RR interval and the respiration (Resp) signal by coherence, Granger causality and the cross-sample entropy method of time series analysis in patients with AF and a healthy control group. In healthy subjects, the influence of respiration on cardiac rhythm was found as increased coherence at the breathing frequency (BF) range, significantly stronger interaction and synchrony from Resp to RR than from RR to Resp. On the contrary, in patients with AF, coherence at BF diminished, there were no causal interactions between signals in both directions, which resulted in equally great asynchrony between them. In AF, the absence of full functionality of the sinoatrial node, as an integrator of neural cardiac control, resulted in diminished vagal modulation of heart periods and consequently impaired bidirectional cardio-respiratory interaction.",
journal = "Biomedical Engineering / Biomedizinische Technik",
title = "Uncoupling of cardiac and respiratory rhythm in atrial fibrillation",
volume = "61",
number = "6",
pages = "657-663",
doi = "10.1515/bmt-2016-0057"
}

Platiša, M. M., Bojić, T., Pavlović, S. U., Radovanovic, N. N.,& Kalauzi, A.. (2016). Uncoupling of cardiac and respiratory rhythm in atrial fibrillation. in Biomedical Engineering / Biomedizinische Technik, 61(6), 657-663.
https://doi.org/10.1515/bmt-2016-0057

Platiša MM, Bojić T, Pavlović SU, Radovanovic NN, Kalauzi A. Uncoupling of cardiac and respiratory rhythm in atrial fibrillation. in Biomedical Engineering / Biomedizinische Technik. 2016;61(6):657-663.
doi:10.1515/bmt-2016-0057 .

Platiša, Mirjana M., Bojić, Tijana, Pavlović, Siniša U., Radovanovic, Nikola N., Kalauzi, Aleksandar, "Uncoupling of cardiac and respiratory rhythm in atrial fibrillation" in Biomedical Engineering / Biomedizinische Technik, 61, no. 6 (2016):657-663,
https://doi.org/10.1515/bmt-2016-0057 . .

TY  - JOUR
AU  - Pešić, Milica
AU  - Podolski-Renić, Ana
AU  - Stojković, Sonja
AU  - Matović, Branko
AU  - Zmejkoski, Danica
AU  - Kojić, Vesna
AU  - Bogdanović, Gordana
AU  - Pavicevic, Aleksandra
AU  - Mojovic, Milos
AU  - Savić, Aleksandar
AU  - Milenković, Ivana
AU  - Kalauzi, Aleksandar
AU  - Radotić, Ksenija
PY  - 2015
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/519
AB  - Data on medical applications of cerium oxide nanoparticles CeO2 (CONP) are promising, yet information regarding their action in cells is incomplete and there are conflicting reports about in vitro toxicity. Herein, we have studied cytotoxic effect of CONP in several cancer and normal cell lines and their potential to change intracellular redox status. The IC50 was achieved only in two of eight tested cell lines, melanoma 518A2 and colorectal adenocarcinoma HT-29. Self-propagating room temperature method was applied to produce CONP with an average crystalline size of 4 nm. The results confirmed presence of Ce3+ and O2- vacancies. The induction of cell death by CONP and the production of reactive oxygen species (ROS) were analyzed by flow-cytometry. Free radicals related antioxidant capacity of the cells was studied by the reduction of stable free radical TEMPONE using electron spin resonance spectroscopy. CONP showed low or moderate cytotoxicity in cancer cell lines: adenocarcinoma DLD1 and multi-drug resistant DLD1-TxR, non-small cell lung carcinoma NCI-H460 and multi-drug resistant NCI-H460/R, while normal cell lines (keratinocytes HaCaT, lung fetal fibroblasts MRC-5) were insensitive. The most sensitive were 518A2 melanoma and HT-29 colorectal adenocarcinoma cell lines, with the IC50 values being between 100 and 200 mu M. Decreased rate of TEMPONE reduction and increased production of certain ROS species (peroxynitrite and hydrogen peroxide anion) indicates that free radical metabolism, thus redox status was changed, and antioxidant capacity damaged in the CONP treated 518A2 and HT-29 cells. In conclusion, changes in intracellular redox status induced by CONP are partly attributed to the prooxidant activity of the nanoparticles. Further, ROS induced cell damages might eventually lead to the cell death. However, low inhibitory potential of CONP in the other human cell lines tested indicates that CONP may be safe for human usage in industry and medicine. (C) 2015 Elsevier Ireland Ltd. All rights reserved.
T2  - Chemico-Biological Interactions
T1  - Anti-cancer effects of cerium oxide nanoparticles and its intracellular redox activity
VL  - 232
SP  - 85
EP  - 93
DO  - 10.1016/j.cbi.2015.03.013
ER  - 

@article{
author = "Pešić, Milica and Podolski-Renić, Ana and Stojković, Sonja and Matović, Branko and Zmejkoski, Danica and Kojić, Vesna and Bogdanović, Gordana and Pavicevic, Aleksandra and Mojovic, Milos and Savić, Aleksandar and Milenković, Ivana and Kalauzi, Aleksandar and Radotić, Ksenija",
year = "2015",
abstract = "Data on medical applications of cerium oxide nanoparticles CeO2 (CONP) are promising, yet information regarding their action in cells is incomplete and there are conflicting reports about in vitro toxicity. Herein, we have studied cytotoxic effect of CONP in several cancer and normal cell lines and their potential to change intracellular redox status. The IC50 was achieved only in two of eight tested cell lines, melanoma 518A2 and colorectal adenocarcinoma HT-29. Self-propagating room temperature method was applied to produce CONP with an average crystalline size of 4 nm. The results confirmed presence of Ce3+ and O2- vacancies. The induction of cell death by CONP and the production of reactive oxygen species (ROS) were analyzed by flow-cytometry. Free radicals related antioxidant capacity of the cells was studied by the reduction of stable free radical TEMPONE using electron spin resonance spectroscopy. CONP showed low or moderate cytotoxicity in cancer cell lines: adenocarcinoma DLD1 and multi-drug resistant DLD1-TxR, non-small cell lung carcinoma NCI-H460 and multi-drug resistant NCI-H460/R, while normal cell lines (keratinocytes HaCaT, lung fetal fibroblasts MRC-5) were insensitive. The most sensitive were 518A2 melanoma and HT-29 colorectal adenocarcinoma cell lines, with the IC50 values being between 100 and 200 mu M. Decreased rate of TEMPONE reduction and increased production of certain ROS species (peroxynitrite and hydrogen peroxide anion) indicates that free radical metabolism, thus redox status was changed, and antioxidant capacity damaged in the CONP treated 518A2 and HT-29 cells. In conclusion, changes in intracellular redox status induced by CONP are partly attributed to the prooxidant activity of the nanoparticles. Further, ROS induced cell damages might eventually lead to the cell death. However, low inhibitory potential of CONP in the other human cell lines tested indicates that CONP may be safe for human usage in industry and medicine. (C) 2015 Elsevier Ireland Ltd. All rights reserved.",
journal = "Chemico-Biological Interactions",
title = "Anti-cancer effects of cerium oxide nanoparticles and its intracellular redox activity",
volume = "232",
pages = "85-93",
doi = "10.1016/j.cbi.2015.03.013"
}

Pešić, M., Podolski-Renić, A., Stojković, S., Matović, B., Zmejkoski, D., Kojić, V., Bogdanović, G., Pavicevic, A., Mojovic, M., Savić, A., Milenković, I., Kalauzi, A.,& Radotić, K.. (2015). Anti-cancer effects of cerium oxide nanoparticles and its intracellular redox activity. in Chemico-Biological Interactions, 232, 85-93.
https://doi.org/10.1016/j.cbi.2015.03.013

Pešić M, Podolski-Renić A, Stojković S, Matović B, Zmejkoski D, Kojić V, Bogdanović G, Pavicevic A, Mojovic M, Savić A, Milenković I, Kalauzi A, Radotić K. Anti-cancer effects of cerium oxide nanoparticles and its intracellular redox activity. in Chemico-Biological Interactions. 2015;232:85-93.
doi:10.1016/j.cbi.2015.03.013 .

Pešić, Milica, Podolski-Renić, Ana, Stojković, Sonja, Matović, Branko, Zmejkoski, Danica, Kojić, Vesna, Bogdanović, Gordana, Pavicevic, Aleksandra, Mojovic, Milos, Savić, Aleksandar, Milenković, Ivana, Kalauzi, Aleksandar, Radotić, Ksenija, "Anti-cancer effects of cerium oxide nanoparticles and its intracellular redox activity" in Chemico-Biological Interactions, 232 (2015):85-93,
https://doi.org/10.1016/j.cbi.2015.03.013 . .

TY  - JOUR
AU  - Kalauzi, Aleksandar
AU  - Vučković, Aleksandra
AU  - Bojić, Tijana
PY  - 2015
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/475
AB  - Organization of resting state cortical networks is of fundamental importance for the phenomenon of awareness, which is altered in the first part of hypnagogic period (Hori stages 1-4). Our aim was to investigate the change in brain topography pattern of EEG alpha attractor correlation dimension (CD) in the period of transition from Hori stage 1 to 4. EEG of ten healthy adult individuals was recorded in the wake and drowsy states, using a 14 channel average reference montage, from which 91 bipolar channels were derived and filtered in the wider alpha (6-14 Hz) range. Sixty 1 s long epochs of each state and individual were subjected to CD calculation according to the Grassberger-Procaccia method. For such a collection of signals, two embedding dimensions, d = {5,10}, and 22 time delays 7 = 2-23 samples were explored. Optimal values were d = 10 and 7 = 18, where both saturation and second zero crossing of the autocorrelation function occurred. Bipolar channel CD underwent a significant decrease during the transition and showed a positive linear correlation with electrode distance, stronger in the wake individuals. Topographic distribution of bipolar channels with above median CD changed from longitudinal anterior-posterior pattern (awake) to a more diagonal pattern, with localization in posterior regions (drowsiness). Our data are in line with the literature reporting functional segregation of neuronal assemblies in anterior and posterior regions during this transition. Our results should contribute to understanding of complex reorganization of the cortical part of alpha generators during the wake/drowsy transition. (C) 2014 Elsevier B.V. All rights reserved.
T2  - International Journal of Psychophysiology
T1  - Topographic distribution of EEG alpha attractor correlation dimension values in wake and drowsy states in humans
VL  - 95
IS  - 3
SP  - 278
EP  - 291
DO  - 10.1016/j.ijpsycho.2014.11.008
ER  - 

@article{
author = "Kalauzi, Aleksandar and Vučković, Aleksandra and Bojić, Tijana",
year = "2015",
abstract = "Organization of resting state cortical networks is of fundamental importance for the phenomenon of awareness, which is altered in the first part of hypnagogic period (Hori stages 1-4). Our aim was to investigate the change in brain topography pattern of EEG alpha attractor correlation dimension (CD) in the period of transition from Hori stage 1 to 4. EEG of ten healthy adult individuals was recorded in the wake and drowsy states, using a 14 channel average reference montage, from which 91 bipolar channels were derived and filtered in the wider alpha (6-14 Hz) range. Sixty 1 s long epochs of each state and individual were subjected to CD calculation according to the Grassberger-Procaccia method. For such a collection of signals, two embedding dimensions, d = {5,10}, and 22 time delays 7 = 2-23 samples were explored. Optimal values were d = 10 and 7 = 18, where both saturation and second zero crossing of the autocorrelation function occurred. Bipolar channel CD underwent a significant decrease during the transition and showed a positive linear correlation with electrode distance, stronger in the wake individuals. Topographic distribution of bipolar channels with above median CD changed from longitudinal anterior-posterior pattern (awake) to a more diagonal pattern, with localization in posterior regions (drowsiness). Our data are in line with the literature reporting functional segregation of neuronal assemblies in anterior and posterior regions during this transition. Our results should contribute to understanding of complex reorganization of the cortical part of alpha generators during the wake/drowsy transition. (C) 2014 Elsevier B.V. All rights reserved.",
journal = "International Journal of Psychophysiology",
title = "Topographic distribution of EEG alpha attractor correlation dimension values in wake and drowsy states in humans",
volume = "95",
number = "3",
pages = "278-291",
doi = "10.1016/j.ijpsycho.2014.11.008"
}

Kalauzi, A., Vučković, A.,& Bojić, T.. (2015). Topographic distribution of EEG alpha attractor correlation dimension values in wake and drowsy states in humans. in International Journal of Psychophysiology, 95(3), 278-291.
https://doi.org/10.1016/j.ijpsycho.2014.11.008

Kalauzi A, Vučković A, Bojić T. Topographic distribution of EEG alpha attractor correlation dimension values in wake and drowsy states in humans. in International Journal of Psychophysiology. 2015;95(3):278-291.
doi:10.1016/j.ijpsycho.2014.11.008 .

Kalauzi, Aleksandar, Vučković, Aleksandra, Bojić, Tijana, "Topographic distribution of EEG alpha attractor correlation dimension values in wake and drowsy states in humans" in International Journal of Psychophysiology, 95, no. 3 (2015):278-291,
https://doi.org/10.1016/j.ijpsycho.2014.11.008 . .

TY  - JOUR
AU  - Kapidžić, Ana
AU  - Platiša, Mirjana M.
AU  - Bojić, Tijana
AU  - Kalauzi, Aleksandar
PY  - 2014
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/188
AB  - Our aim was to model the dependence of respiratory sinus arrhythmia (RSA) on the respiratory waveform and to elucidate underlying mechanisms of cardiorespiratory coupling. In 30 subjects, RR interval and respiratory signal were recorded during spontaneous and paced (0.1 Hz/0.15 Hz) breathing and their relationship was modeled by a first order linear differential equation. This model has two parameters: a0 (related to the instantaneous degree of abdominal expansion) and a1 (referring to the speed of abdominal expansion). Assuming that a0 represents slowly adapting pulmonary stretch receptors (SARs) and a1 SARs in coordination with other stretch receptors and central integrative coupling; then pulmonary stretch receptors relaying the instantaneous lung volume are the major factor determining cardiovagal output during inspiration. The models results depended on breathing frequency with the least error occurring during slow paced breathing. The role of vagal afferent neurons in cardiorespiratory coupling may relate to neurocardiovascular diseases in which weakened coupling among venous return, arterial pressure, heart rate and respiration produces cardiovagal instability. (C) 2014 Elsevier B.V. All rights reserved.
T2  - Respiratory Physiology and Neurobiology
T1  - RR interval-respiratory signal waveform modeling in human slow paced and spontaneous breathing
VL  - 203
SP  - 51
EP  - 59
DO  - 10.1016/j.resp.2014.08.004
ER  - 

@article{
author = "Kapidžić, Ana and Platiša, Mirjana M. and Bojić, Tijana and Kalauzi, Aleksandar",
year = "2014",
abstract = "Our aim was to model the dependence of respiratory sinus arrhythmia (RSA) on the respiratory waveform and to elucidate underlying mechanisms of cardiorespiratory coupling. In 30 subjects, RR interval and respiratory signal were recorded during spontaneous and paced (0.1 Hz/0.15 Hz) breathing and their relationship was modeled by a first order linear differential equation. This model has two parameters: a0 (related to the instantaneous degree of abdominal expansion) and a1 (referring to the speed of abdominal expansion). Assuming that a0 represents slowly adapting pulmonary stretch receptors (SARs) and a1 SARs in coordination with other stretch receptors and central integrative coupling; then pulmonary stretch receptors relaying the instantaneous lung volume are the major factor determining cardiovagal output during inspiration. The models results depended on breathing frequency with the least error occurring during slow paced breathing. The role of vagal afferent neurons in cardiorespiratory coupling may relate to neurocardiovascular diseases in which weakened coupling among venous return, arterial pressure, heart rate and respiration produces cardiovagal instability. (C) 2014 Elsevier B.V. All rights reserved.",
journal = "Respiratory Physiology and Neurobiology",
title = "RR interval-respiratory signal waveform modeling in human slow paced and spontaneous breathing",
volume = "203",
pages = "51-59",
doi = "10.1016/j.resp.2014.08.004"
}

Kapidžić, A., Platiša, M. M., Bojić, T.,& Kalauzi, A.. (2014). RR interval-respiratory signal waveform modeling in human slow paced and spontaneous breathing. in Respiratory Physiology and Neurobiology, 203, 51-59.
https://doi.org/10.1016/j.resp.2014.08.004

Kapidžić A, Platiša MM, Bojić T, Kalauzi A. RR interval-respiratory signal waveform modeling in human slow paced and spontaneous breathing. in Respiratory Physiology and Neurobiology. 2014;203:51-59.
doi:10.1016/j.resp.2014.08.004 .

Kapidžić, Ana, Platiša, Mirjana M., Bojić, Tijana, Kalauzi, Aleksandar, "RR interval-respiratory signal waveform modeling in human slow paced and spontaneous breathing" in Respiratory Physiology and Neurobiology, 203 (2014):51-59,
https://doi.org/10.1016/j.resp.2014.08.004 . .

TY  - JOUR
AU  - Kapidžić, Ana
AU  - Platiša, Mirjana M.
AU  - Bojić, Tijana
AU  - Kalauzi, Aleksandar
PY  - 2014
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/338
AB  - We examined the effects of gender and age in young and middle-aged subjects on the level of cardiorespiratory interaction by analyzing properties of cardiac, respiratory and cardiac-respiratory regulatory mechanisms under paced breathing. In 56 healthy subjects, ECG (RR interval) and respiratory signal were simultaneously acquired in supine position at paced (0.1-0.45 Hz, steps of 0.05 Hz) and spontaneous breathing. The participants were divided into gender matched group of young adults (19-25 years old) and middle-aged adults (35-44 years old). Power spectral analysis was applied on RR interval time series and spectral components in very low frequency (VLF), low frequency (LF) and high frequency (HF) ranges were computed. We also calculated Sample entropy of RR interval series (SampEnRR), respiratory series (SampEnResp), and their cross-sample entropy (cross-SampEn). Under paced breathing, reduction of all spectral powers with age (p LT 0.05) is not gender dependent but reduction of some entropy measures is; SampEnRR and SampEnResp were lower only in men (p LT 0.05). In the middle-aged subjects, effect of gender on spectral measures is significant; males had lower HF (p LT 0.05). Pattern of dependencies of SampEn and cross-SampEn on paced breathing frequency were significantly different in men (young vs. middle-aged, p = 0.001 and p = 0.037) and in middle-aged subjects (females vs. males, p = 0.011 and p = 0.008). In middle-aged males, lower entropy measures indicated reduced and less complex partial cardiac and respiratory control, and central cardio-respiratory control. In conclusion, in healthy middle-aged subjects changes in cardio-respiratory coupling are detectable only in males. (C) 2014 IPEM. Published by Elsevier Ltd. All rights reserved.
T2  - Medical Engineering and Physics
T1  - Nonlinear properties of cardiac rhythm and respiratory signal under paced breathing in young and middle-aged healthy subjects
VL  - 36
IS  - 12
SP  - 1577
EP  - 1584
DO  - 10.1016/j.medengphy.2014.08.007
ER  - 

@article{
author = "Kapidžić, Ana and Platiša, Mirjana M. and Bojić, Tijana and Kalauzi, Aleksandar",
year = "2014",
abstract = "We examined the effects of gender and age in young and middle-aged subjects on the level of cardiorespiratory interaction by analyzing properties of cardiac, respiratory and cardiac-respiratory regulatory mechanisms under paced breathing. In 56 healthy subjects, ECG (RR interval) and respiratory signal were simultaneously acquired in supine position at paced (0.1-0.45 Hz, steps of 0.05 Hz) and spontaneous breathing. The participants were divided into gender matched group of young adults (19-25 years old) and middle-aged adults (35-44 years old). Power spectral analysis was applied on RR interval time series and spectral components in very low frequency (VLF), low frequency (LF) and high frequency (HF) ranges were computed. We also calculated Sample entropy of RR interval series (SampEnRR), respiratory series (SampEnResp), and their cross-sample entropy (cross-SampEn). Under paced breathing, reduction of all spectral powers with age (p LT 0.05) is not gender dependent but reduction of some entropy measures is; SampEnRR and SampEnResp were lower only in men (p LT 0.05). In the middle-aged subjects, effect of gender on spectral measures is significant; males had lower HF (p LT 0.05). Pattern of dependencies of SampEn and cross-SampEn on paced breathing frequency were significantly different in men (young vs. middle-aged, p = 0.001 and p = 0.037) and in middle-aged subjects (females vs. males, p = 0.011 and p = 0.008). In middle-aged males, lower entropy measures indicated reduced and less complex partial cardiac and respiratory control, and central cardio-respiratory control. In conclusion, in healthy middle-aged subjects changes in cardio-respiratory coupling are detectable only in males. (C) 2014 IPEM. Published by Elsevier Ltd. All rights reserved.",
journal = "Medical Engineering and Physics",
title = "Nonlinear properties of cardiac rhythm and respiratory signal under paced breathing in young and middle-aged healthy subjects",
volume = "36",
number = "12",
pages = "1577-1584",
doi = "10.1016/j.medengphy.2014.08.007"
}

Kapidžić, A., Platiša, M. M., Bojić, T.,& Kalauzi, A.. (2014). Nonlinear properties of cardiac rhythm and respiratory signal under paced breathing in young and middle-aged healthy subjects. in Medical Engineering and Physics, 36(12), 1577-1584.
https://doi.org/10.1016/j.medengphy.2014.08.007

Kapidžić A, Platiša MM, Bojić T, Kalauzi A. Nonlinear properties of cardiac rhythm and respiratory signal under paced breathing in young and middle-aged healthy subjects. in Medical Engineering and Physics. 2014;36(12):1577-1584.
doi:10.1016/j.medengphy.2014.08.007 .

Kapidžić, Ana, Platiša, Mirjana M., Bojić, Tijana, Kalauzi, Aleksandar, "Nonlinear properties of cardiac rhythm and respiratory signal under paced breathing in young and middle-aged healthy subjects" in Medical Engineering and Physics, 36, no. 12 (2014):1577-1584,
https://doi.org/10.1016/j.medengphy.2014.08.007 . .

TY  - JOUR
AU  - Kalauzi, Aleksandar
AU  - Bojić, Tijana
AU  - Vučković, Aleksandra
PY  - 2012
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/4908
AB  - The exact mathematical relationship between FFT spectrum and fractal dimension (FD) of an experimentally recorded signal is not known. In this work, we tried to calculate signal FD directly from its Fourier amplitudes. First, dependence of Higuchis FD of mathematical sinusoids on their individual frequencies was modeled with a two-parameter exponential function. Next, FD of a finite sum of sinusoids was found to be a weighted average of their FDs, weighting factors being their Fourier amplitudes raised to a fractal degree. Exponent dependence on frequency was modeled with exponential, power and logarithmic functions. A set of 280 EEG signals and Weierstrass functions were analyzed. Cross-validation was done within EEG signals and between them and Weierstrass functions. Exponential dependence of fractal exponents on frequency was found to be the most accurate. In this work, signal FD was for the first time expressed as a fractal weighted average of FD values of its Fourier components, also allowing researchers to perform direct estimation of signal fractal dimension from its FFT spectrum.
T2  - Medical and Biological Engineering and Computing
T1  - Modeling the relationship between Higuchis fractal dimension and Fourier spectra of physiological signals
VL  - 50
IS  - 7
SP  - 689
EP  - 699
DO  - 10.1007/s11517-012-0913-9
ER  - 

@article{
author = "Kalauzi, Aleksandar and Bojić, Tijana and Vučković, Aleksandra",
year = "2012",
abstract = "The exact mathematical relationship between FFT spectrum and fractal dimension (FD) of an experimentally recorded signal is not known. In this work, we tried to calculate signal FD directly from its Fourier amplitudes. First, dependence of Higuchis FD of mathematical sinusoids on their individual frequencies was modeled with a two-parameter exponential function. Next, FD of a finite sum of sinusoids was found to be a weighted average of their FDs, weighting factors being their Fourier amplitudes raised to a fractal degree. Exponent dependence on frequency was modeled with exponential, power and logarithmic functions. A set of 280 EEG signals and Weierstrass functions were analyzed. Cross-validation was done within EEG signals and between them and Weierstrass functions. Exponential dependence of fractal exponents on frequency was found to be the most accurate. In this work, signal FD was for the first time expressed as a fractal weighted average of FD values of its Fourier components, also allowing researchers to perform direct estimation of signal fractal dimension from its FFT spectrum.",
journal = "Medical and Biological Engineering and Computing",
title = "Modeling the relationship between Higuchis fractal dimension and Fourier spectra of physiological signals",
volume = "50",
number = "7",
pages = "689-699",
doi = "10.1007/s11517-012-0913-9"
}

Kalauzi, A., Bojić, T.,& Vučković, A.. (2012). Modeling the relationship between Higuchis fractal dimension and Fourier spectra of physiological signals. in Medical and Biological Engineering and Computing, 50(7), 689-699.
https://doi.org/10.1007/s11517-012-0913-9

Kalauzi A, Bojić T, Vučković A. Modeling the relationship between Higuchis fractal dimension and Fourier spectra of physiological signals. in Medical and Biological Engineering and Computing. 2012;50(7):689-699.
doi:10.1007/s11517-012-0913-9 .

Kalauzi, Aleksandar, Bojić, Tijana, Vučković, Aleksandra, "Modeling the relationship between Higuchis fractal dimension and Fourier spectra of physiological signals" in Medical and Biological Engineering and Computing, 50, no. 7 (2012):689-699,
https://doi.org/10.1007/s11517-012-0913-9 . .

TY  - JOUR
AU  - Kalauzi, Aleksandar
AU  - Vučković, Aleksandra
AU  - Bojić, Tijana
PY  - 2012
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/5215
AB  - Phases of alpha oscillations recorded by EEG were typically studied in the context of event or task related experiments, rarely during spontaneous alpha activity and in different brain states. During wake-to-drowsy transition they change unevenly, depending on the brain region. To explore their dynamics, we recorded ten adult healthy individuals in these two states. Alpha waves were treated as stable frequency and variable amplitude signals with one carrier frequency (CF). A method for calculating their CF phase shifts (CFPS) and CF phase potentials (CFPP) was developed and verified on surrogate signals as more accurate than phase shifts of Fourier components. Probability density estimate (PDE) of CFPS, CFPP and CF phase locking showed that frontal and fronto-temporal areas of the cortex underwent more extensive changes than posterior regions. The greatest differences were found between pairs of channels involving F7, F8, F3 and F4 (PDE of CFPS); F7, F8. T3 and 14 (CFPP); F7, F8, F3, F4, C3, C4 and T3 (decrease in CF phase locking). A topographic distribution of channels with above the average phase locking in the wake state revealed two separate regions occupying anterior and posterior brain areas (with intra regional and inter hemispheric connections). These regions merged and became mutually phase locked longitudinally in the drowsy state. Changes occurring primarily in the frontal and fronto-temporal regions correlated with an early decrease of alertness. Areas of increased phase locking might be correlated with topography of synchronous neuronal assemblies conceptualized within neural correlates of consciousness. (C) 2012 Elsevier B.V. All rights reserved.
T2  - International Journal of Psychophysiology
T1  - EEG alpha phase shifts during transition from wakefulness to drowsiness
VL  - 86
IS  - 3
SP  - 195
EP  - 205
DO  - 10.1016/j.ijpsycho.2012.04.012
ER  - 

@article{
author = "Kalauzi, Aleksandar and Vučković, Aleksandra and Bojić, Tijana",
year = "2012",
abstract = "Phases of alpha oscillations recorded by EEG were typically studied in the context of event or task related experiments, rarely during spontaneous alpha activity and in different brain states. During wake-to-drowsy transition they change unevenly, depending on the brain region. To explore their dynamics, we recorded ten adult healthy individuals in these two states. Alpha waves were treated as stable frequency and variable amplitude signals with one carrier frequency (CF). A method for calculating their CF phase shifts (CFPS) and CF phase potentials (CFPP) was developed and verified on surrogate signals as more accurate than phase shifts of Fourier components. Probability density estimate (PDE) of CFPS, CFPP and CF phase locking showed that frontal and fronto-temporal areas of the cortex underwent more extensive changes than posterior regions. The greatest differences were found between pairs of channels involving F7, F8, F3 and F4 (PDE of CFPS); F7, F8. T3 and 14 (CFPP); F7, F8, F3, F4, C3, C4 and T3 (decrease in CF phase locking). A topographic distribution of channels with above the average phase locking in the wake state revealed two separate regions occupying anterior and posterior brain areas (with intra regional and inter hemispheric connections). These regions merged and became mutually phase locked longitudinally in the drowsy state. Changes occurring primarily in the frontal and fronto-temporal regions correlated with an early decrease of alertness. Areas of increased phase locking might be correlated with topography of synchronous neuronal assemblies conceptualized within neural correlates of consciousness. (C) 2012 Elsevier B.V. All rights reserved.",
journal = "International Journal of Psychophysiology",
title = "EEG alpha phase shifts during transition from wakefulness to drowsiness",
volume = "86",
number = "3",
pages = "195-205",
doi = "10.1016/j.ijpsycho.2012.04.012"
}

Kalauzi, A., Vučković, A.,& Bojić, T.. (2012). EEG alpha phase shifts during transition from wakefulness to drowsiness. in International Journal of Psychophysiology, 86(3), 195-205.
https://doi.org/10.1016/j.ijpsycho.2012.04.012

Kalauzi A, Vučković A, Bojić T. EEG alpha phase shifts during transition from wakefulness to drowsiness. in International Journal of Psychophysiology. 2012;86(3):195-205.
doi:10.1016/j.ijpsycho.2012.04.012 .

Kalauzi, Aleksandar, Vučković, Aleksandra, Bojić, Tijana, "EEG alpha phase shifts during transition from wakefulness to drowsiness" in International Journal of Psychophysiology, 86, no. 3 (2012):195-205,
https://doi.org/10.1016/j.ijpsycho.2012.04.012 . .

TY  - JOUR
AU  - Bojić, Tijana
AU  - Vučković, Aleksandra
AU  - Kalauzi, Aleksandar
PY  - 2010
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8869
AB  - Aim of this preliminary study was to examine and compare topographic distribution of Higuchi's fractal dimension (FD, measure of signal complexity) of EEG signals between states of relaxed wakefulness and drowsiness, as well as their FD differences. The experiments were performed on 10 healthy individuals using a fourteen-channel montage. An explanation is offered on the causes of the detected FD changes. FD values of 60 s records belonging to wake (Hori's stage 1) and drowsy (Hori's stages 2-4) states were calculated for each channel and each subject. In 136 out of 140 epochs an increase in FD was obtained. Relationship between signal FD and its relative alpha amplitude was mathematically modeled and we quantitatively demonstrated that the increase in FD was predominantly due to a reduction in alpha activity. The model was generalized to include other EEG oscillations. By averaging FD values for each channel across 10 subjects, four clusters (O2O1; T6P4T5P3; C3F3F4C4F8F7; T4T3) for the wake and two clusters (O2O1P3T6P4T5; C3C4F4F3F8T4T3F7) for the drowsy state were statistically verified. Topographic distribution of FD values in wakefulness showed a lateral symmetry and a partial fronto-occipital gradient. In drowsiness, a reduction in the number of clusters was detected, due to regrouping of channels T3, T4, O1 and O2. Topographic distribution of absolute FD differences revealed largest values at F7, O1 and F3. Reorganization of channel clusters showed that regionalized brain activity, specific for wakefulness, became more global by entering into drowsiness. Since the global increase in FD during wake-to-drowsy transition correlated with the decrease of alpha power, we inferred that increase of EEG complexity may not necessarily be an index of brain activation. © 2009 Elsevier Ltd. All rights reserved.
T2  - Journal of Theoretical Biology
T1  - Modeling EEG fractal dimension changes in wake and drowsy states in humans—a preliminary study
VL  - 262
IS  - 2
SP  - 214
EP  - 222
DO  - 10.1016/j.jtbi.2009.10.001
ER  - 

@article{
author = "Bojić, Tijana and Vučković, Aleksandra and Kalauzi, Aleksandar",
year = "2010",
abstract = "Aim of this preliminary study was to examine and compare topographic distribution of Higuchi's fractal dimension (FD, measure of signal complexity) of EEG signals between states of relaxed wakefulness and drowsiness, as well as their FD differences. The experiments were performed on 10 healthy individuals using a fourteen-channel montage. An explanation is offered on the causes of the detected FD changes. FD values of 60 s records belonging to wake (Hori's stage 1) and drowsy (Hori's stages 2-4) states were calculated for each channel and each subject. In 136 out of 140 epochs an increase in FD was obtained. Relationship between signal FD and its relative alpha amplitude was mathematically modeled and we quantitatively demonstrated that the increase in FD was predominantly due to a reduction in alpha activity. The model was generalized to include other EEG oscillations. By averaging FD values for each channel across 10 subjects, four clusters (O2O1; T6P4T5P3; C3F3F4C4F8F7; T4T3) for the wake and two clusters (O2O1P3T6P4T5; C3C4F4F3F8T4T3F7) for the drowsy state were statistically verified. Topographic distribution of FD values in wakefulness showed a lateral symmetry and a partial fronto-occipital gradient. In drowsiness, a reduction in the number of clusters was detected, due to regrouping of channels T3, T4, O1 and O2. Topographic distribution of absolute FD differences revealed largest values at F7, O1 and F3. Reorganization of channel clusters showed that regionalized brain activity, specific for wakefulness, became more global by entering into drowsiness. Since the global increase in FD during wake-to-drowsy transition correlated with the decrease of alpha power, we inferred that increase of EEG complexity may not necessarily be an index of brain activation. © 2009 Elsevier Ltd. All rights reserved.",
journal = "Journal of Theoretical Biology",
title = "Modeling EEG fractal dimension changes in wake and drowsy states in humans—a preliminary study",
volume = "262",
number = "2",
pages = "214-222",
doi = "10.1016/j.jtbi.2009.10.001"
}

Bojić, T., Vučković, A.,& Kalauzi, A.. (2010). Modeling EEG fractal dimension changes in wake and drowsy states in humans—a preliminary study. in Journal of Theoretical Biology, 262(2), 214-222.
https://doi.org/10.1016/j.jtbi.2009.10.001

Bojić T, Vučković A, Kalauzi A. Modeling EEG fractal dimension changes in wake and drowsy states in humans—a preliminary study. in Journal of Theoretical Biology. 2010;262(2):214-222.
doi:10.1016/j.jtbi.2009.10.001 .

Bojić, Tijana, Vučković, Aleksandra, Kalauzi, Aleksandar, "Modeling EEG fractal dimension changes in wake and drowsy states in humans—a preliminary study" in Journal of Theoretical Biology, 262, no. 2 (2010):214-222,
https://doi.org/10.1016/j.jtbi.2009.10.001 . .

TY  - JOUR
AU  - Kalauzi, Aleksandar
AU  - Bojić, Tijana
AU  - Rakić, Ljubisav
PY  - 2009
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8870
AB  - Background: Nonlinear methods provide a direct way of estimating complexity of one-dimensional sampled signals through calculation of Higuchi's fractal dimension (1<FD<2). In most cases the signal is treated as being characterized by one value of FD and consequently analyzed as one epoch or, if divided into more epochs, often only mean and standard deviation of epoch FD are calculated. If its complexity variation (or running fractal dimension), FD(t), is to be extracted, a moving window (epoch) approach is needed. However, due to low-pass filtering properties of moving windows, short epochs are preferred. Since Higuchi's method is based on consecutive reduction of signal sampling frequency, it is not suitable for estimating FD of very short epochs (N < 100 samples).Results: In this work we propose a new and simple way to estimate FD for N < 100 by introducing 'normalized length density' of a signal epoch,.where yn(i) represents the ith signal sample after amplitude normalization. The actual calculation of signal FD is based on construction of a monotonic calibration curve, FD = f(NLD), on a set of Weierstrass functions, for which FD values are given theoretically. The two existing methods, Higuchi's and consecutive differences, applied simultaneously on signals with constant FD (white noise and Brownian motion), showed that standard deviation of calculated window FD (FDw) increased sharply as the epoch became shorter. However, in case of the new NLD method a considerably lower scattering was obtained, especially for N < 30, at the expense of some lower accuracy in calculating average FDw. Consequently, more accurate reconstruction of FD waveforms was obtained when synthetic signals were analyzed, containig short alternating epochs of two or three different FD values. Additionally, scatter plots of FDwof an occipital human EEG signal for 10 sample epochs demontrated that Higuchi's estimations for some epochs exceeded the theoretical FD limits, while NLD-derived values did not.Conclusion: The presented approach was more accurate than the existing two methods in FD(t) extraction for very short epochs and could be used in physiological signals when FD is expected to change abruptly, such as short phasic phenomena or transient artefacts, as well as in other fields of science. © 2009 Kalauzi et al; licensee BioMed Central Ltd.
T2  - Nonlinear Biomedical Physics
T1  - Extracting complexity waveforms from one-dimensional signals
VL  - 3
IS  - 1
SP  - 8
DO  - 10.1186/1753-4631-3-8
ER  - 

@article{
author = "Kalauzi, Aleksandar and Bojić, Tijana and Rakić, Ljubisav",
year = "2009",
abstract = "Background: Nonlinear methods provide a direct way of estimating complexity of one-dimensional sampled signals through calculation of Higuchi's fractal dimension (1<FD<2). In most cases the signal is treated as being characterized by one value of FD and consequently analyzed as one epoch or, if divided into more epochs, often only mean and standard deviation of epoch FD are calculated. If its complexity variation (or running fractal dimension), FD(t), is to be extracted, a moving window (epoch) approach is needed. However, due to low-pass filtering properties of moving windows, short epochs are preferred. Since Higuchi's method is based on consecutive reduction of signal sampling frequency, it is not suitable for estimating FD of very short epochs (N < 100 samples).Results: In this work we propose a new and simple way to estimate FD for N < 100 by introducing 'normalized length density' of a signal epoch,.where yn(i) represents the ith signal sample after amplitude normalization. The actual calculation of signal FD is based on construction of a monotonic calibration curve, FD = f(NLD), on a set of Weierstrass functions, for which FD values are given theoretically. The two existing methods, Higuchi's and consecutive differences, applied simultaneously on signals with constant FD (white noise and Brownian motion), showed that standard deviation of calculated window FD (FDw) increased sharply as the epoch became shorter. However, in case of the new NLD method a considerably lower scattering was obtained, especially for N < 30, at the expense of some lower accuracy in calculating average FDw. Consequently, more accurate reconstruction of FD waveforms was obtained when synthetic signals were analyzed, containig short alternating epochs of two or three different FD values. Additionally, scatter plots of FDwof an occipital human EEG signal for 10 sample epochs demontrated that Higuchi's estimations for some epochs exceeded the theoretical FD limits, while NLD-derived values did not.Conclusion: The presented approach was more accurate than the existing two methods in FD(t) extraction for very short epochs and could be used in physiological signals when FD is expected to change abruptly, such as short phasic phenomena or transient artefacts, as well as in other fields of science. © 2009 Kalauzi et al; licensee BioMed Central Ltd.",
journal = "Nonlinear Biomedical Physics",
title = "Extracting complexity waveforms from one-dimensional signals",
volume = "3",
number = "1",
pages = "8",
doi = "10.1186/1753-4631-3-8"
}

Kalauzi, A., Bojić, T.,& Rakić, L.. (2009). Extracting complexity waveforms from one-dimensional signals. in Nonlinear Biomedical Physics, 3(1), 8.
https://doi.org/10.1186/1753-4631-3-8

Kalauzi A, Bojić T, Rakić L. Extracting complexity waveforms from one-dimensional signals. in Nonlinear Biomedical Physics. 2009;3(1):8.
doi:10.1186/1753-4631-3-8 .

Kalauzi, Aleksandar, Bojić, Tijana, Rakić, Ljubisav, "Extracting complexity waveforms from one-dimensional signals" in Nonlinear Biomedical Physics, 3, no. 1 (2009):8,
https://doi.org/10.1186/1753-4631-3-8 . .

TY  - JOUR
AU  - Bojić, Tijana
AU  - Šaponjić, Jasna
AU  - Radulovački, Miodrag
AU  - Carley, David W
AU  - Kalauzi, Aleksandar
PY  - 2008
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8871
AB  - We applied a novel approach to respiratory waveform analysis-Monotone Signal Segments Analysis (MSSA) on 6-h recordings of respiratory signals in rats. To validate MSSA as a respiratory signal analysis tool we tested it by detecting: breaths and breath-to-breath intervals; respiratory timing and volume modes; and changes in respiratory pattern caused by lesions of monoaminergic systems in rats. MSSA differentiated three respiratory timing (tachypneic, eupneic, bradypneic-apneic), and three volume (artifacts, normovolemic, hypervolemic-sighs) modes. Lesion-induced respiratory pattern modulation was visible as shifts in the distributions of monotone signal segment amplitudes, and of breath-to-breath intervals. Specifically, noradrenergic lesion induced an increase in mean volume (p ≤ 0.03), with no change of the mean breath-to-breath interval duration (p ≥ 0.06). MSSA of timing modes detected noradrenergic lesion-induced interdependent changes in the balance of eupneic (decrease; p ≤ 0.02), and tachypneic (an increase; p ≤ 0.02) breath intervals with respect to control. In terms of breath durations within each timing mode, there was a tendency toward prolongation of the eupneic (p ≤ 0.08) and bradypneic-apneic (p ≤ 0.06) intervals. These results demonstrate that MSSA is sensitive to subtle shifts in respiratory rhythmogenesis not detectable by simple respiratory pattern descriptive statistics. MSSA represents a potentially valuable new tool for investigations of respiratory pattern control. © 2008 Elsevier B.V. All rights reserved.
T2  - Respiratory Physiology and Neurobiology
T1  - Monotone Signal Segments Analysis as a novel method of breath detection and breath-to-breath interval analysis in rat
VL  - 161
IS  - 3
SP  - 273
EP  - 280
DO  - 10.1016/j.resp.2008.03.001
ER  - 

@article{
author = "Bojić, Tijana and Šaponjić, Jasna and Radulovački, Miodrag and Carley, David W and Kalauzi, Aleksandar",
year = "2008",
abstract = "We applied a novel approach to respiratory waveform analysis-Monotone Signal Segments Analysis (MSSA) on 6-h recordings of respiratory signals in rats. To validate MSSA as a respiratory signal analysis tool we tested it by detecting: breaths and breath-to-breath intervals; respiratory timing and volume modes; and changes in respiratory pattern caused by lesions of monoaminergic systems in rats. MSSA differentiated three respiratory timing (tachypneic, eupneic, bradypneic-apneic), and three volume (artifacts, normovolemic, hypervolemic-sighs) modes. Lesion-induced respiratory pattern modulation was visible as shifts in the distributions of monotone signal segment amplitudes, and of breath-to-breath intervals. Specifically, noradrenergic lesion induced an increase in mean volume (p ≤ 0.03), with no change of the mean breath-to-breath interval duration (p ≥ 0.06). MSSA of timing modes detected noradrenergic lesion-induced interdependent changes in the balance of eupneic (decrease; p ≤ 0.02), and tachypneic (an increase; p ≤ 0.02) breath intervals with respect to control. In terms of breath durations within each timing mode, there was a tendency toward prolongation of the eupneic (p ≤ 0.08) and bradypneic-apneic (p ≤ 0.06) intervals. These results demonstrate that MSSA is sensitive to subtle shifts in respiratory rhythmogenesis not detectable by simple respiratory pattern descriptive statistics. MSSA represents a potentially valuable new tool for investigations of respiratory pattern control. © 2008 Elsevier B.V. All rights reserved.",
journal = "Respiratory Physiology and Neurobiology",
title = "Monotone Signal Segments Analysis as a novel method of breath detection and breath-to-breath interval analysis in rat",
volume = "161",
number = "3",
pages = "273-280",
doi = "10.1016/j.resp.2008.03.001"
}

Bojić, T., Šaponjić, J., Radulovački, M., Carley, D. W.,& Kalauzi, A.. (2008). Monotone Signal Segments Analysis as a novel method of breath detection and breath-to-breath interval analysis in rat. in Respiratory Physiology and Neurobiology, 161(3), 273-280.
https://doi.org/10.1016/j.resp.2008.03.001

Bojić T, Šaponjić J, Radulovački M, Carley DW, Kalauzi A. Monotone Signal Segments Analysis as a novel method of breath detection and breath-to-breath interval analysis in rat. in Respiratory Physiology and Neurobiology. 2008;161(3):273-280.
doi:10.1016/j.resp.2008.03.001 .

Bojić, Tijana, Šaponjić, Jasna, Radulovački, Miodrag, Carley, David W, Kalauzi, Aleksandar, "Monotone Signal Segments Analysis as a novel method of breath detection and breath-to-breath interval analysis in rat" in Respiratory Physiology and Neurobiology, 161, no. 3 (2008):273-280,
https://doi.org/10.1016/j.resp.2008.03.001 . .

TY  - JOUR
AU  - Bojić, Tijana
AU  - Šaponjić, Jasna
AU  - Radulovački, Miodrag
AU  - Carley, David W
AU  - Kalauzi, Aleksandar
PY  - 2008
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8878
AB  - We applied a novel approach to respiratory waveform analysis-Monotone Signal Segments Analysis (MSSA) on 6-h recordings of respiratory signals in rats. To validate MSSA as a respiratory signal analysis tool we tested it by detecting: breaths and breath-to-breath intervals; respiratory timing and volume modes; and changes in respiratory pattern caused by lesions of monoaminergic systems in rats. MSSA differentiated three respiratory timing (tachypneic, eupneic, bradypneic-apneic), and three volume (artifacts, normovolemic, hypervolemic-sighs) modes. Lesion-induced respiratory pattern modulation was visible as shifts in the distributions of monotone signal segment amplitudes, and of breath-to-breath intervals. Specifically, noradrenergic lesion induced an increase in mean volume (p ≤ 0.03), with no change of the mean breath-to-breath interval duration (p ≥ 0.06). MSSA of timing modes detected noradrenergic lesion-induced interdependent changes in the balance of eupneic (decrease; p ≤ 0.02), and tachypneic (an increase; p ≤ 0.02) breath intervals with respect to control. In terms of breath durations within each timing mode, there was a tendency toward prolongation of the eupneic (p ≤ 0.08) and bradypneic-apneic (p ≤ 0.06) intervals. These results demonstrate that MSSA is sensitive to subtle shifts in respiratory rhythmogenesis not detectable by simple respiratory pattern descriptive statistics. MSSA represents a potentially valuable new tool for investigations of respiratory pattern control. © 2008 Elsevier B.V. All rights reserved.
T2  - Respiratory Physiology and Neurobiology
T1  - Monotone Signal Segments Analysis as a novel method of breath detection and breath-to-breath interval analysis in rat
VL  - 161
IS  - 3
SP  - 273
EP  - 280
DO  - 10.1016/j.resp.2008.03.001
ER  - 

@article{
author = "Bojić, Tijana and Šaponjić, Jasna and Radulovački, Miodrag and Carley, David W and Kalauzi, Aleksandar",
year = "2008",
abstract = "We applied a novel approach to respiratory waveform analysis-Monotone Signal Segments Analysis (MSSA) on 6-h recordings of respiratory signals in rats. To validate MSSA as a respiratory signal analysis tool we tested it by detecting: breaths and breath-to-breath intervals; respiratory timing and volume modes; and changes in respiratory pattern caused by lesions of monoaminergic systems in rats. MSSA differentiated three respiratory timing (tachypneic, eupneic, bradypneic-apneic), and three volume (artifacts, normovolemic, hypervolemic-sighs) modes. Lesion-induced respiratory pattern modulation was visible as shifts in the distributions of monotone signal segment amplitudes, and of breath-to-breath intervals. Specifically, noradrenergic lesion induced an increase in mean volume (p ≤ 0.03), with no change of the mean breath-to-breath interval duration (p ≥ 0.06). MSSA of timing modes detected noradrenergic lesion-induced interdependent changes in the balance of eupneic (decrease; p ≤ 0.02), and tachypneic (an increase; p ≤ 0.02) breath intervals with respect to control. In terms of breath durations within each timing mode, there was a tendency toward prolongation of the eupneic (p ≤ 0.08) and bradypneic-apneic (p ≤ 0.06) intervals. These results demonstrate that MSSA is sensitive to subtle shifts in respiratory rhythmogenesis not detectable by simple respiratory pattern descriptive statistics. MSSA represents a potentially valuable new tool for investigations of respiratory pattern control. © 2008 Elsevier B.V. All rights reserved.",
journal = "Respiratory Physiology and Neurobiology",
title = "Monotone Signal Segments Analysis as a novel method of breath detection and breath-to-breath interval analysis in rat",
volume = "161",
number = "3",
pages = "273-280",
doi = "10.1016/j.resp.2008.03.001"
}

Bojić, T., Šaponjić, J., Radulovački, M., Carley, D. W.,& Kalauzi, A.. (2008). Monotone Signal Segments Analysis as a novel method of breath detection and breath-to-breath interval analysis in rat. in Respiratory Physiology and Neurobiology, 161(3), 273-280.
https://doi.org/10.1016/j.resp.2008.03.001

Bojić T, Šaponjić J, Radulovački M, Carley DW, Kalauzi A. Monotone Signal Segments Analysis as a novel method of breath detection and breath-to-breath interval analysis in rat. in Respiratory Physiology and Neurobiology. 2008;161(3):273-280.
doi:10.1016/j.resp.2008.03.001 .

Bojić, Tijana, Šaponjić, Jasna, Radulovački, Miodrag, Carley, David W, Kalauzi, Aleksandar, "Monotone Signal Segments Analysis as a novel method of breath detection and breath-to-breath interval analysis in rat" in Respiratory Physiology and Neurobiology, 161, no. 3 (2008):273-280,
https://doi.org/10.1016/j.resp.2008.03.001 . .