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Photobiochemical changes in Chlorella g120 culture during trophic conversion (metabolic pathway shift) from heterotrophic to phototrophic growth regime
, Article Journal of Applied Phycology ; Volume 32, Issue 5 , 2020 , Pages 2807-2818 ; Ranglová, K ; Malapascua, J. R ; Torzillo, G ; Shayegan, J ; Silva Benavides, A. M ; Masojídek, J ; Sharif University of Technology
Springer Science and Business Media B.V
2020
Abstract
Physiological and photobiochemical changes and growth in the heterotrophic strain Chlorella vulgaris g120 were studied during trophic conversion from heterotrophic to phototrophic growth regime. After the exposure of the Chlorella g120 culture to light, it revealed a significant activity of the electron transport (450–700 μmol e− m−2 s−1 as measured by chlorophyll fluorescence) and high PSII photochemical yield Fv/Fm between 0.7 and 0.8. Fast fluorescence induction kinetics showed that PSII electron acceptors in the plastoquinone pool remained partly oxidized, indicating no downregulation of PSII electron transport. The data further revealed that high photobiochemical activity is lost in...
Modeling of Oxygen Transport and Exchange in an Acinus
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Saeed (Supervisor)
Abstract
An acinus is defined as the complex of airways supplied by one first order respiratory or transitional bronchiole. In this part, the replenishment of oxygen at the alveolar surface occurs by a combination of convective air flow with diffusion of oxygen in the air. So for studying gas exchange in the lung, modeling gas species transport and exchange in an acinus is important. Due to lacking direct measurements of the distribution of oxygen (or carbon dioxide) concentration in the acinus, several mathematical models have been developed and studied by numerical simulations. But in none of them the influence of breathing pattern and the role of blood flow in restricting the gas exchange rate have...
Extraction of Respiratory Information from ECG and Application on the
Apnea Detection
,
M.Sc. Thesis
Sharif University of Technology
;
Shamsollahi, Mohammad Bagher
(Supervisor)
Abstract
Respiration signal is one of the biological information required to monitor patient respiratory activities. Noninvasive respiratory monitoring is an extensive field of research, which has seen widespread interest for several years. It is well known that the respiratory activity influences electrocardiographic measurements (ECG) in various ways. Therefore, different signal processing techniques have been developed for extracting this respiratory information from the ECG, namely ECG derived respiratory (EDR). Potential advantages of such techniques are their low cost, high convenience and the ability to simultaneously monitor cardiac and respiratory activity. One of the aims of this thesis is...
Time-varying assessment of heart rate variability parameters using respiratory information
, Article Computers in Biology and Medicine ; Volume 89 , 2017 , Pages 355-367 ; 00104825 (ISSN) ; Zahedi, E ; Zarzoso, V ; Sharif University of Technology
Abstract
Analysis of heart rate variability (HRV) is commonly used for characterization of autonomic nervous system. As high frequency (HF, known as the respiratory-related) component of HR, overlaps with the typical low frequency (LF) band when the respiratory rate is low, a reference signal for HF variations would help in better discriminating the LF and HF components of HR. The present study proposes a model for time-varying separation of HRV components as well as estimation of HRV parameters using respiration information. An autoregressive moving average with exogenous input (ARMAX) model of HRV is considered with a parametrically modeled respiration signal as the input. The model parameters are...
ECG-derived respiration estimation from single-lead ECG using gaussian process and phase space reconstruction methods
, Article Biomedical Signal Processing and Control ; Volume 45 , 2018 , Pages 80-90 ; 17468094 (ISSN) ; Shamsollahi, M. B ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Respiratory activity influences electrocardiographic measurements (ECG) in various ways. Therefore, extraction of respiratory information from ECG, namely ECG-derived respiratory (EDR), can be used as a promising noninvasive method to monitor respiration activity. In this paper, an automatic EDR extraction system using single-lead ECG is proposed. Respiration effects on ECG are categorized into two different models: additive and multiplicative based models. After selection of a proper model for each subject using a proposed criterion, gaussian process (GP) and phase space reconstruction area (PSRArea) are introduced as new methods of EDR extraction for additive and multiplicative models,...
Modeling of the Cardiovascular System using Breathing Stimuli for Evaluation of the Autonomic Nervous System
, Ph.D. Dissertation Sharif University of Technology ; Zahedi, Edmond (Supervisor) ; Jehed, Mehran (Supervisor) ; Zarzoso, Vicente (Supervisor)
Abstract
Autonomic nervous system (ANS) controls involuntary activities of the body, e.g. heartbeat function and blood circulation. Common tests used for evaluation of the functionality of ANS system in regulation of the cardiovascular system include heart rate variability (HRV) analysis and studying the changes in heart rate or blood pressure during deep respiration, sit-to-stand or head-up tilt table test and Valsalva maneuver. Test parameters affect the amplitude of the variations of the cardiovascular signals. Therefore, in the recent years, analysis and modeling of the interaction between the relevant signals, e.g. heart rate, blood pressure and respiration, have been widely used for the...
Numerical and 1-D modeling of pulmonary circulation along with lumped parameter modeling of the heart
, Article 2013 20th Iranian Conference on Biomedical Engineering, ICBME 2013 ; December , 2013 , Pages 93-97 ; Firoozabadi, B ; Saidi, M. S ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
A one dimensional model of the pulmonary arterial network along with systemic circulation was introduced to quantify the human pulmonary artery hemodynamics. A lumped parameter model of the right ventricle was used as the inlet boundary condition. A time varying elastance related the volume and pressure of the right ventricle was imposed in the model. By using a four element Windkessel model, blood flow rate throughout the right ventricle was in hand. An asymmetric structured tree was chosen as the outlet boundary conditions. Simulation was based on solving one-dimensional equations of conservation of mass and momentum by using finite volume method. Blood flow rate, pressure and velocity...
Effects of geometric hystersis in lung deformation on irreversiblity in trajectories of fine inhaled particles
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010 ; Volume 1 , 2010 , Pages 789-796 ; 9780791849156 (ISBN) ; Saidi, M. S ; Sani, M ; Sharif University of Technology
Abstract
In order to perform the drug delivery via lung, tracking the trajectories of fine inhaled particles in the acinar airways is of high importance. The causes of irreversibility in the motion of fine particles (0.1 - 1 micron) and chaotic flow deep in the acinar region of lung has been always under investigation. In this study we demonstrate the importance of geometric hystersis and asynchrony of lung deformation on the issue. We adapted a 2D axisymmetric geometry of alveolated duct from recent relative works and deformed it in a way that some hystersis would appear in a respiration period. The overall deformation of duct was corresponding to the transpulmonary pressure of lung reported in...
Three Dimensional Fluid-structure Interaction Analysis of Air Flow and Inhaled Particle Transport in Human Pulmonary Alveoli
, Ph.D. Dissertation Sharif University of Technology ; Saeedi, Mohammad Saeed (Supervisor)
Abstract
The prediction of deposition efficiency of submicron particles in the pulmonary alveoli has received special attention due to its importance for drug delivery systems, and for assessing air pollutants health risks. In this work, the pulmonary alveoli of a healthy human are idealized by a three dimensional honeycomb like configuration and a fluid-structure interaction analysis is performed to study the normal cyclic breathing hydrodynamics. A viscoelastic model is used for the mechanical behavior of alveolar wall tissue. In contrast to previous works in which the inlet flow rate is predefined, in this model a negative pressure is imposed on the outside surface of the alveolus which causes air...
Efficient implementation of real-time ECG derived respiration system using cubic spline interpolation
, Article Proceedings - IEEE International Symposium on Circuits and Systems ; 2013 , Pages 1083-1086 ; 02714310 (ISSN) ; 9781467357609 (ISBN) ; Ehsani, S. P ; Shabany, M ; Sharif University of Technology
2013
Abstract
Monitoring the respiratory signal is crucial in many medical applications. Traditional methods for the respiration measurement are normally based on measuring the volume of air inhaled and exhaled by lungs (like spirometer) or oxygen saturation in blood. However, these methods have numerous challenges including their high cost and not being accessible in some cases. In this paper, an algorithm for deriving the respiratory signal from ECG signal is proposed, which is based on other proposed algotithms. This algorithm uses the cubic spline interpolation (CSI) of R-waves in ECG to derive the respiratory signal. The CSI algorithm is made efficient with respect to ECG features in order to reduce...
Mathematical modeling of heart rate and blood pressure variations due to changes in breathing pattern
, Article 2013 20th Iranian Conference on Biomedical Engineering, ICBME 2013, Tehran, 18 December 2013 through 20 December 2013 ; 2013 , Pages 54-58 ; Zahedi, E ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
Analysis of the heart rate (HR) variation due to respiration, known as respiratory sinus arrhythmia (RSA), is a method to assess the autonomic nervous system (ANS) function. In this paper a physiologically-based mathematical model consisting of the cardiorespiratory system and ANS control has been used in order to study the cardiovascular response (mean arterial blood pressure and HR) to breathing with different respiration rates and tidal volumes. Simulation results show that RSA has its maximal amplitude at the respiration frequency of 0.12 Hz and that RSA amplitude varies linearly by tidal volume. These results are in agreement with real data from the literature. In addition, the...
Drill string instability reduction by optimum positioning of stabilizers
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 224, Issue 3 , 2010 , Pages 647-653 ; 09544062 (ISSN) ; Behzad, M ; Rashed, G. R ; Sharif University of Technology
2010
Abstract
The main aim of this article is to find the optimum positions of the stabilizers that reduces the vibration and leads to the largest weight on bit (WOB) in drill strings. In this work, the potential energy of drill strings has been derived by considering the drill string weight and WOB. The potential energy of this continuous system is considered as a multi-degree-of-freedom system by the mode summation method. The equilibrium position of the system and its stability is determined by finding the roots of the first derivative and the sign of the second derivative of the potential energy, respectively. Using this formulation, the best positions of stabilizers that lead to the largest WOB can...
Modeling particle deposition in the respiratory system during successive respiratory cycles
, Article Scientia Iranica ; Volume 27, Issue 1 B , February , 2020 , Pages 215-228 ; Saidi, M. S ; Hosseini, V ; Sharif University of Technology
Sharif University of Technology
2020
Abstract
This study uses a 5-lobe symmetric model to investigate total, lobar and generational particle deposition fractions in the lungs during successive cycles. It was found that for the particle size between 0.05 and 2 μm and the tidal volumes greater than 1000 ml, the effect of successive cycles helped predict more deposition fraction per cycle up to about 16% than that of a single cycle. The mentioned range of tidal volumes corresponds to light or heavy physical activities. Therefore, it can be understood that people, when physically active, exposed to particulate matter within the mentioned size range are at higher health risk as compared to both the resting state and the same state...
Simulation of the effects of oxygen carriers and scaffold geometry on oxygen distribution and cell growth in a channeled scaffold for engineering myocardium
, Article Mathematical Biosciences ; Volume 294 , 2017 , Pages 160-171 ; 00255564 (ISSN) ; Mashayekhan, S ; Bastani, D ; Sharif University of Technology
Abstract
This study proposes a mathematical model to evaluate the impact of oxygen carriers and scaffold geometry on oxygen distribution and cell growth in a 3D cardiac construct using computational fluid dynamics (CFD). Flow equations, oxygen balance equation and cell balance equation were solved using special initial and boundary conditions. The modeling results revealed that 55% increase in cardiac cell density occurred by using 6.4% perfluorocarbon oxygen carrier (PFC) compared to pure culture medium without PFC supplementation. Moreover, the effects of the scaffold geometry on cell density were examined by changing the channel numbers and the construct length. A 30% increase in the average cells...
Prediction of particle deposition in the respiratory track using 3D-1D modeling
, Article Scientia Iranica ; Volume 19, Issue 6 , December , 2012 , Pages 1479-1486 ; 10263098 (ISSN) ; Dastanpour, R ; Saidi, M. S ; Pishevar, A. R ; Sharif University of Technology
2012
Abstract
Airflow simulation of the whole respiratory system is still unfeasible due to the geometrical complexity of the lung airways and the diversity of the length scales involved in the problem. Even the new CT imaging system is not capable of providing accurate 3D geometries for smaller tubes, and a complete 3D simulation is impeded by the limited computational resources available. The aim of this study is to develop a fully coupled 3D-1D model to make accurate prediction of airflow and particle deposition in the whole respiratory track, with reasonable computational cost and efficiency. In the new proposed method, the respiratory tree is divided into three parts to be dealt with using different...
A microfabricated platform for the study of chondrogenesis under different compressive loads
, Article Journal of the Mechanical Behavior of Biomedical Materials ; Volume 78 , 2018 , Pages 404-413 ; 17516161 (ISSN) ; Jahanbakhsh, A ; Saidi, M. S ; Bonakdar, S ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Microfluidic devices are beneficial in miniaturizing and multiplexing various cellular assays in a single platform. Chondrogenesis is known to pertain to chemical, topographical, and mechanical cues in the microenvironment. Mechanical cues themselves have numerous parameters such as strain magnitude, frequency, and stimulation time. Effects of different strain magnitudes on the chondrogenic differentiation of adult stem cells have not been explored thoroughly. Here, a new multilayer microdevice is presented for the unidirectional compressive stimulation of cells in a three-dimensional cell culture. Numerical simulations were performed to evaluate and optimize the design. Results showed a...
Rhythmic air-puff into nasal cavity modulates activity across multiple brain areas: A non-invasive brain stimulation method to reduce ventilator-induced memory impairment
, Article Respiratory Physiology and Neurobiology ; Volume 287 , 2021 ; 15699048 (ISSN) ; Salimi, M ; Nazari, M ; Garousi, M ; Tabasi, F ; Dehdar, K ; Salimi, A ; Jamaati, H ; Mirnajafi Zadeh, J ; Arabzadeh, E ; Raoufy, M. R ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Mechanical ventilation (MV) can result in long-term brain impairments that are resistant to treatment. The mechanisms underlying MV-induced brain function impairment remain unclear. Since nasal airflow modulates brain activity, here we evaluated whether reinstating airflow during MV could influence the memory performance of rats after recovery. Rats were allocated into two study groups: one group received rhythmic air-puff into the nasal cavity during MV and a control group that underwent ventilation without air-puff. During MV, air-puffs induced time-locked event potentials in OB, mPFC and vHPC and significantly increased the oscillatory activity at the air-puff frequency. Furthermore, in...