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Search Results: 1 - 10 of 1631 matches for " Mohamad Sawan "
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Fully On-Chip Integrated Photodetector Front-End Dedicated to Real-Time Portable Optical Brain Imaging  [PDF]
Ehsan Kamrani, Frederic Lesage, Mohamad Sawan
Optics and Photonics Journal (OPJ) , 2012, DOI: 10.4236/opj.2012.24037
Abstract:

Optical brain imaging using functional near infra-red spectroscopy (fNIRS) offers a portable and noninvasive tool for monitoring of blood oxygenation. In this paper we have introduced a new miniaturized photodetector front-end on achip to be applied in a portable fNIRS system. It includes silicon avalanche photodiodes (SiAPD), Transimpedance amplifier (TIA) front-end and Quench-Reset circuitry to operate in both linear and Geiger modes. So it can be applied for both continuous-wave fNIRS (CW-fNIRS) and also single-photon counting. Proposed SiAPD exhibits high-avalanche gain (>100), low-breakdown voltage (<12 V) and high photon detection efficiency accompanying with low dark count rates. The proposed TIA front-end offer a low power consumption (<1 mW), high-transimpedance gain (up to 250 MV/A), tunable bandwidth (1 kHz - 1 GHz) and very low input and output noise (~few fA/√Hz and few μV/√Hz). The Geiger-mode photon counting front-end also exhibits a controllable hold-off and rest time with an ultra fast quench-reset time (few ns). This integrated system has been implemented using submicron (0.35 μm) standard CMOS technology.

Design and Implementation Challenges of Microelectrode Arrays: A Review  [PDF]
Bahareh Ghane-Motlagh, Mohamad Sawan
Materials Sciences and Applications (MSA) , 2013, DOI: 10.4236/msa.2013.48059
Abstract:

The emerging field of neuroprosthetics is focused on design and implementation of neural prostheses to restore some of the lost neural functions. Remarkable progress has been reported at most bioelectronic levels—particularly the various brain-machine interfaces (BMIs)—but the electrode-tissue contacts (ETCs) remain one of the major obstacles. The success of these BMIs relies on electrodes which are in contact with the neural tissue. Biological response to chronic implantation of Microelectrode arrays (MEAs) is an essential factor in determining a successful electrode design. By altering the material compositions and geometries of the arrays, fabrication techniques of MEAs insuring these ETCs try to obtain consistent recording signals from small groups of neurons without losing microstimulation capabilities, while maintaining low-impedance pathways for charge injection, high-charge transfer, and high-spatial resolution in recent years. So far, none of these attempts have led to a major breakthrough. Clearly, much work still needs to be done to accept a standard model of MEAs for clinical purposes. In this paper, we review different microfabrication techniques of MEAs with their advantages and drawbacks, and comment on various coating materials to enhance electrode performance. Then, we propose high-density, three-dimensional (3D), silicon-based MEAs using micromachining methods. The geometries that will be used include arrays of penetrating variable-height probes.

Efficient hemodynamic states stimulation using fNIRS data with the extended Kalman filter and bifurcation analysis of balloon model  [PDF]
Ehsan Kamrani, Armin N. Foroushani, Mohsen Vaziripour, Mohamad Sawan
Journal of Biomedical Science and Engineering (JBiSE) , 2012, DOI: 10.4236/jbise.2012.511076
Abstract: This paper introduces a stochastic hemodynamic system to describe the brain neural activity based on the balloon model. A continuous-discrete extended Kalman filter is used to estimate the nonlinear model states. The stability, controllability and observability of the proposed model are described based on the simulation and measurement data analysis. The observability and controllability characteristics are in- troduced as significant factors to validate the preference of different hemodynamic factors to be considered for diagnosis and monitoring in clinical applications. This model also can be efficiently applied in any monitoring and control platform include brain and for study of hemodynamics in brain imaging modalities such as pulse oximetry and functional near infrared spectroscopy. The work is on progress to extend the proposed model to cover more hemodynamic and neural brain signals for real-time in-vivo application.
Detecting the Stable, Observable and Controllable States of the Human Brain Dynamics  [PDF]
Ehsan Kamrani, Armin N. Foroushani, Mohsen Vaziripour, Mohamad Sawan
Open Journal of Medical Imaging (OJMI) , 2012, DOI: 10.4236/ojmi.2012.24024
Abstract: A new technique is proposed in this paper for real-time monitoring of brain neural activity based on the balloon model. A continuous-discrete extended Kalman filter is used to estimate the nonlinear model states. The stability, controlla- bility and observability of the proposed model are described based on the simulation and measured clinical data analysis. By introducing the controllable and observable states of the hemodynamic signal we have developed a numerical tech- nique to validate and compare the impact of brain signal parameters affecting on BOLD signal variation. This model increases significantly the signal-to-noise-ratio (SNR) and the speed of brain signal processing. A linear-quadratic regulator (LQR) also has been introduced for optimal control of the model.
Hybrid Modeling Method for a DEP Based Particle Manipulation
Mohamed Amine Miled,Antoine Gagne,Mohamad Sawan
Sensors , 2013, DOI: 10.3390/s130201730
Abstract: In this paper, a new modeling approach for Dielectrophoresis (DEP) based particle manipulation is presented. The proposed method fulfills missing links in finite element modeling between the multiphysic simulation and the biological behavior. This technique is amongst the first steps to develop a more complex platform covering several types of manipulations such as magnetophoresis and optics. The modeling approach is based on a hybrid interface using both ANSYS and MATLAB to link the propagation of the electrical field in the micro-channel to the particle motion. ANSYS is used to simulate the electrical propagation while MATLAB interprets the results to calculate cell displacement and send the new information to ANSYS for another turn. The beta version of the proposed technique takes into account particle shape, weight and its electrical properties. First obtained results are coherent with experimental results.
A Polypyrrole-based Strain Sensor Dedicated to Measure Bladder Volume in Patients with Urinary Dysfunction
Sumitra Rajagopalan,Mohamad Sawan,Ebrahim Ghafar-Zadeh,Oumarou Savadogo
Sensors , 2008,
Abstract: This paper describes a new technique to measure urine volume in patients with urinary bladder dysfunction. Polypyrrole ¢ € “ an electronically conducting polymer - is chemically deposited on a highly elastic fabric. This fabric, when placed around a phantom bladder, produced a reproducible change in electrical resistance on stretching. The resistance response to stretching is linear in 20%-40% strain variation. This change in resistance is influenced by chemical fabrication conditions. We also demonstrate the dynamic mechanical testing of the patterned polypyrrole on fabric in order to show the feasibility of passive interrogation of the strain sensor for biomedical sensing applications.
A Polypyrrole-based Strain Sensor Dedicated to Measure Bladder Volume in Patients with Urinary Dysfunction
Sumitra Rajagopalan,Mohamad Sawan,Ebrahim Ghafar-Zadeh,Oumarou Savadogo,Vamsy P. Chodavarapu
Sensors , 2008, DOI: 10.3390/s8085081
Abstract: This paper describes a new technique to measure urine volume in patients with urinary bladder dysfunction. Polypyrrole – an electronically conducting polymer - is chemically deposited on a highly elastic fabric. This fabric, when placed around a phantom bladder, produced a reproducible change in electrical resistance on stretching. The resistance response to stretching is linear in 20%-40% strain variation. This change in resistance is influenced by chemical fabrication conditions. We also demonstrate the dynamic mechanical testing of the patterned polypyrrole on fabric in order to show the feasibility of passive interrogation of the strain sensor for biomedical sensing applications.
Energy-Optimal Electrical-Stimulation Pulses Shaped by the Least-Action Principle
Nedialko I. Krouchev, Simon M. Danner, Alain Vinet, Frank Rattay, Mohamad Sawan
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0090480
Abstract: Electrical stimulation (ES) devices interact with excitable neural tissue toward eliciting action potentials (AP’s) by specific current patterns. Low-energy ES prevents tissue damage and loss of specificity. Hence to identify optimal stimulation-current waveforms is a relevant problem, whose solution may have significant impact on the related medical (e.g. minimized side-effects) and engineering (e.g. maximized battery-life) efficiency. This has typically been addressed by simulation (of a given excitable-tissue model) and iterative numerical optimization with hard discontinuous constraints - e.g. AP’s are all-or-none phenomena. Such approach is computationally expensive, while the solution is uncertain - e.g. may converge to local-only energy-minima and be model-specific. We exploit the Least-Action Principle (LAP). First, we derive in closed form the general template of the membrane-potential’s temporal trajectory, which minimizes the ES energy integral over time and over any space-clamp ionic current model. From the given model we then obtain the specific energy-efficient current waveform, which is demonstrated to be globally optimal. The solution is model-independent by construction. We illustrate the approach by a broad set of example situations with some of the most popular ionic current models from the literature. The proposed approach may result in the significant improvement of solution efficiency: cumbersome and uncertain iteration is replaced by a single quadrature of a system of ordinary differential equations. The approach is further validated by enabling a general comparison to the conventional simulation and optimization results from the literature, including one of our own, based on finite-horizon optimal control. Applying the LAP also resulted in a number of general ES optimality principles. One such succinct observation is that ES with long pulse durations is much more sensitive to the pulse’s shape whereas a rectangular pulse is most frequently optimal for short pulse durations.
A suggested statistical approach for dealing with the non-significant interactions between treatments  [PDF]
Zakaria M. Sawan
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.35049
Abstract: A field experiment was conducted to study the effect of nitrogen (N) fertilizer and foliar appli-cation of potassium (K) and Mepiquat Chloride (MC) on yield of cotton. Seed cotton yield per plant and seed cotton and lint yield per hectare; have been increased due to the higher N rate and use of foliar application of K and MC. No significant interactions were found among the variables in the present study (N, K and MC) with respect to characters under investigation. Generally, interactions indicated that, the fa-vorable effects ascribed to the application of N; spraying cotton plants with K combined with MC on cotton productivity, were more obvious by applying N at 143 kg per hectare, and combined with spraying cotton plants with K at 957 g per hectare and also with MC at 48 + 24 g active ingredient per hectare. Sensible increases were found in seed cotton yield per hectare (about 40%) as a result of applying the same combination. However, this interaction did not reach the level of significance, so, statistical approach for dealing with the non-significant interactions between treatments, depending on the Least Significant Difference values has been suggested, to provide an opportunity to disclosure of the interaction effects regardless of their insignificance. As a matter of fact the original formula used in calculating the significance of interactions suffers a possible shortage, which can be eliminated through applying the new suggested formula.
Applied methods for studying the relationship between climatic factors and cotton production  [PDF]
Zakaria M. Sawan
Agricultural Sciences (AS) , 2013, DOI: 10.4236/as.2013.411A005
Abstract:

This study investigates the statistical relationship between climatic variables and aspects of cotton production (G. barbadense), and the effects of climatic factors prevailing prior to flowering or subsequent to boll setting on flower and boll production and retention in cotton. The effects of specific climatic factors during both pre- and post-anthesis periods on boll production and retention are mostly unknown. However, by determining the relationship of climatic factors with flower and boll production and retention, the overall level of production can be possibly predicted. Thus, an understanding of these relationships may help physiologists determine control mechanisms of production in cotton plants. Also, the study covers the predicted effects of climatic factors during convenient intervals (in days) on cotton flower and boll production compared with daily observations. Further, cotton flower and boll production as affected by climatic factors and soil moisture status has been considered. Evaporation, sunshine duration, relative humidity, surface soil temperature at 1800 h, and maximum air temperature, are the important climatic factors that significantly affect flower and boll production. The least important variables were found to be surface soil temperature at 600 h and minimum temperature. The five-day interval was found to be more adequately and sensibly related to yield parameters. Evaporation, minimum humidity and sunshine duration were the most effective climatic factors during preceding and succeeding periods on boll production and retention. There was a negative correlation between flower number and boll production and either evaporation or sunshine duration, while that correlation

with minimum relative humidity was positive. The soil moisture status showed low and insignificant correlation with flower and boll production. Higher minimum relative humidity, short period of sunshine duration, and low temperatures enhanced flower and boll formation.

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