Sharif Digital Repository

In this thesis, a cellular model of electroporation process and its detection by ultrasound signals is proposed. Electroporation is permeabilization of the cell membrane, caused by an external electric field. The resulted pores open cell’s membrane to large or hydrophilic molecules. The process of Electroporation has been used in Gene therapy and treatment of solid tumors. In this project, first we made a phantom of electroporated tissue and a phantom of normal tissue and then we simulated their responses to a linear array ultrasound transducer. By comparision of received signals from phantoms the probable effect of electroporation on ultrasound RF signals revealed. Results show up to 5 %... 

Nowadays, all of the devices that measure blood pressure commercially at home are using wrist or arm cuffs preventing the systolic or diastolic blood pressure from being measured continuously. Various parameters such as blood flow with some degree of correlation with blood pressure that can be measured noninvasively have been suggested. However, these parameters do not produce accurate estimates for blood pressure. Pulse Transit Time (PTT) which is defined as the interval between the R peak of ECG signal and the next PPG signal valley has shown to have over 90% correlation with systolic blood pressure in past studies. In this thesis, the relationship between the value of the systolic blood... 

Routine ultrasound calibration methods have some restrictions such as: low bandwidth, low frequency resolution, limited spatial resolution, the high cost of test and risk of damage to the transducer when exposed to high powers. In this thesis, a new technique based on microbubble resonance is proposed. Non-linear resonating microbubbles produce harmonics;the first harmonic may be masked by reflection from larger microbubbles as well as unwanted reflections which cause ambiguity in the determination of the amplitude of the excited pressure. Therefore, the second harmonic is used, with a single characteristic peak. In order to model the physical phenomenon, the second harmonic generated in the... 

Measuring the human brachial arterial diameter has significant applications in medical research. This is conventionally carried out using ultrasonography which is costly and operator-skill dependent. The objective of this project is to come up with substitute solutions based on optical measurement. Reflectance photoplethysmography (PPG) over the radial artery has been considered to this end. Monte Carlo method has been employed to simulate light propagation in the wrist area, along with a model comprising tissue, artery and bone, made of simple solid geometries. Functions of optical parameters such as refractive index, absorption coefficient, scattering coefficient and anisotropy factor have... 

Inability of endothelial cells in responding to metabolic needs (endothelial dysfunction,) is a sign of heart diseases like atherosclerosis and vascular stenosis. Recently, a new method using finger PPG signal has been proposed to determine endothelial function in response to reactive hypertension (RH.) PPG-based endothelial function assessment results are not fully correlated with ultrasound FMD tests, and this is because of some auto-regulation phenomena in the fingertip. It is expected that such problems will not exist in larger arteries, like the radial artery. The goal of this project is to acquire the PPG signal from the radial artery as it is proportional to blood volume changes in... 

Vaccination is one of the ways of disease control and prevention, which not only protect individuals against the disease, but also reduce the disease spread rate. Mass vaccination of individuals is not always possible due to the high cost and limitation of immunization resources. Therefore, researchers are always seeking solutions to find the persons that their immunization may have a greater impact in reduction of disease spread rate. The advent of network epidemic models and the possibility of removal the secured nodes in those models, showed that this problem is equivalent to finding a limited set of individuals that their removal will eliminate or minimize the number of people at risk of... 

In quantum mechanics, every system is described by a state function. The state function determines the probability of different outcomes of a certain measurement which is performed on the physical system. The connection between uncertainties about different measurements is presented by inequalities best known as Heisenberg’s uncertainty inequality. In face, the uncertainty relations state that there exist incompatible measurements, to which the outcomes of measurements cannot be predicted simultaneously. Although the uncertainty relations can be inferred from mathematical formalism of quantum mechanics, there is a profound relationship with other aspects of physics. Here we investigate the... 

Ultrasonic assisted grinding is a novel method for improving the grinding process of difficult-to-cut materials. In the present research a novel set-up has been designed and manufactured for utilizing ultrasonic vibrations in cylindrical grinding. The designed ultrasonic head vibrates a rotating workpiece in axial direction. An alumina-zirconia ceramic (AZ90) has been selected as the workpiece material. Energy aspects and workpiece surface characteristics of ultrasonic assisted cylindrical grinding (UACG) and conventional cylindrical grinding (CG) processes have been analytically modeled and corresponding grinding experiments have been performed. The combined kinematics of the cylindrical...