אורית אישטיין

תלמידת המחלקה להנדסה ביו רפואית לתואר שני תרצה בנושא:

Walking through the Axoplasmic Jungle, a Cargo’s Perspective

Neurofilaments (NFs) lie parallel to the longitudinal axis of the axon. Their unique structure includes side-arms that protrude from the NF backbone and have a net charge. Due to their charge, side-arms of neighboring filaments form cross-links thereby forming a dense net-like structure that occupies most of the axon cytoplasm. Therefore, the net creates unavoidable obstacles for motor proteins, transporting essential cargos from one end of the axon to another. Since these cargos reach diameters much larger than the spaces within the net, the motor-cargo complex is expected to encounter these obstacles every few steps. Although there is an abundance of data today regarding the motor's mechanism of movement, the local reciprocal effect between the motor-cargo movement and its surrounding environment has not yet been modeled. For this purpose we developed a physical model in which two coping scenarios are proposed: (1) cross-links are modeled as barriers which require the motor to pay an energy penalty in order to break it. (2) The motor can stretch the cross-links which therefore constitute as an additional friction factor. Each option gives a different prediction regarding the different attributes of the motor-cargo movement such as the step size, step time etc.

Another aspect of the reciprocal effect between motor and environment is the question whether motor-cargo movement can cause sufficient drag force as to cause micro-streams in the intracellular fluid as detected in plant cells.

העבודה נעשתה בהנחיית דר' אורי נבו , המחלקה להנדסה ביו-רפואית, אוניברסיטת תל-אביב

אביחי רון

תלמיד המחלקה להנדסה ביו רפואית לתואר שני ירצה בנושא:

Monitoring bone mineral density (BMD) of the wrist –A parametric EIT simulation

Our goal is to validate the feasibility of monitoring wrist bone mineral density at home using a Parametric Electric Impedance Tomography (EIT) simulation.

Introduction: BMD testing is a vital component in the diagnosis and management of Osteoporosis. It is an excellent predictor for future fracture risk. Furthermore, deterioration of BMD in peripheral sites is a good predictor for fractures risk at the hip. Hip fractures are followed by an increased risk of future fractures. Approximately 20 percent of hip fracture patients require long-term nursing home care, and only 40 percent fully regain their pre-fracture level of independence.  

EIT is a Non-invasive bio-impedance measurement. The method is used for reconstructing the electrical and dielectric properties of the body. "Injected current method" uses surface electrodes array for current injection and potential measurement. By solving the backward problem by using a computerized model of the body we can then achieve a reconstruction. At high current frequencies we see a good correlation between the BMD of the bone and its electrical properties- conductivity [S/m] and Permittivity [F/m].

Methods: We solve the forward problem of the developing potential around the wrist due to current injection by using a Matlab numerical simulation of an adult human phantom (XCAT, Duke Uni.). The inverse problem is solved by building a lookup table of different bone densities which represent different disease stages.

Results: We examine the differences in potentials on the different electrodes between different stages of the disease. We found a high sensitivity for deterioration of the cortical bone, 80 percent change between a healthy stage (0.32 g\cm³ BMD) and Osteoporosis stage (0.16 g\cm³ BMD), 18 percent sensitivity for deterioration of the cancellous bone and 100 percent sensitivity for the simultaneous deterioration of both parts of the bones. The measurement is highly robust to electrical noises but the robustness to deposition of the electrode is limited to 1cm.

Conclusion: The technology may provide a simple method for evaluating changes in the BMD of the wrist.       

העבודה נעשתה בהנחיית פרופ' שמעון עבוד , המחלקה להנדסה ביו-רפואית, אוניברסיטת תל-אביב

ההרצאה תתקיים ביום ראשון 29.3.15, בשעה 14:15,

בחדר 315, הבניין הרב תחומי, אוניברסיטת תל אביב