Sharif Digital Repository

To investigate the role of biological processes in bacterial transport through poroud media, six rod shaped and motile bacteria were isolated from a crude oil sample. A multi stage screening procedure was utilized to select the most appropriate isolate in microbial enhanced oil recovery applications (MEOR). It was identified and registered as Bacillus licheniformis MS3 in GenBank database. After that, the physical properties and chemical structure of its biosurfactant were determined and it was proved to be a new lipopeptide biosurfactant which was called licheniformin. Power law logistic model was utilized to investigate the kinetics growth of the MS3 strain on insoluble carbon sources ... 

Moving of living organisms appears in many interesting problems, e.g. the growth of bacteria colonies, tumor growth, wound healing, color patterns of animals and etc. There are many ways to model such problems and PDE theory is widely used to investigate these problems. In this thesis, we study two well-known classic models. First, macroscopic “Keller–Segel” model and then kinetic “Othmer–Dunbar–Alt” System. Since these models have a nice behavior in two dimensions that they don’t have in other dimensions, we propose a way to alter them such that they behave in this way in all dimensions. Also none of the known models have the suitable dynamics in one dimension, so our model has the property... 

We Consider the Chemotaxi Systems in a smooth bounded domain as follow:{ █(ut = Δu-χ∇.(u∇v)+ f (u) x ϵ Ω ,t>0 @ @τ vt =Δv-v+u x ϵ Ω ,t>0)┤ Where χ∈ and f(u) =Au - Buα generalizes the logistic function with A≥0, B>0 and α>1. First for τ=0, global existence of such solutions for any nonnegative initial data is proved under the assumption that . Moreover, boundedness properties of the constructed solutions are studied. Next we assume that 2=α, τ>0 and we consider nonnegative solutions of the Neumann
Boundary value problem for the chemotaxis system above in a smooth bounded convex domain . We will see that if B is sufficiently large then for all sufficiently smooth initial data the... 

In the recent decade, researchers in the field of minimally invasive medicine have come up to the idea of utilizing micro organisms as smart micro robots. The advantage with this idea is the fact that problems such as energy supply and maneuvering are resolved for these sorts of micro swimmers. In this current work, a new numerical method for investigation of micro swimming is developed which is computationally efficient in characterizing locomotion of micro swimmers and using a finite element method software, locomotion of Paramecium has been investigated inside and outside a capillary tube. According to simulation results, it is possible to design a controlling system which is capable of... 

To generalize the Najafi_Golestanian swimmer model from one dimension to two dimensions and to demonstrate its chemotaxis ability, here we introduce a model that consists of four spheres with same radius connected by three arms and we call it a star swimmer. Each arm can be in two states, contracted and expanded (initial length). So that at the head of each arm there are molecular motors that can act as enzymes and as a result of chemical interaction with specific activating substances in their environment, cause the entire body of the tiny swimmer to move and rotate. The change in the concentration of the activating substance in the environment breaks the symmetry of the preferred state of...