The emergence of biofilms:Computational and experimental studies

The response of biofilms to any external stimuli is a cumulative response aggregated from individual bacteria residing within the biofilm. The organizational complexity of biofilm can be studied effectively by understanding bacterial interactions at cell level. The overall aim of the thesis is to explore the complex evolutionary behaviour of bacterial biofilms. This thesis is divided into three major studies based on the type of perturbation analysed in the study. The first study analyses the physics behind the development of mushroom-shaped structures from the influence of nutrient cues in biofilms. Glazier-Graner-Hogeweg model is used to simulate the cell characteristics. From the study, it is observed that chemotaxis of bacterial cells towards nutrient source is one of the major precursors for formation of mushroom-shaped structures. The objective of the second study is to analyse the impact of environmental conditions on the inter-biofilm quorum sensing (QS) signalling. Using a hybrid convection-diffusion-reaction model, the simulations predict the diffusivity of QS molecules, the spatiotemporal variations of QS signal concentrations and the competition outcome between QS and quorum quenching mutant bacterial communities. The mechanical effects associated with the fluid-biofilm interaction is addressed in the third study. A novel fluid-structure interaction model based on fluid dynamics and structural energy minimization is developed in the study. Model simulations are used to analyse the detachment and surface effects of the fluid stresses on the biofilm. In addition to the mechanistic models described, a separate study is carried out to estimate the computational efficiency of the biofilm simulation models

Housekeeping inspection and inventory analysis are the primary responses of engineering and logistics operations in hospitality industry- An intensive case study of professional research on Sheraton Gateway Hotel in Toronto Pearson International Airport,

Housekeeping inspection maintains a chronological checklist and it has the major practice for the hospitality industry. Hospitality industry describes an imaging services to restaurants, lodging, event planning, theme parks, transportation, cruise line, tourism industry etc. Now days, hospitality as well as housekeeping are a dynamic and vibrant industry. It has different facilities of maintenances and direct operations with technology, engineering, housekeeping, kitchen workers, marketing, human resources, bartenders and supply chain logistic management

Englische Kunstmöbel : styl ausgang des XVIII jahrhunderts

Copia digital. España : Ministerio de Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 2018Fecha de ca. 1900 tomada del catálogo IDS Basel Bern, y del catálogo Österreichischer Bibliothekenverbun

Emergence of spatio-temporal variations in chemotherapeutic drug efficacy: in-vitro and in-Silico 3D tumour spheroid studies

Background: The mechanisms of action and efficacy of cisplatin and paclitaxel at cell population level are well studied and documented, however the localized spatio-temporal effects of the drugs are less well understood. We explore the emergence of spatially preferential drug efficacy resulting from variations in mechanisms of cell-drug interactions. Methods: 3D spheroids of HeLa-C3 cells were treated with drugs, cisplatin and paclitaxel. This was followed by sectioning and staining of the spheroids to track the spatio-temporal apoptotic effects of the drugs. A mechanistic drug-cell interaction model was developed and simulated to analyse the localized efficacy of these drugs. Results: The outcomes of drug actions on a local cell population was dependant on the interactions between cell repair probability, intracellular drug concentration and cell’s mitosis phase. In spheroids treated with cisplatin, drug induced apoptosis is found to be scattered throughout the volume of the spheroids. In contrast, effect of paclitaxel is found to be preferentially localized along the periphery of the spheroids. Combinatorial treatments of cisplatin and paclitaxel result in varying levels of cell apoptosis based on the scheduling strategy. Conclusions: The preferential action of paclitaxel can be attributed to the cell characteristics of the peripheral population. The model simulations and experimental data show that treatments initiated with paclitaxel are more efficacious due to the cascading of spatial effects of the drugs.Published versio

Computational Analysis of Turbulent Flow Around A Dimpled and smooth sphere

ABSTRACT Steady turbulent flow around a 43-mm diameter smooth sphere and one with 245 round dimples was simulated. The turbulent flow around the sphere was attained by placing a turbulator 9 mm's upstream of the center point. For comparison, the turbulator was also placed around the dimpled sphere. The simulation revealed stable vortical flow structure inside the dimples. A stable vortex pair in the wake region was predicted in both cases. Predicted separation point over the smooth sphere was further downstream than in the case of dimpled sphere. The predicted drag coefficient for the smooth sphere was 40 % lower than that of the dimpled sphere, which was 0.35. Drag predictions are compared with previously published measurements. INTRODUCTION There are many applications involving fluid flow over blunt bodies, and many examples can be seen in sports. A good example at hand is the golf ball, on which numerous investigations have been invested. Prior to the discovery of the effect of dimples, Tait [1] studied physics of golf balls through trajectories. After introducing dimples, studies continued on golf ball aerodynamics. Davies [2], for example, conducted measurements of lift and drag on golf balls using trajectories. Bearman and Harvey [3] used hexagonal and conventional-dimpled golf balls in their comprehensive wind-tunnel measurements of drag and lift on golf balls with various spin rates and Reynolds numbers. Smits and Smith [4] conducted similar measurements, and obtained an aerodynamic model to predict drag and lift over a given range of Reynolds numbers and spin rates. Recently, Kato et al. [5] conducted a numerical study on a spinning and non-spinning golf ball using a laminar flow model. While they aimed to capture drag reduction due to dimples, their results showed a drag increase on the golf ball, as compared to the smooth sphere. The increase in drag with dimples should have been anticipated since the drag decrease in golf balls is due to separation delay promoted by turbulence, which is triggered by dimples. Dimples on golf balls promote turbulence, the fluctuations of which energize the boundar

Convection and the Extracellular Matrix Dictate Inter- and Intra-Biofilm Quorum Sensing Communication in Environmental Systems.

The mechanisms and impact of bacterial quorum sensing (QS) for the coordination of population-level behaviors are well studied under laboratory conditions. However, it is unclear how, in otherwise open environmental systems, QS signals accumulate to sufficient concentration to induce QS phenotypes, especially when quorum quenching (QQ) organisms are also present. We explore the impact of QQ activity on QS signaling in spatially organized biofilms in scenarios that mimic open systems of natural and engineered environments. Using a functionally differentiated biofilm system, we show that the extracellular matrix, local flow, and QQ interact to modulate communication. In still aqueous environments, convection facilitates signal dispersal while the matrix absorbs and relays signals to the cells. This process facilitates inter-biofilm communication even at low extracellular signal concentrations. Within the biofilm, the matrix further regulates the transport of the competing QS and QQ molecules, leading to heterogenous QS behavior. Importantly, only extracellular QQ enzymes can effectively control QS signaling, suggesting that the intracellular QQ enzymes may not have evolved to degrade environmental QS signals for competition