Strain Estimation of Fibronectin Fibrils Using Two Dimensional Digital Image Correlation

Title from PDF of title page, viewed on June 15, 2015Thesis advisor: Ganesh ThiagarajanVitaIncludes bibliographic references (pages 64-67)Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2014Bone consists of a highly specialized mineralized extracellular matrix (ECM) which supports cells and tissues. Fibronectin is a non-collagenous protein produced by bone cells and is one of the earliest ECM proteins to be assembled. Fibronectin supports the assembly of several other bone matrix proteins, therefore understanding the dynamic process by which the fibronectin is assembled provides insight into how the bone matrix is formed. Live cell imaging of fibronectin assembly in living osteoblasts helps in understanding the kinematics of its assembly, which is a highly dynamic process. Fibronectin assembly was imaged in 2T3 osteoblasts using time lapse imaging over a 48 hour period. This was divided into four equal 12 hour stages, in which we could observe the assembly process from no fibrils to formation of a mature fibril network. Two Dimensional Digital Image Correlation (2D-DIC), a powerful optical computational tool, was used to quantify the tensile and compressive strains experienced by the assembling fibronectin fibrils due to the extensive cell motion. The 2D-DIC technique was used to quantify the total lengths, large strains and displacements of the assembling fibronectin fibrils. All the code has been developed using Matlab version 12. Seven iv different movie stacks from two experiments were analyzed. The results quantify the strains experienced by the fibrils at different time stages, due to the underlying cell motion. The average tensile and compression strains were reduced by 6,000με in the12- 24hr movie segment compared to 24-36hr. The average tensile strain was decreased by 6,000 με and the average compression strain was decreased by 3,000με in the 24-36hr movie segment compared to 36-48hr. This suggests that fibril strains are reduced as a consequence of matrix maturation. Individual fibrils also showed unique strain profiles, illustrating both the dynamic nature and heterogeneity of fibril motions. This thesis signifies the importance of fibronectin protein in the ECM assembly process by providing strong mathematical and statistical details obtained using the Digital Image CorrelationIntroduction -- Development of the DIC algorithm form measuring fibronectin fibril strains during assembly -- Parametric analysis -- Results and future wor

A cross sectional study on severe acute maternal morbidity near-miss at tertiary care centre in Hyderabad, Telangana, India

Background: A maternal near-miss case is defined by World Health Organization (WHO) as “a woman who nearly died but survived a complication that occurred during pregnancy, childbirth or within 42 days of termination of pregnancy.” Severe acute maternal morbidity (SAMM) is the acronym for the more popular term of ‘near-miss’ cases. There are approximately 118 life threatening events of “near miss mortality” or SAMM for each maternal death. Analysing near miss cases can prevent maternal death.Methods: It is a retrospective study based on medical records. Sample size is all the pregnant cases admitted in Department of Obstetrics and Gynecology in AIMSR, Hyderabad, Telangana, India over the period of January 2015- June 2017 (two and half years) i.e. 2276. All records were gathered and each record that satisfy near miss criteria/maternal mortality were segregated, data has been collected on the occurrence of severe pregnancy-related complications or those who require critical interventions and admission to intensive care unit as per the proforma (according to WHO near miss questionnaire). Data entry done in MS Excel and analyzed using Epi Info.Results: Total MNM/SAMM patients were 85 out of 2276 pregnant women (3.7%). The duration of the stay, potential life-threatening conditions (PTLC), critical interventions, organ dysfunctions, mode of delivery, treatment for PPH, hypertensive disorders and associated conditions among SAMM patients were calculated. SAMM patients who has severe post-partum hemorrhage PPH were 24.7%, severe pre-eclampsia was 31.7%, eclampsia was 2.4%, patients with both severe PPH and eclampsia were 2.4%.Conclusions: Near misses can be prevented to some extent by spreading awareness about possible obstetric complications and risk stratification. The WHO tool for analysis of maternal near miss or SAMM can identify more preventable causes of maternal death. Prospective monitoring of maternal morbidity may be useful in identifying determinants of severe maternal mortality

Nanoscale Ductile Mode Ultraprecision Cutting of Potassium Di Hydrogen Phosphate

Master'sMASTER OF ENGINEERIN

New Concepts for Gelation of Alginate and its Derivatives

Bioengineering applications require materials that offer tunable and precise control over material properties. In particular, hydrogels of the polysaccharide, alginate have been widely studied for applications such as drug-delivery vehicles, matrices for encapsulation of cells, and scaffolds for tissue engineering. The ability of alginate to form a physically cross-linked hydrogel under mild conditions is a key factor for many applications. Traditionally, alginate gelation has been induced by the addition of divalent ions like calcium (Ca2+). In this work, we explore new ways to induce gelation of alginate or its derivatives. These new routes are of interest because they can allow researchers to circumvent current limitations and moreover they can also enable new applications. Three new concepts are explored: (1) ionic gelation activated by light; (2) ionic gelation activated by an enzyme and its substrate; (3) gelation of hydrophobically modified alginate mediated by biological cells. In our first study, we demonstrate a concept for ionic gelation of alginate in response to light, which enables us to create chemically erasable and spatially selective patterns of alginate gels. We impart light responsiveness by combining alginate, an insoluble calcium vector (e.g., CaCO3) and a light responsive component, viz. a photoacid generator (PAG). Upon UV irradiation, the PAG dissociates to release H+ ions, which react with the CaCO3 to generate free Ca2+ in-situ. In turn, the Ca2+ ions cross-link the alginate to form a gel. We show photopatterning of alginate gels, which are used to entrap contents (e.g., microparticles) and subsequently release them by a Ca2+ chelator. In our second study, we demonstrate enzymatic gelation of alginate. Here, we use an enzyme/substrate reaction to generate H+ ions. The components of our system are glucose oxidase (GOx, enzyme), glucose (substrate), alginate and CaCO3. First, GOx catalyzes oxidation of glucose to generate H+ ions. These H+ ions solubilize CaCO3 and release free Ca2+ ions in-situ. In turn, Ca2+ ions cross-link alginate chains into a gel. A sol-gel transition is observed only when GOx senses and catalyzes glucose. By exploiting the specificity of the enzyme for its substrate, we use this concept to build a visual test for the presence of glucose in an unknown product. In our final study, we induce gels by combining a hydrophobically modified (hm) derivative of alginate with biological cells. Gelation occurs due to hydrophobic interactions between the grafted hydrophobes and the bilayers of biological cells. The polymer chains thus get attached to the cells and bridge the cells into a three-dimensional network. This gelation can also be reversed (to release the cells) by addition of a supramolecule, α-cyclodextrin, which has a hydrophobic binding pocket that binds to the hydrophobes. Cell gelation by hm-alginate may be useful in cell culture and tissue engineering applications. As a step towards these potential applications, we show that the process of gelation by hm-alginate is benign to the cells

Machine-Learning-Based Exploration of Bending Flexoelectricity in Novel 2D Van der Waals Bilayers

Accurate examination of electricity generation stemming from higher-order deformation (flexoelectricity) in 2D layered materials is a highly challenging task to be investigated with either conventional computational or experimental tools. To address this challenge herein an innovative and computationally efficient approach on the basis of density functional theory (DFT) and machine-learning interatomic potentials (MLIPs) with incorporated long-range interactions to accurately investigate the flexoelectric energy conversion in 2D van der Waals (vdW) bilayers is proposed. In this approach, short-range interactions are accurately defined using the moment tensor potentials trained over computationally inexpensive DFT-based datasets. The long-range electrostatic (charge and dipole) and vdW interaction parameters are calibrated from DFT simulations. Elaborated comparison of mechanical and piezoelectric properties extracted from the herein proposed approach with available data confirms the accuracy of the devised computational strategy. It is shown that the bilayer transition metal dichalcogenides can show a flexoelectric coefficient 2–7 times larger than their monolayer counterparts. Noticeably, this enhancement reaches up to 20 times for Janus diamane and fluorinated boron-nitrogen derivatives of diamane bilayers. The presented results improve the understanding of the flexoelectric effect in vdW heterostructures and moreover the proposed MLIP-based methodology offers a robust tool to improve the design of novel energy harvesting devices. © 2022 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH

Highly anisotropic mechanical and optical properties of 2D NbOX2 (X = Cl, Br, I) revealed by first-principle

In the latest experimental success, NbOI2 two-dimensional (2D) crystals with anisotropic electronic and optical properties have been fabricated (Adv. Mater. 33 (2021), 2101505). In this work inspired by the aforementioned accomplishment, we conduct first-principles calculations to explore the mechanical, electronic, and optical properties of NbOX2 (X = Cl, Br, I) nanosheets. We show that individual layers in these systems are weakly bonded, with exfoliation energies of 0.22, 0.23, and 0.24 J m-2, for the isolation of the NbOCl2, NbOBr2, and NbOI2 monolayers, respectively, distinctly lower than those of the graphene. The optoelectronic properties of the single-layer, bilayer, and bulk NbOCl2, NbOBr2, and NbOI2 crystals are investigated via density functional theory calculations with the HSE06 approach. Our results indicate that the layered bulk NbOCl2, NbOBr2, and NbOI2 crystals are indirect gap semiconductors, with band gaps of 1.79, 1.69, and 1.60 eV, respectively. We found a slight increase in the electronic gap for the monolayer and bilayer systems due to electron confinement at the nanoscale. Our results show that the monolayer and bilayer of these novel 2D compounds show suitable valence and conduction band edge positions for visible-light-driven water splitting reactions. The first absorption peaks of these novel monolayers along the in-plane polarization are located in the visible range of light which can be a promising feature to design advanced nanoelectronics. We found that the studied 2D systems exhibit highly anisotropic mechanical and optical properties. The presented first-principles results provide a comprehensive vision about direction-dependent mechanical and optical properties of NbOX2 (X = Cl, Br, I) nanosheets