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Full-Text Articles in Physics

Non Linear Optics For Materials Fabrication And Medical Instrumentation, Aurelio Paez Jan 2019

Non Linear Optics For Materials Fabrication And Medical Instrumentation, Aurelio Paez

Open Access Theses & Dissertations

Two-photon absorption is a nonlinear optical process where two photons are absorbed by a molecule simultaneously. The probability of this quantum phenomenon is proportional to the quadratic excitation of light intensity. It has many applications in biomedical and materials research, such as two-photon fluorescence microcopy. The first project is to apply two-photon absorption induced bond cleavage in photoreactive materials for engineering 3D tissue scaffolds. The major challenge for growing thick 3D tissues is the lack of vasculature, where nutrients and oxygen can be delivered to the growing cells. Our collaborators have synthesized a novel polypeptide that is composed of 34-mer ...


The Inverse And Direct Hofmeister Series Of Hen Egg White Lysozyme At Ph Below The Isoelectric Point (Pi) As Seen By Small Angle X-Ray Scattering(Saxs), Pawan Koirala Jan 2018

The Inverse And Direct Hofmeister Series Of Hen Egg White Lysozyme At Ph Below The Isoelectric Point (Pi) As Seen By Small Angle X-Ray Scattering(Saxs), Pawan Koirala

Open Access Theses & Dissertations

The structural changes of Hen Egg White Lysozyme (HEWL) in the intermediate stages leading up to Hofmeister anion-induced aggregation were measured using small-angle x-ray Scattering (SAXS). We used three concentrations of HEWL: 10mg/ml, 60mg/ml and 200mg/ml and two concentrations of salts: 0.1M and 1.0M, mostly in a Tris-buffer solution with a pH of 9.0. For 200mg/ml in Di-water solution, the scattering signal was best fit using an ellipsoidal form factor with equatorial radius of 28.4±0.1 Å and polar radius of 11.3±0.1 Å, and a screened Coulomb repulsive ...


Geant4 Study Of A Gamma Ray Collimator For Proton Therapy, Selim Romero Jan 2018

Geant4 Study Of A Gamma Ray Collimator For Proton Therapy, Selim Romero

Open Access Theses & Dissertations

This Thesis presents the results of an investigation of the use of collimators in proton therapy. The problem to solve is that in the proton therapy, we do not have the certainty if the target-tumor is receiving all the energy to destroy it or if we are really shooting at this one, so the remaining question is: where the beam is hitting? How to know it? to answer those questions our work has the propose of study proton therapy to determine where the proton interactions occur, these kinds of interactions usually produce gamma rays, and we simulated in GEANT4 the ...


Imaging Live Drosophila Brain With Two-Photon Fluorescence Microscopy, Syeed Ehsan Ahmed Jan 2017

Imaging Live Drosophila Brain With Two-Photon Fluorescence Microscopy, Syeed Ehsan Ahmed

Open Access Theses & Dissertations

Two-photon fluorescence microscopy is an imaging technique which delivers distinct benefits for in vivo cellular and molecular imaging. Cyclic adenosine monophosphate (cAMP), a second messenger molecule, is responsible for triggering many physiological changes in neural system. However, the mechanism by which this molecule regulates responses in neuron cells is not yet clearly understood. When cAMP binds to a target protein, it changes the structure of that protein. Therefore, studying this molecular structure change with fluorescence resonance energy transfer (FRET) imaging can shed light on the cAMP functioning mechanism. FRET is a non-radiative dipole-dipole coupling which is sensitive to small distance ...


Two-Photon Excitation Based Photochemistry And Neural Imaging, Kevin Andrew Hatch Jan 2016

Two-Photon Excitation Based Photochemistry And Neural Imaging, Kevin Andrew Hatch

Open Access Theses & Dissertations

Two-photon microscopy is a fluorescence imaging technique which provides distinct advantages in three-dimensional cellular and molecular imaging. The benefits of this technology may extend beyond imaging capabilities through exploitation of the quantum processes responsible for fluorescent events. This study utilized a two-photon microscope to investigate a synthetic photoreactive collagen peptidomimetic, which may serve as a potential material for tissue engineering using the techniques of two-photon photolysis and two-photon polymerization. The combination of these techniques could potentially be used to produce a scaffold for the vascularization of engineered three-dimensional tissues in vitro to address the current limitations of tissue engineering. Additionally ...


Study On Dioxygen Binding To Heme Using Scan Functional, Zegnet Yimer Muhammed Jan 2016

Study On Dioxygen Binding To Heme Using Scan Functional, Zegnet Yimer Muhammed

Open Access Theses & Dissertations

Density functional theory, a quantum mechanical based electronic structure method with GGA-PBE and MGG-SCAN functionals, are used to investigate the structure and energies of singlet, triplet, and quintet spin states of FeP (iron Porphyrin), FePIm (imidazole iron porphyrin), and FePImO2 (dioxygen imidazole iron porphyrin) systems. The binding and release of dioxygen to and from hemoglobin (Hb) are the most crucial reaction takes place in human body to sustain the existence of life. FePImO2 is used to model this phenomenon. When O2 binds to FePIm, the system undergoes a conformational change. i.e. from domed structure of FePIm in which the ...


Studying Cellular And Molecular Interaction With Two-Photon Fluorescence Microscopy, Arifur Rahaman Jan 2015

Studying Cellular And Molecular Interaction With Two-Photon Fluorescence Microscopy, Arifur Rahaman

Open Access Theses & Dissertations

Advances in microscopy and fluorescent probes provide new insight into studying cellular and molecular interactions. Two-photon fluorescence microscopy is one of the most important recent inventions in cellular and molecular study. This technology enables noninvasive study at cellular and molecular levels in three dimensions with submicrometer resolution. Two-photon excitation of fluorophores results from the simultaneous absorption of two photons. This excitation process has a number of unique advantages, such as reduced specimen photodamage and enhanced penetration depth. In this study, we used our two-photon microscope to observe predatorial behavior of fast moving bacterivorous marine organism Cafeteria roenbergensis and quantify Mycobacterium ...