Physics Commons^™

Study Of Blinking Statistics In Silver Coated Cobalt Ferrite Single Nanoprticle Using Two-Photon Fluorescence Microscopy, Rajen Kumar Goutam

Open Access Theses & Dissertations

Two-photon fluorescence microscopy is a powerful tool to study the molecular and cellular interactions. This technology is a non-invasive approach with the advantage of three-dimensional imaging up to submicron resolution. Two-photon excitation process is the result of simultaneous absorption of two photons that has special features of reduced photodamaged and elongated penetration depth on samples. In this work, blinking statistics of silver-coated Cobalt ferrite (CoFe2O4) single nanocrystal is studied using two-photon fluorescence microscopy. By defining the intensity threshold, the observed fluorescence is divided into two distinct stages: OFF and ON states. Both of these states followed the inverse power law. …

Phase Diagram Of Nuclear Matter, Adrian Gaytan Terrazas

Open Access Theses & Dissertations

Nowadays it is well known that nuclear matter has a liquid and a gas phase, as well as a coexistence of phases region. Symmetric nuclear matter (same number of protons and neutrons) exhibit phase transitions from the gas phase to a liquid-gas mixture. A useful tool to represent such phases and transitions is through diagrams that show the necessary conditions of density and temperature to be in either of the phases.

Now the question is, what if we extend the traditional phase diagram for symmetric matter to the asymmetric

cases (different number of protons and neutrons)?

This study uses classical …

Near Room Temperature Magnetocaloric Materials For Magnetic Refrigeration, Eduardo Martinez Teran

Open Access Theses & Dissertations

Magnetic refrigeration (MR) is a cooling process based on the magnetocaloric effect (MCE) that is present to some extent in all magnetic materials, and the ones in which this effect is more appreciable are called magnetocaloric materials (MCM). The implementation of new designs and materials for the construction of cooling systems is a must do, being essential that these improved designs will reduce the environmental impact and increase the efficiency of their predecessors. In this thesis, the magnetocaloric effect theory is presented from a thermodynamic point of view and also the synthesis and study to a new Heusler alloy (MnFe2Ga) …

Computational Studies On Perovskite-Metallofullerene Interface And Magnetic Properties Of Mn-Based Mixed Olivines, Bethuel Omutiti Khamala

Open Access Theses & Dissertations

Methyl ammonium lead halide (MAPbX3) perovskite based solar cells have recently emerged as promising class of materials for photovoltaic applications with efficiencies reaching over 22%. Designing interfaces with strong binding is vital to developing efficient, high-performing solar cells. Fullerene-based materials are widely employed as efficient electron acceptors and can serve as electron transporting layer in perovskite based solar cells. We have studied interfaces of methyl ammonium lead iodide MAPbI3 with Sc3N@C80 fullerene and Sc3N@C80PCBM fullerene derivate within the density functional formalism. Different surface terminations and orientations of the methyl ammonium are examined for binding of the fullerene layer. Our calculated …

Spectroscopic Analysis Of Calcium Oxalate Kidney Stone Inhibition By Nordihydroguaiaretic Acid (Ndga), Mahendra Subedi

Open Access Theses & Dissertations

This current study provides information regarding the inhibition of calcium oxalate type of kidney stones by the use of nordihydroguaiaretic acid (NDGA). Around 80% of kidney stones found in patients are principally made of calcium oxalate and calcium phosphate. NDGA is an antioxidant compound that is chemically extracted from the desert bush Larrea tridentata. This work is a logical continuation of a previous research, where different concentrations of Larrea tridentata extract were used for such inhibition. Size and morphological changes from a calcium oxalate monohydrate (COM) structure to a calcium oxalate dihydrate (COD) structure were previously reported.

In the current …

A Study Of Solvent Effects On The Ground And Excited States Of Endohedral Tri-Scandium Nitride C80 Fullerene Coupled With Zinc Phthalocyanine And Metal-Free Phthalocyanine Using Dft-Pcm Method, Timilsina Prasad Timlsina

Open Access Theses & Dissertations

The photovoltaic active materials composed of endohedral metafullerene and phthalocyanine derivatives are known as excellent electron donor-acceptor pairs. The tri-metallic nitride endohedral C80 fullerene exhibits high absorption coefficients in the visible region of the spectrum and has similar electron-accepting abilities as that of C60 fullerene, which can allow for higher efficiencies in OPV devices. In this study, we examine the effect of solvent on the charge transfer excitation energies of Sc3N@C80-ZnPc and Sc3N@C80-H2Pc donor-acceptor molecular complexes. Three different solvents with different polarity - water, toluene, and acetone are used. The solvent is modeled as a polarizable continuum as implemented in …

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 …

Quasi-Harmonic And Anharmonic Entropies In Transition Metals, Bimal K C

Open Access Theses & Dissertations

Density functional theory (DFT) employing the quasi-harmonic approximation (QHA) is a robust method for evaluating thermal properties of solids. In the case of transition metals however, the method yields high values of the thermal pressure when compared to experimental data or with more direct methods like quantum-molecular dynamics (QMD) simulations. Surprisingly, there has not been to date, a systematic study aimed at understanding the reasons for these large discrepancies, particularly at low temperature, i.e. below the Debye temperature of the solid. Using Tantalum as a test model for which a lot of experimental data exist, thermal properties were evaluated employing …

Magnetic Nanoparticles For Hyperthermia For Cancer Treatment, Bianca Paola Meneses Brassea

Open Access Theses & Dissertations

Fe3O4 and NixCu4-x magnetic nanoparticles were synthesized using supercritical conditions of liquids and wet chemistry, respectively. Characterization methods (VSM, SEM, TEM, and magnetic hyperthermia) yielded results that prove feasibility for magnetic hyperthermia for cancer treatment.

Dimensionality Of Magnetism In Trirutile Cota2o6 And Its Derivatives, Raju Baral

Open Access Theses & Dissertations

In this thesis, we addressed the question of low dimensionality of trirutile compound CoTa2O6 and studied how the low dimensionality evolved with doping of Mg on Co-site. In order to study low dimensionality in CoTa2O6 and its derivative compounds Co1-xMgxTa2O6 (x = 0.1, 0.3, 0.5, 0.7, and 1), we used different techniques: X-ray diffraction, magnetic susceptibility, magnetization, specific heat and elastic neutron diffraction. We have addressed the question of low dimensional magnetism of CoTa2O6 by preparing phase-pure samples of the compound. In CoTa2O6 a broad feature is observed in magnetic susceptibility at 10 K and an antiferromagnetic phase transition is …

Study Of D-Electron Systems With Fermi-Lowdin Orbital Self-Interaction Correction, Prakash Mishra

Open Access Theses & Dissertations

Density Functional Theory (DFT) is one of the very popular and versatile methods for calculations to study electronic structure, and the accuracy of DFT depends on the approximation used in the exchange-correlation functional. One of the known problems with the approximation is that the widely used density functional approximations (DFA) suffer self-interaction errors. Systems with d-electrons such as transition metal oxides often show deviation of DFT predicted behavior from experimental result. SIE tends to unphysically lower the energies of fractionally occupied state which leads to deviation from piece-wise linear behavior of total energy between two integer occupations. This leads to …

Novel Maximum Entrophy Method For The Average Survival Time Differences Between Two Groups, Joscelyne Guzman - Gonzalez

Open Access Theses & Dissertations

We suggest a Maximum Likelihood estimator for the Average Survival Time Difference between two groups, based on the extra time in which should be added to one group to produce the maximum entropy of the result. The estimator is calculated only from time to event data, does not assume hazard proportionality and provides directly the magnitude of the clinical differences between the groups. Our Monte Carlo simulations show that, even at low sample numbers the estimator is a reliable predictor for the clinical differences between the groups, and therefore can be used to estimate from preliminary data whether or not …

Nonlinear Optics For Nanoparticle Tracking And Materials Characterization, Angela Christina Aguilar

Open Access Theses & Dissertations

A high-speed 3D imaging method is developed by integrating ultrafast laser pulse shaping, temporal focusing microscopy and defocused imaging. This system does not require mechanical movement of either the stage or laser beam. Axial scanning is achieved by manipulation of group velocity dispersions on the femtosecond laser spectrum via pulse shaping method by applying modulation functions on an acoustic optical modulator which diffracts the laser spectrum. The scanning depth becomes only dependent on electronic signals which can be tuned to kHz speeds. The volumetric high-speed scanning capability was demonstrated on fluorescent microspheres suspended in a volume of 100 x100 x …

Using Two-Photon Microscopy To Analyze Arabidopsis Thaliana Leaves Under Autophagy Conditions And Second Harmonic Generation In Collagen, Andres Martin Reyes

Open Access Theses & Dissertations

Two-photon microscopy has emerged as a highly efficient and effective imaging tool for biological samples. This can be utilized in studying recently emerging technologies and conditions such as the autophagy process in arabidopsis thaliana leaves and second harmonic generation in collagen. Both of these areas of study utilize the two-photon microscopy practice effectively in uncovering more information of the biological nature of examined samples.

Electron Binding Energy Of Polar Molecules Using Fermi Löwdin Orbital Self Interaction Corrected Density Functional Scheme, Peter Obinna Ufondu

Open Access Theses & Dissertations

Density functional theory (DFT) has become a standard method for electronic structure calculations in physics. The standard approximate density functional usually do not bind this class of anions, due to self-interaction error (SIE). We apply the recently developed Fermi Löwdin orbitals based self-interaction correction method (FLOSIC) with long-range diffuse Gaussian functions to study dipole bound anions and negatively charged water clusters. These calculations are carried out using Perdew-Wang (1992) local spin density PW91-LDA, Perdew-Burke-Ernzerhof PBE-GGA, and the recently developed Strongly Constrained and Appropriately Normed SCAN-meta-GGA functional which satisfies all the known constraints for exchange-correlation functional. Plot from FLOSIC density difference …