Physics Commons^™

A Review On Antibacterial Activity Of Nanoparticles, Badr-Edine Sadoq, Mohammed Reda Britel, Adel Bouajaj, Ramzi Maâlej, Ahmed Touhami, Marwa Abid, Hanen Douiri, Fakhita Touhami, Amal Maurady

Physics and Astronomy Faculty Publications and Presentations

The increasing resistance of bacteria to antibiotic agents is a main global public health problem. The use of nanoparticles is one of the promising ways to overcome microbial resistance to antimicrobial agents. Metal nanoparticles are increasingly used to target bacterial strains. Advances in nanotechnology, in particular the ability to synthesize nanoparticles of specific size and shape, are likely to lead to the development of new antibacterial agents. The antibacterial activities of nanoparticles are largely influenced by their sizes and large surface area/mass ratio. The antibacterial mechanisms of nanoparticles are poorly understood, but the currently accepted mechanisms include oxidative stress induction, …

Signatures Of Black Holes, Alexandra B. Chanson

All Graduate Theses and Dissertations

In this defense I will describes three approaches to learn more about the relationship between the dynamics of black-holes and the distinctive signatures of a black hole systems: infinitesimal changes in the black hole background producing field excitations relating new fundamental black hole thermodynamic relations, mechanisms powering relativistic black hole jets and spontaneous symmetry breaking in five space-time dimensions, and physical signatures of black hole event horizons as conformal field theory duals (in both d=4,5 dimensional axisymmetric spacetimes).

The Influence Of Allostery Governing The Changes In Protein Dynamics Upon Substitution, Joseph Hess

All Dissertations

The focus of this research is to investigate the effects of allostery on the function/activity of an enzyme, human immunodeficiency virus type 1 (HIV-1) protease, using well-defined statistical analyses of the dynamic changes of the protein and variants with unique single point substitutions ¹. The experimental data¹ evaluated here only characterized HIV-1 protease with one of its potential target substrates. Probing the dynamic interactions of the residues of an enzyme and its variants can offer insight of the developmental importance for allosteric signaling and their connection to a protein’s function. The realignment of the secondary structure elements can …

Spectral Broadening Effects On Pulsed-Source Digital Holography, Steven A. Owens, Mark F. Spencer, Glen P. Perram

Faculty Publications

Using a pulsed configuration, a digital-holographic system is setup in the off-axis image plane recording geometry, and spectral broadening via pseudo-random bit sequence is used to degrade the temporal coherence of the master-oscillator laser. The associated effects on the signal-to-noise ratio are then measured in terms of the ambiguity and coherence efficiencies. It is found that the ambiguity efficiency, which is a function of signal-reference pulse overlap, is not affected by the effects of spectral broadening. The coherence efficiency, on the other hand, is affected. As a result, the coherence efficiency, which is a function of effective fringe visibility, is …

The Derivation Of Sodium Density In The Mesosphere And Lower Thermosphere From The Na Lidar Photon Counting Profiles, Xiaoqi Xi

All Graduate Theses and Dissertations

Derivation of Sodium (Na) number density from the Na lidar observations requires the in situ temperature and wind information because the absorption cross-section of the Na atom is a function of these dynamic parameters. The Na number density above ~ 110 km altitude was difficult to derive with the conventional algorithm, however. The standard output of the Na number density that utilizes the lidar-measured wind and temperature information falls short at ~ 110 km altitude and above due to the relatively large measurement uncertainties in the two critical parameters (low signal-to-noise ratio). Therefore, an innovative algorithm that may drive the …

Size Effect On The Optical Response Of Cylindrical Palladium Nanoparticles, Salem Marhaba, Mohammed Khalaf

BAU Journal - Science and Technology

In this work, a computational study is carried out to investigate the optical response of palladium nano-cylinders. The Finite Element Method (FEM) is employed using the COMSOL MULTIPHYSICS simulation program to calculate the scattering, absorption, and extinction cross-sections. The influence of the size of the cylindrical nanoparticles on their optical properties is discussed. The results are plotted for a broad spectral range of wavelengths from ultra-violet to infra-red of the incident electromagnetic wave on the cylindrical nanoparticles.

Climate Of A Cave Laboratory Representative For Rock Art Caves In The Vézère Area (South-West France), Delphine Lacanette, Léna Bassel, Fabien Salmon, Jean-Christophe Portais, Bruno Bousquet, Rémy Chapoulie, Faten Ammari, Philippe Malaurent, Catherine Ferrier

International Journal of Speleology

Leye Cave (Dordogne, France) is a laboratory cave in the Vézère area, a region that contains some of the most famous rock art caves in the world such as Lascaux, Font-de-Gaume and Combarelles, and is listed as Human World Heritage by UNESCO. Leye Cave was selected because it is representative of painted caves, with respect to parameters such as its geological stage, the presence of water and carbon dioxide, the geological state of its walls, and the size of the cave. These wall states are studied to better understand the conditions of conservation of rock art caves without damaging them. …

Application Of Photoacoustic Imaging For Pneumonia Detection, Caesarany Maqfiroh, Rini Widyaningrum, Ahmad Mujtahid Anas, Mitrayana Mitrayana

Makara Journal of Science

We used photoacoustic imaging (PAI) to visualize and compare acoustic intensity levels in pneumonia-affected and healthy chicken lungs. After histological confirmation of pneumonia, the samples were scanned and subjected to a 532-nm diode laser in a photoacoustic imaging system. The acoustic intensity level of pneumonia-affected tissue was examined and compared with that of healthy lung samples. The optimum laser frequency and duty cycle for imaging the samples were 17 kHz and 30%, respectively. The acoustic intensity levels of pneumonia-affected tissue and healthy lungs were −82.5 ± 1.8 dB and −79.9 ± 1.3 dB, respectively. We found that a simple PAI …

Effect Of Ag2o Nanosheets Thickness On The Performance Of Al/Geo2/Ag2o/Geo2/C Multifunctional Electronic Devices, Atef Fayez Qasrawi Prof. Dr., Hazem Kh Khanfar Prof. Dr.

Journal of the Arab American University مجلة الجامعة العربية الامريكية للبحوث

Herein, stacked layers of germanium oxide comprising silver oxide nanosheets are used to fabricate multifunctional electronic devices. The performance of these devices is enhanced by altering the thickness of Ag2O nanosheets. The effect of

Ag2O nanosheets on the electronic performance of stacked layers of GeO2 is reported. The three stacked layers (GeO2/Ag2O/GeO2; named GAG) which are coated onto Al substrates under a vacuum pressure of 10-5 mbar are subjected to measurements by X-ray diffraction, X-ray photoelectron, X-ray fluorescence, impedance spectroscopy, capacitance –voltage and current-voltage characteristics techniques. The impedance spectroscopy analysis indicates that altering the thickness of the Ag2O layer in …

Anderson Localization Of Electromagnetic Waves In Three Dimensions, Alexey Yamilov, Sergey E. Skipetrov, Tyler W. Hughes, Momchil Minkov, Zongfu Yu, Hui Cao

Physics Faculty Research & Creative Works

Anderson localization is a halt of diffusive wave propagation in disordered systems. Despite extensive studies over the past 40 years, Anderson localization of light in three dimensions has remained elusive, leading to the question of its very existence. Recent advances have enabled finite-difference time-domain calculations to be sped up by orders of magnitude, allowing us to conduct brute-force numerical simulations of light transport in fully disordered three-dimensional systems with unprecedented dimension and refractive index difference. We show numerically three-dimensional localization of vector electromagnetic waves in random aggregates of overlapping metallic spheres, in sharp contrast to the absence of localization for …

Optical Characterisation Of Holographic Diffusers And Bangerter Foils For Treatment Of Amblyopia, Matthew Hellis, Suzanne Martin, Matthew Sheehan, Kevin Murphy

Articles

Amblyopia is a significant issue for children worldwide, and current treatment methods have drawbacks that can hinder treatment effectiveness and/or patient experience. This study proposes a new treatment method using holographic diffusers while also comparing their optical characteristics to a current treatment method (Bangerter foils). Holographic diffusers were developed by optically patterning thin polymer layers on a micron scale. Two compositions of photopolymer (acrylamide and diacetone acrylamide based) are analysed herein. Characterisation shows that holographic diffusers of either composition can achieve a wide range of on-axis intensity reductions, allowing for precise and customisable treatment levels by altering recording exposure time …

Development Of A Particle-In-Cell/Monte Carlo Simulation For Weakly Ionized Plasmas, Xiaochuan (Chloe) Zheng, James Doyle

Macalester Journal of Physics and Astronomy

A plasma is a gaseous system that contains large numbers of electrons and ions that are subject to forces produced by electric and magnetic fields. Weakly ionized plasmas, where the plasma density is much lower than the background gas density, are common in laboratory, atmospheric, and astrophysical situations. Theoretical calculations of plasma properties are challenging due to the complexity of the differential equations used to characterize fundamental physics. Particle-in-cell (PIC) simulations bypass the mathematical difficulties associated with analytic models, at the expense of more complex and time-consuming computer calculations. In this work we developed a one dimensional PIC simulation of …

Tools For Refining The Baryonic Tully-Fisher Relation, Ezra D. Wolf

Macalester Journal of Physics and Astronomy

This paper discusses the development of tools for galactic photometry using wise, and for reduction and analysis of 21cm galaxy spectra. These Python-based tools can then be applied to selected data in order to refine the Baryonic Tully-Fisher Relation. This relation, between baryonic mass and rotational velocity of a galaxy, proves useful for extragalactic research, particularly in calculating redshift-independent distances. While these tools could be further improved, they provide a robust process for calculation of particular galaxy characteristics.

Hydrosphere: Modeling The Planetary Structure Of Ocean Planets And Icy Moons, Karlee R. Taylor

Macalester Journal of Physics and Astronomy

In recent years, “water worlds” have become increasingly of interest to astrobiologists due to their high potential for habitability, as the large amount water on their surfaces is not only necessary for life, but also promises long-term climatic stability. However, also necessary for life is the exchange of chemical compounds between the geosphere and the hydrosphere - something which may be ob- structed by the presence of high pressure ices on these ocean planets and icy moons. In order to explore the habitability of bodies with various surface temperatures, water masses, and core radii, this project develops a model of …

From Experiment To Theory: Investigate The Effect Of Pump Beam Size On Photovoltaic Material Behavior, Dengyu Tu

Macalester Journal of Physics and Astronomy

In orde to investigate the effect of the pump beam size on an ultrafast conductivity measurement experiment, an experiment using Femto XL-500 laser and a simulation using Mathematica were performed. From the experiment data, we found that as the size of the pump beam decreases beyond certain limit, the Drude model can not accurately predict the relationship between conductivity and frequency. In addition, the simulation results corroborate with the experiment result that there is a limit for the size of the pump beam.

Machine Learning Refinements To Metallicity-Dependent Isotopic Abundances, Haoxuan Sun

Macalester Journal of Physics and Astronomy

The project aims to use machine learning algorithms to fit the free parameters of an isotopic scaling model to elemental observations. The processes considered are massive star nucleosynthesis, Type Ia SNe, the s-process, the r-process, and p-isotope production. The analysis on the successful fits seeks to minimize the reduced chi squared between the model and the data. Based upon the successful refinement of the isotopic parameterized scaling model, a table providing the 287 stable isotopic abundances as a function of metallicity, separated into astrophysical processes, is useful for identifying the chemical history of them. The table provides a complete averaged …

Machine Learning Applications For Materials Science: Predicting Properties Of Two-Dimensional Magnetic Materials, Paige Stevenson

Macalester Journal of Physics and Astronomy

We trained successful neural networks to predict the formation energy and magnetic moment of 2-dimensional ferromagnetic materials of similar structure to Cr2Ge2Te6. We collect elemental data on materials with known and unknown properties from easily accessible sources to screen for viable materials for use in future research. Random forest regressors were used to identify the most important predictors of our target qualities, which perform better on predictions of formation energy than magnetic moment. We predict the properties of 1225 materials that are candidates for further research in two-dimensional magnetism and identify several potential sources of error in our models that …

Measuring The Pulse Duration Of A Femtosecond Laser Using Intensity Autocorrelation, Ross N. Relic

Macalester Journal of Physics and Astronomy

In this experiment, an intensity autocorrelator is set up in order to measure the pulse duration of a passively mode-locked Titanium-Sapphire laser with a power of 267mW producing femtosecond pulses. Then this measurement, as well as a measurement of the laser’s spectrum, is used to test the Uncertainty Principle. Intensity autocorrelation is a well-established technique for measuring pulse duration, and is among the more intuitive techniques for this purpose, which is why it was selected for this experiment. The experimental setup was computerized. The delay of one half of the pulse was controlled by a motorized translation stage which was …

Fabricating Perovskite Solar Cells: Fabrication Guide For Limited Lab Capabilities, Erin F. S. Leary

Macalester Journal of Physics and Astronomy

Within the realm of emerging photovoltaics, Perovskite cells are one of the most intriguing technologies. Within a little over a decade, Perovskite solar cells have rivaled the efficiencies of traditional silicon solar cells and strongly outpaced other emerging photovoltaic technologies. This paper aims to show a fabrication guide for creating Perovskite solar cells in a limited lab setting. The fabrication guide created structures with strong physical reliability, but limited electrical reliability. More research is needed to ensure greater reliability and proper electrical function.

Solar Radio Bursts —Deployable Low-Band Ionosphere And Transients Experiment (Dlite) Arrays, Jonathan M. Kazor, Jason Kooi

Macalester Journal of Physics and Astronomy

Solar radio bursts, phenomenon that often accompany CME, solar flares and other solar events, can be detected on earth and used in the prediction of solar weather that affects earth systems in several ways. As part of the NREIP Program supporting the Naval Research Laboratory, Remote Sensing Division, approximately ten interns participated in the analysis of data collected by DLITE and WAVES radio data. Data from DLITE is often used as a complement to data from WAVES due to differences in frequency range and resolution. The analysis helps to correlate the DLITE data with the data collected from other sources. …