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The Department of Physics hosts a colloquium every month during the fall and spring semesters, typically every fourth Thursday (excluding holidays and final exam days) at 11:00 AM, unless indicated otherwise. Speakers include faculty from the Physics Department as well as faculty and researches from other universities. The subjetcs cover all areas of physics and is expected to attract a broad audience, including Physics Majors and Minors, and to promote research collaboration. The colloquia听are听typically 50 minutes followed by 10 minutes of questions. Because of the COVID-19 pandemic, the colloquia听have听been conducted via Zoom meetings, but this format may change in the future. For more information, please contact Dr. Alcantara-Ortigoza at malcantaraortigoza@tuskegee.edu
Colloquia are held from 11 am to 12 pm, unless otherwise indicated. The meetings are virtual via Zoom. Zoom meeting ID: 听513 619 5883 (No password)
Piezoelectric polymers have been attracting increasing interest in recent years due to their unique properties, such as flexibility, lightweight, and low cost. These properties make them suitable for use in a wide range of advanced sensor applications, including pressure sensors, strain sensors, and energy harvesters. The development of these polymers involves the synthesis and characterization of polymers with piezoelectric properties. One of the most commonly used piezoelectric polymers is polyvinylidene fluoride (PVDF), which has been extensively studied due to its excellent piezoelectric properties and processability. The use of these polymers in sensor applications has shown great potential for a wide range of industries, including healthcare, aerospace, and energy. For example, piezoelectric polymer-based sensors can be used to monitor blood pressure, detect structural defects in aircraft, and harvest energy from vibrations and movements. In conclusion, the development of piezoelectric polymers for advanced sensor applications is an exciting and rapidly evolving field that holds great promise for the future of sensor technology.
Single molecule magnets or nanomagnets provides a perfect ground to understand quantum mechanical behavior such as quantum tunneling in macroscopic systems which is derived from a combination of large spin (S) and easy axis magneto-anisotropy. It contains very rich phenomena spanning from the most fundamental physics to the frontier technologies such as quantum computation. In this talk, I address the Berry phase interference in single molecule magnets, I will focus on proposing how to detect the quantum phase interference in transport phenomena using analytical and numerical approaches. I will also discuss new advances in molecular nanomagnets and future applications in quantum information.
Efficient and controlled mixing of a fuel with air, moving at very high speed, is a challenging physical problem relevant to supersonic and hypersonic combustion. Dr. Solomon's ongoing research focuses on the design and development of nozzle injection systems integrated with ultra-high frequency microactuators. The goal of such an active nozzle injection system is to tailor the instabilities of an injected fluid in favor of enhanced entrainment and mixing in high-speed flow conditions. The actuators, called resonance-enhanced microjets (REM), integrated into the nozzle assemblies, can generate high-frequency compressible streamwise vortices up to 60k kHz. The seminar will cover design details of the active injector assembly, flowfield characterization using the microschlieren imaging technique, nearfield acoustic measurements, and planar laser-induced fluorescence (PLIF) experiments. (Full abstract)
Using Machine Learning to Predict Surface Adsorption
The interaction of molecules on metallic surfaces plays an important role in a wide array of technologies from catalysts that remove harmful gases from the atmosphere to light-harvesting devices and devices to store hydrogen.听 Modeling these types of interactions, between molecules and a metallic substrate, can cost a large amount of computational time, limiting both the amount of systems one can study and the potential to improve device performance.听 To remedy this problem and cut down on computational cost one can employ machine learning techniques.听 In this talk I present the results of utilizing the Hierarchically Interacting Particle Neural Network (HIP-NN), a deep learning neural network, to predict the adsorption of hydrogen on various single crystal surfaces.听 Overall, a trained HIP-NN model predicts both the adsorption heights and energies of hydrogen on these surfaces close to the accuracy of the reference calculations, representing a large step forward in streamlining novel material discovery.听
Sailing on the wings of light
In recent years, solar sails have been successfully built and launched by the Japanese Aerospace Exploration Agency (JAXA) with their IKAROS spacecraft, by NASA with their NanoSail-D spacecraft, and by The Planetary Society with our LightSail 2 spacecraft. A solar sail-propelled spacecraft could reach distant planets and star systems much more quickly than a rocket-propelled spacecraft because of the continual acceleration that solar sailing provides. The technology for interplanetary or interstellar solar sailing is still far from being developed, however. Photonic crystals are advanced materials for solar sailing with high reflectivity, large area over mass ratio, and possibility of thermal control. This presentation is an overview of current efforts building practical solar sails and demonstration of specific type of Anisotropic Photonic Crystal Slab with some promising properties.
Students鈥� understandings of Newton鈥檚 second law
One of the most important topics taught in a first semester introductory physics course is Newton鈥檚 laws. Physics Educations Research (PER) suggests college students bring to the classroom their experiences and own understanding of the physical world. This acquired knowledge often conflicts with the concepts defined in class, thus making the teaching and learning of physics concepts a challenge. On this seminar, I will present results from PER work on which we investigated Newton鈥檚 second laws mental models used in mechanics and electromagnetism (EM). I will also present some ideas that may assist instructors in helping their students to transfer understanding of forces from mechanics to EM topics. Of particular interest is that our research subjects were students in a two-semester calculus-based physics course.听
Differential Response of Type-I interferons - A computational approach to telling the story of interferon signaling pathways
Type I interferons are used effectively in the treatment of Hepatitis C by activating a cascade of interferon-stimulated genes with antiviral properties. The signaling cascade involves the binding of IFN to the two subunits of the IFN receptor, IFNAR1 (R1) and IFNAR2 (R2), to form a ternary complex. The kinases - Jak鈥檚 and Tyk鈥檚 - bound to the cytoplasmic domains of receptor subunits become phosphorylated, which further phosphorylates STAT (p-STAT). Dimers of p-STAT migrate to the nucleus to initiate the transcription of a large number of genes. The subtypes of type I interferons can exhibit differential responses even though they bind to the same receptor subunits and initiate similar signaling pathways. Type I interferons are also known to exhibit a reduced response (refractoriness) to prolonged or multiple doses of IFN. It has been shown that despite binding to the same receptor, the subtype IFN-伪 is more refractory than IFN-尾. The talk focuses on explaining the differential behavior of the subtypes of type I interferon by using computational and analytic tools.听听 听听
Paving the way to clean renewable energy
This talk is about a possible solution to the problem of clean renewable energy. First, I will shortly describe the basic ideas of hydrogen economy, which includes a) hydrogen production from water using solar radiation as a source of energy needed for this process; b) safe storage of hydrogen inside of solid materials; c) conversion of chemical energy of hydrogen into electric energy using hydrogen fuel cell. After short overview of challenges of this endeavor, I will focus on the fuel cell (FC) problems, in particular, on development of new cost-effective and highly active catalysts which are the key elements of FC. Currently platinum-based materials are used as the catalysts in FCs, which make them prohibitively expensive. Rational design of the cost-effective catalysts requires deep understanding of the physics and chemistry behind the processes facilitated by the catalysts: a) release of protons from H2 molecules (hydrogen oxidation) on the FC anodes, b) reaction of the protons with oxygen on the FC cathodes (oxygen reduction reaction). I will illustrate our rational computational design approach to this problem with two examples: a) search for efficient anode catalysts, which not only catalyze hydrogen oxidation, but also remove unwanted carbon monoxide molecules from the anode; b) efficient graphene-based cathode catalyst.听听 听听
Vision and scope of physics听colloquium听and a glimpse of my experience in听 laser spectroscopy
The department physics at 快活视频 has made a cohesive effort to begin a physics colloquium in the department. It is a unique opportunity to bring professionals on a common platform, learn about their scientific interests, and stem a research participation/collaboration. Moreover, it broadens the scope of scientific research that can be helpful in multiple areas of scientific applications.
The rare-earth ions doped glasses are well-known optical materials that have applications in high-power lasers, optical amplifiers, white light-emitting diodes, and solar cells. Glasses of arbitrary composition are easy to tailor when compared to crystals. Therefore, this advantage brings the opportunity to tailor the optical properties via changes in the glass composition. I will present the details of spectroscopic techniques such as UV-Vis-NIR absorption, laser-induced fluorescence, laser-induced excitation spectroscopy, and lifetime measurements to evaluate the optical properties of rare-earth-doped glasses. Besides, I will also present the applications of laser-induced breakdown spectroscopy.