Physics Commons^™

High & Low Resolution Techniques To Solve Protein Structures, Nathan Wright

Science Enabled by Photon Sources: Local Research Interests in Virginia

Protein structure and dynamics form the platform on which almost all biomedical research is currently based, including hot topics like computer-aided drug design and established problems like creating a cure for cancer. Since most proteins are too small to visualize with even an electron microscope, biochemists must use either NMR spectroscopy or x-ray diffraction to determine what the structures look like. In my lab, we combine both techniques to describe fundamentally how normal and mutated proteins behave in muscle cells. We are specifically interested in the structural protein obscurin. This giant muscle protein helps to organize muscle cells, sense muscle …

Optical Techniques To Probe Internal Dynamics Of Soft Materials, Klebert Feitosa

Science Enabled by Photon Sources: Local Research Interests in Virginia

Like many other soft materials, foam displays complex fluid behavior. Under different circumstances it may behave like an elastic solid or a typical fluid depending on driving forces and the interactions between individual bubbles. To understand the inherent complexities of foam flow, an effective method to visualize its internal structure and dynamics is paramount. In this talk, I will introduce two techniques we have used in our lab to probe foam dynamics at the bubble level: optical tomography and confocal microscopy. The results show great promise to unveil the internal mechanisms that lead to the complex fluid behavior of foams.

X-Ray Fluorescence Microscopy: A Tool For Biology, Life Science & Nanomedicine, Stafan Vogt

Science Enabled by Photon Sources: Local Research Interests in Virginia

Trace elements, in particular metals, play a significant role in most known life forms. It is estimated that one-third of all known proteins contain metal cofactors, and the majority of these function as essential metalloenzymes catalyzing biochemical reactions. Trace metals are increasingly recognized as having a critical impact on human health both in their natural occurrence and via therapeutic drugs (e.g., environmental exposure to heavy metals, treatment with cisplatin-based drugs in chemotherapy, ...), and in diseases such as Alzheimer’s. Quantitative study of the distribution of trace elements on the cellular and subcellular level provide important information about functions and pathways …

Harvesting Heat Through Seebeck Spin Tunneling Effect, Costel Constantin

Science Enabled by Photon Sources: Local Research Interests in Virginia

Harvesting the wasted heat released in the atmosphere by electronic devices has become an important issue in microelectronics as devices shrink toward nanoscale dimensions while achieving an increase in operating speed. Spintronic devices that make use of electrons’ spin as an information carrier offer a promising path to create novel efficient devices thus reducing this wasted heat. Thermoelectronics, on the other hand, explores the possibility of converting heat into electrical power. Spin caloritronics is an exciting new research field that takes advantage of both spintronics and thermoelectronics. In this talk, I will present the design of a spin caloritronic device …

The Role Of Photon Sources In Materials Research: Past, Present, & Future, E. Ward Plummer

Science Enabled by Photon Sources: Local Research Interests in Virginia

In this lecture I will trace the development of Light Sources from the early days of parasitic operation to the new billion dollar dedicated facilities. Clearly, the mode of usage has changed, but so has the type of user. How have these facilities balanced the need for beyond the state-of-the art experiments and serving the needs for routine characterization of materials? How can and should these facilities address the needs for the development of a workforce needed for the next generation of machines and science? Have they produced the science and scientists anticipated? Where do we go next, what is …

Pmma Nanocomposites Composed Of Optically Active Doped Inorganic Nanocrystals, Kyle Gipson

Science Enabled by Photon Sources: Local Research Interests in Virginia

As technology advances, more efficient, cost-effective materials and processes are being developed to serve the duties of optical materials within networks. As light transfers data through polymer optical materials, the polymeric matrix absorbs the signal and this phenomenon is known as attenuation. Attenuation occurs via the higher vibrational energies with respect to fluoropolymers that are inherent with hydrocarbon amorphous polymers like polymethyl methacrylate (PMMA).

One solution to realize efficient light emission is to incorporate nanoparticles into the polymer matrix. In the research presented, aqueous solution-polymer precipitation was used to synthesize light harvesting ligand capped luminescent nanoparticles. Tb3+:LaF3 was the chromophore …

Optical Properties& Energy Transfer Dynamics Of Atmospheric Species, Daniel K. Havey

Science Enabled by Photon Sources: Local Research Interests in Virginia

Our research group is interested in how light interacts with small molecules and particulate matter that are important to atmospheric chemistry and climate change. An active project currently being performed in the James Madison University Undergraduate Laser Laboratory involves a detailed mapping of energy transfer rates from excited or metastable states of atomic or molecular species. This talk describes a specific example study with potential relevance to the JLAMP VUV/Soft X-ray User Facility that would investigate relaxation dynamics of metastable Krypton atoms using two-photon photoacoustic spectroscopy at 819 nm and 124 nm. A study like this would provide useful reference …

Surface Modification & Characterization Of Nano-Composite Polymers, Chris Hughes, Brian Augustine

Science Enabled by Photon Sources: Local Research Interests in Virginia

We have studied the modification of surfaces of both PMMA and nano-composite polyhedral oligomeric silsesquioxane (POSS) containing acrylics. These nano-composites can be spun cast from a variety of solvents and the surface chemistry can be modified by exposure to oxygen-containing plasmas. However, we have found that interesting surface structure evolve over the space of several hours after these films are deposited. We have also found that the solvent used for the spin casting of these layers can alter the behaviors of these surfaces. In particular, we found that halogenated solvents can form complexes with the PMMA backbone to increase the …

Research Potential Of The Twisted Photon Beams, Andrei Afanasev

Science Enabled by Photon Sources: Local Research Interests in Virginia

The fact that photon beams can carry large orbital angular momenta was pointed out in a pioneering work by Allen and collaborators [1] and was later demonstrated experimentally. When quantized, such beams can be described in terms of twisted photons [2] that have a peculiar property: their total angular momentum projected on the direction of propagation may range from a few to hundreds of units of h. Accelerator-based light sources may generate such twisted light with high intensities, leading to new applications in several fields of physics. Examples of such applications will be presented in this talk.

[1.] L. Allen …

Development Of A 60,000 Rpm X-Ray Chopper With 25 Nsec Phase Jitter For Crystallography, Eric Maslen

Science Enabled by Photon Sources: Local Research Interests in Virginia

A high speed X-Ray chopper (mechanical shutter) was developed for sub microsecond time-resolved photocrystallography using a synchrotron source. Based on a rim-slotted titanium wheel rotating at a nominal 60,000 r/min, the device has an upper bound timing alignment (aperture passage compared to source pulse edge) jitter of 23 nsec RMS and has been operated consistently at jitters as low as 7 nsec RMS. The spindle was derived from a commercial turbo-molecular pump whose drive was adapted in a fairly simple manner to enable fine control by a secondary wheel phase regulator using conventional, off-the-shelf components. Because the spindle uses magnetic …

Imaging And Rheology Of Complex Granular & Granular-Fluid Flows, Brian Utter

Science Enabled by Photon Sources: Local Research Interests in Virginia

Granular materials are ubiquitous in nature and industry, from avalanches to the mixing of pharmaceuticals, yet the behavior of these “fluids” is poorly understood. While individual particles interact simply through friction and inelastic collisions, the non-linear forces and large number of particles leads to an unpredictable, complex system. History dependence, strong fluctuations and sudden failure are commonly observed, making predictive equations of macroscopic flow difficult or impossible to determine. Our recent work focuses on jamming, avalanching and shear banding in dense granular and granular-fluid flows and, in particular, the effects of external vibration and surface chemistry on flow properties. Ongoing …