Transforming Upper-Division Quantum Mechanics: Learning Goals and Assessment

In order to help students overcome documented difficulties learning quantum mechanics (QM) concepts, we have transformed our upper-division QM I course using principles of learning theory and active engagement. Key components of this process include establishing learning goals and developing a valid, reliable conceptual assessment tool to measure the extent to which students achieve these learning goals. The course learning goals were developed with broad faculty input, and serve as the basis for the design of the course assessment tool. The development of the assessment tool has included significant faculty input and feedback, twenty-one student interviews, a review of PER literature, and administration of the survey to two semesters of QM I students as well as to a cohort of graduate students. Here, we discuss this ongoing development process and present initial findings from our QM class for the past two semesters.

High-speed tuning of visible laser wavelength using a nanoimprinted grating optical tunable filter

We report on a microelectromechanical tunable optical filter incorporating strain-tunable nanoimprinted elastomeric grating with a pitch varied by 18%. This device enables tuning of optical fiber-guided laser wavelength between lambda=473 and 532 nm within 0.5 ms by mechanically modulating the pitch with a silicon microactuator. We also demonstrate the use of the device for obtaining two-color images of livedead-stained cells with the color intensity ratio varied by the actuator voltage applied. The small structure of the device integrated on a silicon chip may be used in portable systems for optical switching and spectroscopy.

A systematically coarse-grained model for DNA, and its predictions for persistence length, stacking, twist, and chirality

We introduce a coarse-grained model of DNA with bases modeled as rigid-bodyellipsoids to capture their anisotropic stereochemistry. Interaction potentialsare all physicochemical and generated from all-atom simulation/parameterizationwith minimal phenomenology. Persistence length, degree of stacking, and twistare studied by molecular dynamics simulation as functions of temperature, saltconcentration, sequence, interaction potential strength, and local positionalong the chain, for both single- and double-stranded DNA where appropriate.The model of DNA shows several phase transitions and crossover regimes inaddition to dehybridization, including unstacking, untwisting, and collapsewhich affect mechanical properties such as rigidity and persistence length. Themodel also exhibits chirality with a stable right-handed and metastableleft-handed helix.

Approximate inclusion of quantum effects in transition path sampling

We propose a method for incorporating nuclear quantum effects in transition path sampling studies of systems that consist of a few degrees of freedom that must be treated quantum mechanically, while the rest are classical-like. We used the normal mode centroid method to describe the quantum subsystem, which is a method that is not CPU intensive but still reasonably accurate. We applied this mixed centroid/classical transition path sampling method to a model system that has nontrivial quantum behavior, and showed that it can capture the correct quantum dynamical features.

ULTRA-COMPACT ACCELERATOR TECHNOLOGIES FOR APPLICATION IN NUCLEAR TECHNIQUES

Beyond the Planck scale

I outline motivations for believing that important quantum gravity effectslie beyond the Planck scale at both higher energies and longer distances andtimes. These motivations arise in part from the study of ultra-high energyscattering, and also from considerations in cosmology. I briefly summarize someinferences about such ultra-planckian physics, and clues we might pursuetowards the principles of a more fundamental theory addressing the knownpuzzles and paradoxes of quantum gravity.

Spontaneous Dimensional Reduction in Short-Distance Quantum Gravity?

Several lines of evidence suggest that quantum gravity at very shortdistances may behave effectively as a two-dimensional theory. I summarize thesehints, and offer an additional argument based on the strong-coupling limit ofthe Wheeler-DeWitt equation. The resulting scenario suggests a novel approachto quantum gravity at the Planck scale.

EXPERIMENTAL STUDIES OF MITIGATION MATERIALS FOR BLAST INDUCED TBI

The objective of this experimental study is to compare the effects of various materials obstructing the flow of a blast wave and the ability of the given material to reduce the damage caused by the blast. Several methods of energy transfer in blast wave flows are known or expected including: material interfaces with impedance mismatches, density changes in a given material, internal shearing, and particle fracture. The theory applied to this research is that the greatest energy transfer within the obstructing material will yield the greatest mitigation effects to the blast. Sample configurations of foam were varied to introduce material interfaces and filler materials with varying densities and impedances (liquids and powders). The samples were loaded according to a small scale blast produced by an explosive driven shock tube housing gram-range charges. The transmitted blast profiles were analyzed for variations in impulse characteristics and frequency components as compared to standard free field profiles. The results showed a rounding effect of the transmitted blast profile for all samples with the effects of the low density fillers surpassing all others tested.United States. Office of Naval Research (N00014-08-1-0261

PLASMONIC ENHANCEMENT OF DIRECT OPTICAL INITIATION OF EXPLOSIVES

MODELING LX-17 DETONATION GROWTH AND DECAY USING THE IGNITION AND GROWTH MODEL