Orientation Sensitive Terahertz Resonances Observed in Protein Crystals

A method is presented for measuring anisotropic THz response for small crystals, Crystal Anisotropy Terahertz Microscopy (CATM). Sucrose CATM measurements find the expected anisotropic phonon resonances. CATM measurements of protein crystals find the expected broadband water absorption is suppressed and strong orientation and hydration dependent resonant features.Comment: 3 page

ANALYSIS OF ARMY CONTRACTING WORKFORCE COMPETENCY ASSESSMENT

The primary purpose of this research is to assess the competencies of the Mission and Installation Contracting Command Field Directorate Office-Fort Sam Houston (MICC FDO-FSH) and Army Contracting Command-Orlando (ACC-ORL) contracting management workforce. Data was gathered through a Contracting Workforce Competency Assessment, based on the newly adopted National Contract Management Association’s (NCMA) Contract Management Standard (CMS). This research answers the four questions based on the assessment results. The research findings indicate buyer task proficiency ratings higher than seller task knowledge ratings. The findings also show that the buyer pre-award process is the highest average rating for both organizations. This analysis will establish a baseline and provide insight for decision makers on where to focus the redesign of training and education and will serve as a benchmark for how the current workforce will perform under the NCMA CMS. Recommendations for maintaining and improving contract management competencies include education, training, and initiatives focused on the NCMA CMS guiding principles for buyer and seller tasks and education, and on training on competencies to improve the organizations' ability to manage disagreements and provide resources for obtaining the Certified Professional Contract Manager (CPCM) certification and for incorporating the CPCM certificate as an equivalent training for those with industry experience.Outstanding ThesisCivilian, Department of the ArmyCivilian, Department of the ArmyCivilian, Department of the ArmyApproved for public release. Distribution is unlimited

Fiber-coupled Antennas for Ultrafast Coherent Terahertz Spectroscopy in Low Temperatures and High Magnetic Fields

For the purposes of measuring the high-frequency complex conductivity of correlated-electron materials at low temperatures and high magnetic fields, a method is introduced for performing coherent time-domain terahertz spectroscopy directly in the cryogenic bore of existing dc and pulsed magnets. Miniature fiber-coupled THz emitters and receivers are constructed and are demonstrated to work down to 1.5 Kelvin and up to 17 Tesla, for eventual use in higher-field magnets. Maintaining the sub-micron alignment between fiber and antenna during thermal cycling, obtaining ultrafast (${<200}$~fs) optical gating pulses at the end of long optical fibers, and designing highly efficient devices that work well with low-power optical gating pulses constitute the major technical challenges of this project. Data on a YBCO superconducting thin film and a high mobility 2D electron gas is shown.Comment: 8 pages, 9 figure

DNA Breathing Dynamics in the Presence of a Terahertz Field

We consider the influence of a terahertz field on the breathing dynamics of double-stranded DNA. We model the spontaneous formation of spatially localized openings of a damped and driven DNA chain, and find that linear instabilities lead to dynamic dimerization, while true local strand separations require a threshold amplitude mechanism. Based on our results we argue that a specific terahertz radiation exposure may significantly affect the natural dynamics of DNA, and thereby influence intricate molecular processes involved in gene expression and DNA replication

Why is THz Sensitive to Protein Functional States? Oxidation State of Cytochrome C

Abstract: We investigate the presence of structural collective motions on a picosecond time scale for the heme protein, cytochrome c, as a function of oxidation and hydration, using terahertz (THz) time-domain spectroscopy and molecular dynamics simulations. Structural collective mode frequencies have been calculated to lie in this frequency range, and the density of states can be considered a measure of flexibility. A dramatic increase in the THz response occurs with oxidation, with the largest increase for lowest hydrations and highest frequencies. For both oxidation states the measured THz response rapidly increases with hydration saturating above ~25% (g H 2 O/g protein), in contrast to the rapid turn-on in dynamics observed at this hydration level for other proteins. Quasi-harmonic collective vibrational modes and dipole-dipole correlation functions are calculated from the molecular dynamics trajectories. The collective mode density of states alone reproduces the measured hydration dependence providing strong evidence of the existence of these collective motions. The large oxidation dependence is reproduced only by the dipole-dipole correlation function, indicating the contrast arises from diffusive motions consistent with structural changes occurring in the vicinity of a buried internal water molecule