Assessing changes in attitudes toward engineering and biomechanics resulting from a high school outreach event.

National Biomechanics Day aims to introduce students to the emerging field of biomechanics and improve their perception of engineering and engineers. This quantitative study examines participants' attitude changes following one such event. By prioritizing increasing excitement and engagement over teaching content, we anticipate that students' opinions of engineering and biomechanics will improve following the event. Pre- and post-test surveys consisting of Likert scale and semantic differential (SD) items assessed changes in three key areas: self-identity as a scientist and engineer, attitudes toward engineering, and attitudes toward biomechanics. Based on unpaired and paired student responses, we found significant gains in all three areas. Students agreed more strongly with statements regarding whether they saw themselves as scientists and engineers, and they had improved attitudes toward engineering in general and biomechanics specifically. The SD scales also reflected improved opinions of both science and biomechanics. These more positive attitudes could eventually lead to more students recruited to study a variety of engineering disciplines, ultimately addressing the ongoing national shortage of qualified engineers.

The presence of a (1 × 1) oxygen overlayer on ZnO(0001) surfaces and at Schottky interfaces.

The atomic surface and interface structures of uncoated and metal-coated epi-polished ZnO(0001) Zn-polar wafers were investigated via surface x-ray diffraction. All uncoated samples showed the presence of a fully occupied (1 × 1) overlayer of oxygen atoms located at the on-top position above the terminating Zn atom, a structure predicted to be unstable by several density functional theory calculations. The same oxygen overlayer was clearly seen at the interface of ZnO with both elemental and oxidized metal Schottky contact layers. No significant atomic relaxations were observed at surfaces and interfaces processed under typical device fabrication conditions.

Hyperquenching for protein cryocrystallography.

When samples having volumes characteristic of protein crystals are plunge cooled in liquid nitrogen or propane, most cooling occurs in the cold gas layer above the liquid. By removing this cold gas layer, cooling rates for small samples and modest plunge velocities are increased to 1.5 × 10(4) K s(-1), with increases of a factor of 100 over current best practice possible with 10 µm samples. Glycerol concentrations required to eliminate water crystallization in protein-free aqueous mixtures drop from ∼28% w/v to as low as 6% w/v. These results will allow many crystals to go from crystallization tray to liquid cryogen to X-ray beam without cryoprotectants. By reducing or eliminating the need for cryoprotectants in growth solutions, they may also simplify the search for crystallization conditions and for optimal screens. The results presented here resolve many puzzles, such as why plunge cooling in liquid nitrogen or propane has, until now, not yielded significantly better diffraction quality than gas-stream cooling.

Quantifying X-ray radiation damage in protein crystals at cryogenic temperatures.

The dependence of radiation damage to protein crystals at cryogenic temperatures upon the X-ray absorption cross-section of the crystal has been examined. Lysozyme crystals containing varying heavy-atom concentrations were irradiated and diffraction patterns were recorded as a function of the total number of incident photons. An experimental protocol and a coefficient of sensitivity to absorbed dose, proportional to the change in relative isotropic B factor, are defined that together yield a sensitive and robust measure of damage. Radiation damage per incident photon increases linearly with the absorption coefficient of the crystal, but damage per absorbed photon is the same for all heavy-atom concentrations. Similar damage per absorbed photon is observed for crystals of three proteins with different molecular sizes and solvent contents.