First-principles thermoelasticity of bcc iron under pressure

We investigate the elastic and isotropic aggregate properties of ferromagnetic bcc iron as a function of temperature and pressure by computing the Helmholtz free energies for the volume-conserving strained structures using the first-principles linear response linear-muffin-tin-orbital method and the generalized-gradient approximation. We include the electronic excitation contributions to the free energy from the band structures, and phonon contributions from quasi-harmonic lattice dynamics. We make detailed comparisons between our calculated elastic moduli and their temperature and pressure dependences with available experimental and theoretical data.Comment: 5 figures, 2 table

Free-space quantum key distribution

A working free-space quantum key distribution (QKD) system has been developed and tested over a 205-m indoor optical path at Los Alamos National Laboratory under fluorescent lighting conditions. Results show that free-space QKD can provide secure real-time key distribution between parties who have a need to communicate secretly.Comment: 5 pages, 2 figures, 2 tables. To be published in Physical review A on or about 1 April 199

Single top or bottom production associated with a scalar in \gamma p collision as a probe of topcolor-assisted technicolor

In the framework of the topcolor-assisted technicolor (TC2) models, we study the productions of a single top or bottom quark associated with a scalar in \gamma-p collision, which proceed via the subprocesses c\gamma -> t\pi_t^0, c\gamma -> t h_t^0 and c\gamma -> b\pi^+_t mediated by the anomalous top or bottom coupling tc\pi_t^0, tch_t^0 and bc\pi_t^+. These productions, while extremely suppressed in the Standard Model, are found to be significantly enhanced in the large part of the TC2 parameter space, especially the production via c\gamma -> b\pi^+ can have a cross section of 100 fb, which may be accessible and allow for a test of the TC2 models.Comment: 13 pages, 4 figures, comments and references adde

The Application of Mossbauer Spectroscopy to the Study of Corrosion

The Mossbauer spectroscopic methods that have been used for studying corrosion phenomena include transmission, emission and reflection (scatterimg) techniques. Each of these techniques provides unique capabilities for studying a wide range of applied and fundamental corrosion problems. The various Mossbauer spectroscopic techniques are described and compared, and applications of each method to corrosion studies are reviewed

A coudé camera for image-tube work

A new camera designed specifically for image tubes and modern detectors has been installed at the coudé focus of the 2.1-m telescope at Kitt Peak National Observatory. The optical and mechanical design as well as the performance of the camera are discussed

Current-driven ferromagnetic resonance, mechanical torques and rotary motion in magnetic nanostructures

We study theoretically the detection and possible utilization of electric current-induced mechanical torques in ferromagnetic-normal metal heterostructures that are generated by spin-flip scattering or the absorption of transverse spin currents by a ferromagnet. To this end, we analyze the DC voltage signals over a spin valve that is driven by an AC current. In agreement with recent studies, this "rectification", measured as a function of AC frequency and applied magnetic field, contains important information on the magnetostatics and --dynamics. Subsequently, we show that the vibrations excited by spin-transfer to the lattice can be detected as a splitting of the DC voltage resonance. Finally, we propose a concept for a spin-transfer-driven electric nanomotor based on integrating metallic nanowires with carbon nanotubes, in which the current-induced torques generate a rotary motion.Comment: This resubmission corrects typos in Appendix A 26 pages, 7 figure

Facile Protocol for Water-Tolerant “Frustrated Lewis Pair”-Catalyzed Hydrogenation

Despite rapid advances in the field of metal-free, “frustrated Lewis pair” (FLP)-catalyzed hydrogenation, the need for strictly anhydrous reaction conditions has hampered wide-scale uptake of this methodology. Herein, we report that, despite the generally perceived moisture sensitivity of FLPs, 1,4-dioxane solutions of B(C6F5)3 actually show appreciable moisture tolerance and can catalyze hydrogenation of a range of weakly basic substrates without the need for rigorously inert conditions. In particular, reactions can be performed directly in commercially available nonanhydrous solvents without subsequent drying or use of internal desiccants

Water bathing alters threat perception in starlings.

The majority of bird taxa perform water bathing, but little is known about the adaptive value of this behaviour. If bathing is important for feather maintenance then birds that have not bathed should have poorer feather condition, compromised escape ability and therefore increased responsiveness to cues of predation. We conducted two experiments examining the behaviour of captive starlings responding to conspecific alarm calls. Birds that had no access to bathing water showed a decreased willingness to feed and increased their vigilance behaviour following an alarm call. We argue that birds denied access to bathing water interpreted an ambiguous cue of threat as requiring more caution than birds that had access, consistent with higher levels of anxiety. Our results support the provision of bathing water for captive birds as an important welfare measure