Maximum tunneling velocities in symmetric double well potentials

We consider coherent tunneling of one-dimensional model systems in non-cyclic or cyclic symmetric double well potentials. Generic potentials are constructed which allow for analytical estimates of the quantum dynamics in the non-relativistic deep tunneling regime, in terms of the tunneling distance, barrier height and mass (or moment of inertia). For cyclic systems, the results may be scaled to agree well with periodic potentials for which semi-analytical results in terms of Mathieu functions exist. Starting from a wavepacket which is initially localized in one of the potential wells, the subsequent periodic tunneling is associated with tunneling velocities. These velocities (or angular velocities) are evaluated as the ratio of the flux densities versus the probability densities. The maximum velocities are found under the top of the barrier where they scale as the square root of the ratio of barrier height and mass (or moment of inertia), independent of the tunneling distance. They are applied exemplarily to several prototypical molecular models of non-cyclic and cyclic tunneling, including ammonia inversion, Cope rearrangment of semibullvalene, torsions of molecular fragments, and rotational tunneling in strong laser fields. Typical maximum velocities and angular velocities are in the order of a few km/s and from 10 to 100 THz for our non-cyclic and cyclic systems, respectively, much faster than time-averaged velocities. Even for the more extreme case of an electron tunneling through a barrier of height of one Hartree, the velocity is only about one percent of the speed of light. Estimates of the corresponding time scales for passing through {the narrow domain just} below the potential barrier are in the domain from 2 to 40 fs, much shorter than the tunneling times

Communication: Electronic flux induced by crossing the transition state

We present a new effect of chemical reactions, e.g., isomerizations, that occurs when the reactants pass along the transition state, on the way to products. It is based on the well-known fact that at the transition state, the electronic structure of one isomer changes to the other. We discover that this switch of electronic structure causes a strong electronic flux that is well distinguishable from the usual flux of electrons that travel with the nuclei. As a simple but clear example, the effect is demonstrated here for bond length isomerization of Na2 (21Σ+u), with adiabatic crossing the barrier between the inner and outer wells of the double minimum potential that support different “Rydberg” and “ionic” type electronic structures, respectively

Modular stem in total hip arthroplasty for patients with trochanter valgus deformity: surgical technique and case series.

BACKGROUND: Trochanter valgus deformity (TVD) is a rare condition of total hip arthroplasty (THA). Femoral osteotomy could be required in correcting the deformity to implant femoral stem in severe TVD. In this study, we described one unpublished technique of reverse sleeve of S-ROM to get through the complex situation. This study aimed to summarize and evaluate its technical challenges, safety and effectiveness. METHODS: From January 2006 to December 2014, we enrolled patients whose sleeves were implanted towards the great trochanter in THA with TVD. Their demographics, perioperative and postoperative information were recorded. To explore its indication, we measured and analyzed the ratio of greater trochanter/lesser trochanter (G/L ratio) and trochanter valgus angle (TVA). RESULTS: Twelve patients (1 male and 11 female, average age 42.30 ± 10.23) had mean follow-up of 6 years. Among them, only two patients had intraoperative femoral fracture. The survivorship of femoral prosthesis was 100%. The Harris hip score (HHS) increased from preoperative 34.31 ± 14.43 to postoperative 84.12 ± 11.33. All patients\u27 G/L ratio were larger than 1.50. CONCLUSIONS: The reverse sleeve of S-ROM was a reliable method for the patients with severe TVD, which brought satisfying clinical outcomes in mid-term follow-up

Laser powder bed fusion of Fe60(CoCrNiMn)40 medium-entropy alloy with excellent strength-ductility balance

In this study, Fe60(CoCrNiMn)40 medium-entropy alloy (MEA) was fabricated by laser powder bed fusion (LPBF) via mixing of pure Fe and FeCoCrNiMn powders, the processability, microstructure and mechanical properties were systematically investigated, and the mechanism of strengthening and toughening were revealed through combination of experiments and molecular dynamics (MD) simulations. Results show that fraction of BCC phase decreased gradually with increasing volume energy density (VED), and thus heterostructue with varying FCC and BCC phases were produced through regulating the VED. The Fe60(CoCrNiMn)40 MEA (with scanning speeds of 700 and 800 mm/s) showed excellent strength-plasticity balance (e.g. 476 MPa, 612 MPa and 63 %) compared to the equiatomic FeCoCrNiMn HEA, which is ascribed to the synergistic strengthening and toughening effects involving the twinning induced plasticity (TWIP) and the reinforcement caused by the BCC phase (act as reinforced particle) embedded in the FCC matrix