Charge relaxation in a single-electron Si/SiGe double quantum dot.

We measure the interdot charge relaxation time T1 of a single electron trapped in an accumulation mode Si/SiGe double quantum dot. The energy level structure of the charge qubit is determined using photon assisted tunneling, which reveals the presence of a low-lying excited state. We systematically measure T1 as a function of detuning and interdot tunnel coupling and show that it is tunable over four orders of magnitude, with a maximum of 45 µs for our device configuration.

Coherent three-level mixing in an electronic quantum dot.

We observe magnetic-field-induced level mixing and quantum superposition phenomena between three approaching single-particle states in a quantum dot probed via the ground state of an adjacent quantum dot by single-electron resonant tunneling. The mixing is attributed to anisotropy and anharmonicity in realistic dot confining potentials. The pronounced anticrossing and transfer of strengths (both enhancement and suppression) between resonances can be understood with a simple coherent level mixing model. Superposition can lead to the formation of a dark state by complete cancellation of an otherwise strong resonance, an effect resembling coherent population trapping in a three-level-system of quantum and atom optics.

Triple arthrodesis and subtalar joint arthrodesis. For the treatment of end-stage posterior tibial tendon dysfunction.

The current literature clearly supports the use of subtalar and triple arthrodeses for the treatment of end-stage PTTD. There is debate, however, regarding whether or not an isolated fusion is preferable to the triple arthrodesis. Complete evaluation of the patient's deformity and symptoms is imperative before choosing to perform a rearfoot fusion. If the deformity can be isolated to the STJ, then perhaps a limited fusion is appropriate. With the close interrelationship of the subtalar and midtarsal joints, however, it is the authors' opinion that chronic dysfunction of the posterior tibial tendon infrequently causes isolated STJ pathology. Perhaps earlier intervention in the process of tendon degeneration, before multiple joint adaptations, would warrant an isolated fusion. We anticipate further research into the advantages of STJ and double arthrodeses over the triple arthrodesis. Clearer identification of the patients in whom these limited fusions are warranted is necessary, especially with respect to adult flatfoot secondary to PTTD. Currently, isolated and combined hindfoot fusions continue to be valuable salvage procedures in the treatment of end-stage arthritic deformities.

Triple arthrodesis stabilization: a quantitative analysis of screw versus staple fixation in fresh cadaveric matched-pair specimens.

Qualitative analyses of midfoot stabilization in triple arthrodeses utilizing bone staple versus 4.5-mm cannulated cancellous screw fixation, with and without washers, were performed in fresh cadaveric specimens. Twenty-two trials (11 matched-pair feet) were used for direct comparison. Stiffness, defined as force/displacement, was determined at each talonavicular and calcaneocuboid joint. Ultimate load failure points of each specimen were also calculated. Trial results showed no statistically significant difference in stiffness or ultimate failure between these two forms of midfoot fixation for triple arthrodeses.