Buried tendons. An unusual complication of physis fracture.

BACKGROUND: Tendon entrapment as a consequence of forearm fracture is rare. Only a few such tendon incarcerations have been described in the literature. CASE REPORT: An 8-year-old boy presented with inability to extend the middle, ring, and little fingers of his right hand. Six months earlier, he had sustained an open Salter-Harris II distal radius and greenstick ulna fractures treated elsewhere with an external fixator and a Kirshner wire. After clinical evaluation, surgical exploration was decided. During surgery, the deep flexor tendons of these fingers were released from a bone canal proximally to the previous fracture site. Two years postoperatively, the patient presented with growth arrest signs of the palmar aspect of his distal radius. Shortening, epiphysiodesis of the ulna and epiphysiodesis of the radius were performed. CONCLUSION: Three tendons entrapped proximally to a previous fracture site is a unique incident. It indicates the need for a high level of suspicion to recognize and manage these severe complications timely. HIPPOKRATIA 2017, 21(1): 52-54.

Cryogenic setup for trapped ion quantum computing.

We report on the design of a cryogenic setup for trapped ion quantum computing containing a segmented surface electrode trap. The heat shield of our cryostat is designed to attenuate alternating magnetic field noise, resulting in 120 dB reduction of 50 Hz noise along the magnetic field axis. We combine this efficient magnetic shielding with high optical access required for single ion addressing as well as for efficient state detection by placing two lenses each with numerical aperture 0.23 inside the inner heat shield. The cryostat design incorporates vibration isolation to avoid decoherence of optical qubits due to the motion of the cryostat. We measure vibrations of the cryostat of less than ±20 nm over 2 s. In addition to the cryogenic apparatus, we describe the setup required for an operation with 40Ca+ and 88Sr+ ions. The instability of the laser manipulating the optical qubits in 40Ca+ is characterized by yielding a minimum of its Allan deviation of 2.4 ⋅ 10-15 at 0.33 s. To evaluate the performance of the apparatus, we trapped 40Ca+ ions, obtaining a heating rate of 2.14(16) phonons/s and a Gaussian decay of the Ramsey contrast with a 1/e-time of 18.2(8) ms.

Emergence of quasi-long-range order below the Bragg glass transition.

We report small angle neutron scattering rocking-curve measurements of the flux line lattices in the peak effect region in a niobium single crystal. It is found that upon cooling in a magnetic field, the transverse orientational order as well as the longitudinal translational order grow rapidly with decreasing temperature, indicating diminishing population of defects in the ordering vortex matter. Surprisingly, during subsequent warming, longitudinal order increases with increasing temperature, presumably due to annealing of flux-lattice screw dislocations. The observed behavior indicates the gradual emergence of the Bragg glass phase from entangled vortex matter in the peak effect region.

Peak effect in polycrystalline vortex matter.

We report a study of the peak-effect phase diagram of a strongly disordered type-II superconductor V-21 at. %Ti using ac magnetic susceptibility and small-angle neutron scattering (SANS). In this system, the peak effect appears only at fields higher than 3.4 T. The sample is characterized by strong atomic disorder. Vortex states with field-cooled thermal histories show that both deep in the mixed state, as well as close to the peak effect, there exist no long-range orientationally ordered vortex lattices. The SANS scattering radial widths reveal vortex states ordered in the sub-mum scale. We conjecture that the peak effect in this system is a remnant of the Bragg glass disordering transition, but occurs on submicron length scales due to the presence of strong atomic disorder on larger length scales.