Magnetic excitations in infinite-layer nickelates.

The discovery of superconductivity in infinite-layer nickelates brings us tantalizingly close to a material class that mirrors the cuprate superconductors. We measured the magnetic excitations in these nickelates using resonant inelastic x-ray scattering at the Ni L 3-edge. Undoped NdNiO2 possesses a branch of dispersive excitations with a bandwidth of approximately 200 milli-electron volts, which is reminiscent of the spin wave of strongly coupled, antiferromagnetically aligned spins on a square lattice. The substantial damping of these modes indicates the importance of coupling to rare-earth itinerant electrons. Upon doping, the spectral weight and energy decrease slightly, whereas the modes become overdamped. Our results highlight the role of Mottness in infinite-layer nickelates.

Publisher Correction: Electronic structure of the parent compound of superconducting infinite-layer nickelates.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Electronic structure of the parent compound of superconducting infinite-layer nickelates.

The search continues for nickel oxide-based materials with electronic properties similar to cuprate high-temperature superconductors1-10. The recent discovery of superconductivity in the doped infinite-layer nickelate NdNiO2 (refs. 11,12) has strengthened these efforts. Here, we use X-ray spectroscopy and density functional theory to show that the electronic structure of LaNiO2 and NdNiO2, while similar to the cuprates, includes significant distinctions. Unlike cuprates, the rare-earth spacer layer in the infinite-layer nickelate supports a weakly interacting three-dimensional 5d metallic state, which hybridizes with a quasi-two-dimensional, strongly correlated state with [Formula: see text] symmetry in the NiO2 layers. Thus, the infinite-layer nickelate can be regarded as a sibling of the rare-earth intermetallics13-15, which are well known for heavy fermion behaviour, where the NiO2 correlated layers play an analogous role to the 4f states in rare-earth heavy fermion compounds. This Kondo- or Anderson-lattice-like 'oxide-intermetallic' replaces the Mott insulator as the reference state from which superconductivity emerges upon doping.

Motor Effects of Minimal Traumatic Brain Injury in Mice.

Traumatic brain injury (TBI) is considered to be the leading cause of disability and death among young people. Up to 30% of mTBI patients report motor impairments, such as altered coordination and impaired balance and gait. The objective of the present study was to characterize motor performance and motor learning changes, in order to achieve a more thorough understanding of the possible motor consequences of mTBI in humans. Mice were exposed to traumatic brain injury using the weight-drop model and subsequently subjected to a battery of behavioral motor tests. Immunohistochemistry was conducted in order to evaluate neuronal survival and synaptic connectivity. TBI mice showed a different walking pattern on the Erasmus ladder task, without any significant impairment in motor performance and motor learning. In the running wheels, mTBI mice showed reduced activity during the second dark phase and increased activity during the second light phase compared to the control mice. There was no difference in the sum of wheel revolutions throughout the experiment. On the Cat-Walk paradigm, the mice showed a wider frontal base of support post mTBI. The same mice spent a significantly greater percent of time standing on three paws post mTBI compared with controls. mTBI mice also showed a decrease in the number of neurons in the temporal cortex compared with the control group. In summary, mTBI mice suffered from mild motor impairments, minor changes in the circadian clock, and neuronal damage. A more in-depth examination of the mechanisms by which mTBI compensate for motor deficits is necessary.

Fifth metacarpal instability and its effect on hamatometacarpal arthritis patterns-a cadaver study.

Osteoarthritis (OA) of the fifth carpometacarpal joint is a rare diagnosis with most cases occurring post-traumatically. The joint's ligamentous supports have not been described extensively; however we know that the volar and intermetacarpal ligaments acts as the primary stabilizers. The major deforming forces on this joint are the extensor carpi ulnaris (ECU) dorsally and the flexor carpi ulnaris volarly, via the pisimetacarpal ligament. The aim of this study was to determine how the different joint stabilizers contribute to fifth carpometacarpal joint stability and biomechanics. We also sought to describe the OA patterns affecting the fifth carpometacarpal joint. A study was performed on 10 embalmed cadavers. The fifth carpometacarpal joint was evaluated biomechanically through ECU traction and sequential transection of the joint stabilizers. Gross macroscopic evaluation of degenerative changes in the articular surface was conducted and graded on a scale of 0-3 (with 0 representing normal cartilage with no visible lesions). Biomechanical data were available from 18 specimens (10 right; 8 left) and arthritic patterns were available from all 20 specimens (10 right; 10 left). Based on the biomechanical data, the proximal and distal intermetacarpal ligaments were found to be major contributors to stability. The volar stabilizer was a minor contributor to stability and the dorsal stabilizer was a minimal contributor to stability. OA was present in 16/20 specimens (80%) with an average arthritis grade of 1.6 on the right hand and 1.0 on the left hand. The most common site of OA was the dorso-ulnar quadrant.