Cu(Ir1 - xCrx)2S4: a model system for studying nanoscale phase coexistence at the metal-insulator transition.

Increasingly, nanoscale phase coexistence and hidden broken symmetry states are being found in the vicinity of metal-insulator transitions (MIT), for example, in high temperature superconductors, heavy fermion and colossal magnetoresistive materials, but their importance and possible role in the MIT and related emergent behaviors is not understood. Despite their ubiquity, they are hard to study because they produce weak diffuse signals in most measurements. Here we propose Cu(Ir1 - xCrx)2S4 as a model system, where robust local structural signals lead to key new insights. We demonstrate a hitherto unobserved coexistence of an Ir(4+) charge-localized dimer phase and Cr-ferromagnetism. The resulting phase diagram that takes into account the short range dimer order is highly reminiscent of a generic MIT phase diagram similar to the cuprates. We suggest that the presence of quenched strain from dopant ions acts as an arbiter deciding between the competing ground states.

Nonequilibrium band mapping of unoccupied bulk states below the vacuum level by two-photon photoemission.

We demonstrate angle-resolved, tunable, two-photon photoemission (2PPE) to map a bulk unoccupied band, viz. the Cu sp band 0 to 1 eV below the vacuum level, in the vicinity of the L point. This short-lived bulk band is seen due to the strong optical pump rate, and the observed transition energies and their dispersion with photon energy ℏω, are in excellent agreement with tight-binding band-structure calculations. The variation of the final-state energy with ℏω has a measured slope of ∼1.64 in contrast to values of 1 or 2 observed for 2PPE from two-dimensional states. This unique variation illustrates the significant role of the perpendicular momentum ℏk_{⊥} in 2PPE.

Effects of lidocaine and epinephrine on cutaneous blood flow.

BACKGROUND: Local anaesthetic agents in combination with epinephrine are frequently used in local reconstructive procedures such as skin tumour excision and local flap closure. The purpose of this study was to measure the effect of subdermal injection of lidocaine combined with epinephrine on cutaneous blood flow in the forearm and in the face. METHODS: Thirty injections were performed on the forearm and 40 injections were performed on the face in five healthy volunteers. In both anatomical regions, 0.9% phosphate buffered saline (PBS) was used as a control, and experimental injections included 1% lidocaine either alone or in combination with 1:100,000 epinephrine, and an additional combination of 1% lidocaine with 1:200,000 epinephrine used in the facial experiments. Cutaneous blood flow was measured indirectly using laser Doppler imaging (moorLDI-Mark 2). RESULTS: A statistically significant increase in blood flow was achieved with injection of lidocaine in the forearm compared to saline, whereas a non-statistically significant increase was achieved with saline injection compared to lidocaine in the face. This occurred in the first 5 min in the forearm and 2 min in the face. The addition of 1:100,000 epinephrine to lidocaine resulted in an immediate decrease in cutaneous blood flow which was maximal at 10 min in the forearm and 8 min in the face. This was statistically significant compared to all other injections except for the combination of 1:200,000 epinephrine with lidocaine, injected in the face. CONCLUSIONS: The vascularity of different anatomical areas may account for blood flow differences following injection with saline and lidocaine. Incisions should be delayed for 10 min in the forearm and 8 min in the face following lidocaine+epinephrine injection to allow maximal benefit to take effect. There were no significant differences between 1:100,000 and 1:200,000 epinephrine combined with lidocaine in facial injections his study.