We have measured the magnetic splitting Delta K of a Kondo peak in the differential conductance of a single-electron transistor while tuning the Kondo temperature T K along two different paths in parameter space: varying the dot-lead coupling at a constant dot energy and vice versa. At a high magnetic field B, the changes of DeltaK with TK along the two paths have opposite signs, indicating that Delta K is not a universal function of TK. At low B, we observe a decrease in DeltaK with TK along both paths, in agreement with theoretical predictions. Furthermore, we find Delta K/Delta<1 at low B and Delta K/Delta>1 at high B, where Delta is the Zeeman energy of the bare spin, in the same system.

Low-amplitude electric field (EF) is an important component of woundhealing response and can promote vascular tissue repair; however, the mechanisms of action on endothelium remain unclear. We hypothesized that physiological amplitude EF regulates angiogenic response of microvascular endothelial cells via activation of the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway. A custom set-up allowed non-thermal application of EF of high (7.5 GHz) and low (60 Hz) frequency. Cell responses following up to 24 h of EF exposure, including proliferation and apoptosis, capillary morphogenesis, vascular endothelial growth factor (VEGF) expression and MAPK pathways activation were quantified. A db/db mouse model of diabetic wound healing was used for in vivo validation. High-frequency EF enhanced capillary morphogenesis, VEGF release, MEK-cRaf complex formation, MEK and ERK phosphorylation, whereas no MAPK/JNK and MAPK/p38 pathways activation was observed. The endothelial response to EF did not require VEGF binding to VEGFR2 receptor. EF-induced MEK phosphorylation was reversed in the presence of MEK and Ca 2þ inhibitors, reduced by endothelial nitric oxide synthase inhibition, and did not depend on PI3K pathway activation. The results provide evidence for a novel intracellular mechanism for EF regulation of endothelial angiogenic response via frequency-sensitive MAPK/ERK pathway activation, with important implications for EF-based therapies for vascular tissue regeneration.

We present a study of spin 1/2 Kondo singlets in single electron transistors under a microwave frequency bias excitation. We compare time-averaged conductance G to predicted universal response with respect to microwave frequency, oscillation amplitude and the Kondo temperature and find a non-adiabatic response when the microwave photon energy hf is comparable to the Kondo temperature k B T K . We show that our measurements are qualitatively consistent with the predictions for the radiation-induced decoherence rate of the Kondo spin.

We have characterized the molecular tellurium (Te2) spectrum in the vicinity of the 423nm 1 S0-1 P1 and the 431nm 3 P1-3 P0 transitions in neutral calcium. These transitions are relevant to optical clocks for atomic-beam characterization and cooling (423nm) and enhanced detection (431nm). The use of a Te2 vapor cell as a frequency reference has many advantages over other laser stabilization techniques, and we discuss an application to measuring the instability due to the second-order Doppler shift in a calcium beam clock.