Determination of Diffusion Kinetics of Ketamine in Brain Tissue: Implications for in vitro Mechanistic Studies of Drug Actions.

Ketamine has been in use for over 50 years as a general anesthetic, acting primarily through blockade of N-methyl-D-aspartate receptors in the brain. Recent studies have demonstrated that ketamine also acts as a potent and rapid-acting antidepressant when administered at sub-anesthetic doses. However, the precise mechanism behind this effect remains unclear. We examined the diffusion properties of ketamine in brain tissue to determine their effects in in vitro studies related to the antidepressant action of ketamine. Brain slices from adult mice were exposed to artificial cerebrospinal fluid (aCSF) containing ∼17 µM ketamine HCl for varying amounts of time. The amount of ketamine within each slice was then measured by tandem high-performance liquid chromatography - mass spectrometry to characterize the diffusion of ketamine into brain tissue over time. We successfully modeled the diffusion of ketamine into brain tissue using a mono-exponential function with a time constant of τ = 6.59 min. This curve was then compared to a one-dimensional model of diffusion yielding a diffusion coefficient of approximately 0.12 cm2⋅s-1 for ketamine diffusing into brain tissue. The brain:aCSF partition coefficient for ketamine was determined to be approximately 2.76. Our results suggest that the diffusion properties of ketamine have a significant effect on drug concentrations achieved within brain tissue during in vitro experiments. This information is vital to determine the ketamine concentration necessary for in vitro slice preparation to accurately reflect in vivo doses responsible for its antidepressant actions.

Transport in Floquet-Bloch Bands.

We report Floquet band engineering of long-range transport and direct imaging of Floquet-Bloch bands in an amplitude-modulated optical lattice. In one variety of Floquet-Bloch bands we observe tunable rapid long-range high-fidelity transport of a Bose condensate across thousands of lattice sites. Quenching into an opposite-parity Floquet-hybridized band allows Wannier-Stark localization to be controllably turned on and off using modulation. A central result of this work is the use of transport dynamics to demonstrate direct imaging of a Floquet-Bloch band structure. These results demonstrate that transport in dynamical Floquet-Bloch bands can be mapped to transport in quasistatic effective bands, opening a path to cold atom quantum emulation of ultrafast multiband electronic dynamics.

Observation and Uses of Position-Space Bloch Oscillations in an Ultracold Gas.

We report the observation and characterization of position-space Bloch oscillations using cold atoms in a tilted optical lattice. While momentum-space Bloch oscillations are a common feature of optical lattice experiments, the real-space center-of-mass dynamics are typically unresolvable. In a regime of rapid tunneling and low force, we observe real-space Bloch oscillation amplitudes of hundreds of lattice sites, in both ground and excited bands. We demonstrate two unique capabilities enabled by tracking of Bloch dynamics in position space: measurement of the full position-momentum phase-space evolution during a Bloch cycle, and direct imaging of the lattice band structure. These techniques, along with the ability to exert long-distance coherent control of quantum gases without modulation, may open up new possibilities for quantum control and metrology.

Quantum simulation of ultrafast dynamics using trapped ultracold atoms.

Ultrafast electronic dynamics are typically studied using pulsed lasers. Here we demonstrate a complementary experimental approach: quantum simulation of ultrafast dynamics using trapped ultracold atoms. Counter-intuitively, this technique emulates some of the fastest processes in atomic physics with some of the slowest, leading to a temporal magnification factor of up to 12 orders of magnitude. In these experiments, time-varying forces on neutral atoms in the ground state of a tunable optical trap emulate the electric fields of a pulsed laser acting on bound charged particles. We demonstrate the correspondence with ultrafast science by a sequence of experiments: nonlinear spectroscopy of a many-body bound state, control of the excitation spectrum by potential shaping, observation of sub-cycle unbinding dynamics during strong few-cycle pulses, and direct measurement of carrier-envelope phase dependence of the response to an ultrafast-equivalent pulse. These results establish cold-atom quantum simulation as a complementary tool for studying ultrafast dynamics.

Effusive atomic oven nozzle design using an aligned microcapillary array.

We present a simple and inexpensive design for a multichannel effusive oven nozzle which provides improved atomic beam collimation and thus extended oven lifetimes. Using this design, we demonstrate an atomic lithium source suitable for trapped-atom experiments. At a nozzle temperature of 525 °C, the collimated atomic beam flux directly after the nozzle is 1.2 × 10(14) atoms/s with a peak beam intensity greater than 5.0 × 10(16) atoms/s/sr. This suggests an oven lifetime of several decades of continuous operation.

Recovery heart rate: an indicator of cardiovascular risk among middle school children.

Recovery heart rate (RHR) has been used in adults to evaluate cardiovascular (CV) fitness, but less is known about RHR in children. Data from 1,276 participants in Project Healthy Schools, a school-based intervention in southeast Michigan, were collected. In addition, to demographic characteristics, physiologic factors examined included body mass index (BMI), lipid and glucose levels, blood pressure, and HR. Information on diet, physical activity, and sedentary behavior was collected through self-report. RHR was determined by measurement of HR after a 3-minute step test. Using quartiles of RHR as a marker of fitness, associations with demographic, physiologic, and behavioral factors were explored using χ(2) and Student t tests. Compared with children in the lowest quartile of RHR (i.e., most fit), those in the upper quartile of RHR (i.e., least fit) had greater mean LDL cholesterol (93.0 vs. 86.7 mg/dL; P = 0.02) and lower mean HDL cholesterol (50.9 vs. 55.9 mg/dL; P < 0.001). Children in the upper 95 % of BMI had greater mean RHR compared with those in the normal BMI range (116.6 vs. 100.3 kg/m(2)). Children in the upper quartile of RHR reported fewer days of vigorous to moderate exercise per week compared with children in the lowest quartile of RHR [4.8 vs. 4.1 (P < 0.001) for moderate exercise and 3.6 vs. 3.0 (P = 0.001) for vigorous exercise]. Among middle school children, RHR appears to be associated with physiologic parameters and health behaviors. RHR may be useful for identifying children at increased risk for developing CV risk factors.