49 research outputs found
Transient differential reflectivity of ferromagnetic and paramagnetic phases in the bilayered manganite La1.24Sr1.76Mn2O7
Photoinduced effects in a single crystal of bilayered manganites,
La2-2xSr1+2xMn2O7 (x=0.38), were investigated in a wide range of temperatures
by pump-probe measurement at a photon energy of 1.6eV. In a ferromagnetic
metallic state, significant enhancement of positive rise in differential
reflectivity with a slow relaxing time of hundred picoseconds was observed just
below Tc=127K, indicating that the reflectivity change with the slow relaxation
time constant is induced by laser heating. We have also observed an
unconventional fast relaxing component that has a time constant of the order of
ten picoseconds. This fast relaxing component, whose absolute value has an
asymmetric peak at Tc, is presumably due to short-range correlation of
Jahn-Teller distortion.Comment: 13 pages, 4 figures, accepted to Solid State Communication
Non-contact and real-time measurement of heart rate and heart rate variability using microwave reflectometry
In this paper, we present noncontact and noninvasive vital signal detection using a microwave reflectometer. Elimination of noise components due to random movement of human subjects has been the biggest issue for microwave measurement. Appropriate filtering, amplitude control of the reflectometer signal, and cross correlation among multiple reflectometers together with new algorithms have enabled motion artifact elimination, signal peak detection, and data processing for various parameters related to heart rate (HR) and heart rate variability (HRV). We focus here on the real time measurements of instantaneous HR and HRV for practical use. The evaluation by microwave reflectometry is completely noninvasive and feasible even through clothing, which is extremely effective for health maintenance in daily life as well as for preventing sudden death related to, for example, coronary heart disease and ventricular arrhythmia
Atomic collision dynamics in optical lattices
We simulate collisions between two atoms, which move in an optical lattice
under the dipole-dipole interaction. The model describes simultaneously the two
basic dynamical processes, namely the Sisyphus cooling of single atoms, and the
light-induced inelastic collisions between them. We consider the J=1/2 -> J=3/2
laser cooling transition for Cs, Rb and Na. We find that the hotter atoms in a
thermal sample are selectively lost or heated by the collisions, which modifies
the steady state distribution of atomic velocities, reminiscent of the
evaporative cooling process.Comment: 17 pages, 15 figure