6 research outputs found
Optical read out and feedback cooling of a nanostring optomechanical cavity
Optical measurement of the motion of a 940 kHz mechanical resonance of a
silicon nitride nanostring resonator is demonstrated with a read out noise
imprecision reaching 37 dB below that of the resonator's zero-point
fluctuations. Via intensity modulation of the optical probe laser, radiation
pressure feedback is used to cool and damp the mechanical mode from an initial
room temperature occupancy of (K)
down to a phonon occupation of , representing a
mode temperature of mK. The five decades of cooling is enabled
by the system's large single-photon cooperativity and high
quantum efficiency of optical motion detection ().Comment: 13 pages, 13 figure
A microchip optomechanical accelerometer
The monitoring of accelerations is essential for a variety of applications
ranging from inertial navigation to consumer electronics. The basic operation
principle of an accelerometer is to measure the displacement of a flexibly
mounted test mass; sensitive displacement measurement can be realized using
capacitive, piezo-electric, tunnel-current, or optical methods. While optical
readout provides superior displacement resolution and resilience to
electromagnetic interference, current optical accelerometers either do not
allow for chip-scale integration or require bulky test masses. Here we
demonstrate an optomechanical accelerometer that employs ultra-sensitive
all-optical displacement read-out using a planar photonic crystal cavity
monolithically integrated with a nano-tethered test mass of high mechanical
Q-factor. This device architecture allows for full on-chip integration and
achieves a broadband acceleration resolution of 10 \mu g/rt-Hz, a bandwidth
greater than 20 kHz, and a dynamic range of 50 dB with sub-milliwatt optical
power requirements. Moreover, the nano-gram test masses used here allow for
optomechanical back-action in the form of cooling or the optical spring effect,
setting the stage for a new class of motional sensors.Comment: 16 pages, 9 figure
Systemic IL-12 Administration Alters Hepatic Dendritic Cell Stimulation Capabilities
The liver is an immunologically unique organ containing tolerogenic dendritic cells (DC) that maintain an immunosuppressive microenvironment. Although systemic IL-12 administration can improve responses to tumors, the effects of IL-12-based treatments on DC, in particular hepatic DC, remain incompletely understood. In this study, we demonstrate systemic IL-12 administration induces a 2–3 fold increase in conventional, but not plasmacytoid, DC subsets in the liver. Following IL-12 administration, hepatic DC became more phenotypically and functionally mature, resembling the function of splenic DC, but differed as compared to their splenic counterparts in the production of IL-12 following co-stimulation with toll-like receptor (TLR) agonists. Hepatic DCs from IL-12 treated mice acquired enhanced T cell proliferative capabilities similar to levels observed using splenic DCs. Furthermore, IL-12 administration preferentially increased hepatic T cell activation and IFNγ expression in the RENCA mouse model of renal cell carcinoma. Collectively, the data shows systemic IL-12 administration enables hepatic DCs to overcome at least some aspects of the inherently suppressive milieu of the hepatic environment that could have important implications for the design of IL-12-based immunotherapeutic strategies targeting hepatic malignancies and infections