14 research outputs found
Observation of thermal acoustic modes of a droplet coupled to an optomechanical sensor
The bulk acoustic modes of liquid droplets, well understood from a
theoretical perspective, have rarely been observed experimentally. Here, we
report the direct observation of acoustic vibrational modes in a
picoliter-scale droplet, extending up to ~ 40 MHz. This was achieved by
coupling the droplet to an ultra-sensitive optomechanical sensor, which
operates in a thermal-noise limited regime and with a substantial contribution
from acoustic noise in the ambient medium. The droplet vibrational modes
manifest as Fano resonances in the thermal noise spectrum of the sensor. This
is amongst the few reported observations of droplet acoustic modes, and of Fano
interactions in a coupled mechanical oscillator system driven only by thermal
Brownian motion.Comment: 11 pages, 3 figure
Ultrasonic spectroscopy of sessile droplets coupled to optomechanical sensors
We describe a system for interrogating the acoustic properties of
sub-nanoliter liquid samples within an open microfluidics platform. Sessile
droplets were deposited onto integrated optomechanical sensors, which possess
ambient-medium-noise-limited sensitivity and can thus passively sense the
thermally driven acoustic spectrum of the droplets. The droplet acoustic
breathing modes manifest as resonant features in the thermomechanical noise
spectrum of the sensor, in some cases hybridized with the sensor's own
vibrational modes. Excellent agreement is found between experimental
observations and theoretical predictions, over the entire ~ 0 - 40 MHz
operating range of our sensors. With suitable control over droplet size and
morphology, this technique has the potential for precision acoustic sensing of
small-volume biological and chemical samples
All-Optical, Air-Coupled Ultrasonic Detection of Low-Pressure Gas Leaks and Observation of Jet Tones in the MHz Range
We used an ultrasensitive, broadband optomechanical ultrasound sensor to study the acoustic signals produced by pressurized nitrogen escaping from a variety of small syringes. Harmonically related jet tones extending into the MHz region were observed for a certain range of flow (i.e., Reynolds number), which is in qualitative agreement with historical studies on gas jets emitted from pipes and orifices of much larger dimensions. For higher turbulent flow rates, we observed broadband ultrasonic emission in the ~0–5 MHz range, which was likely limited on the upper end due to attenuation in air. These observations are made possible by the broadband, ultrasensitive response (for air-coupled ultrasound) of our optomechanical devices. Aside from being of theoretical interest, our results could have practical implications for the non-contact monitoring and detection of early-stage leaks in pressured fluid systems
Investigation of the Electrical Properties of Microtubule Ensembles under Cell-Like Conditions
Microtubules are hollow cylindrical polymers composed of the highly negatively-charged (~23e), high dipole moment (1750 D) protein α, β- tubulin. While the roles of microtubules in chromosomal segregation, macromolecular transport, and cell migration are relatively well-understood, studies on the electrical properties of microtubules have only recently gained strong interest. Here, we show that while microtubules at physiological concentrations increase solution capacitance, free tubulin has no appreciable effect. Further, we observed a decrease in electrical resistance of solution, with charge transport peaking between 20–60 Hz in the presence of microtubules, consistent with recent findings that microtubules exhibit electric oscillations at such low frequencies. We were able to quantify the capacitance and resistance of the microtubules (MT) network at physiological tubulin concentrations to be 1.27 × 10−5 F and 9.74 × 104 Ω. Our results show that in addition to macromolecular transport, microtubules also act as charge storage devices through counterionic condensation across a broad frequency spectrum. We conclude with a hypothesis of an electrically tunable cytoskeleton where the dielectric properties of tubulin are polymerisation-state dependent
Shagenes A and B, New Tricyclic Sesquiterpenes Produced by an Undescribed Antarctic Octocoral
Oxadiazolylindazole Sodium Channel Modulators are Neuroprotective toward Hippocampal Neurones
Open data from the first and second observing runs of Advanced LIGO and Advanced Virgo
Advanced LIGO and Advanced Virgo are monitoring the sky and collecting gravitational-wave strain data with sufficient sensitivity to detect signals routinely. In this paper we describe the data recorded by these instruments during their first and second observing runs. The main data products are gravitational-wave strain time series sampled at 16384 Hz. The datasets that include this strain measurement can be freely accessed through the Gravitational Wave Open Science Center at http://gw-openscience.org, together with data-quality information essential for the analysis of LIGO and Virgo data, documentation, tutorials, and supporting software