ABSTRACT
Atmospheric pressure measurements based on microelectromechanical systems (MEMSs) can extend accessibility to altitude information. A differential pressure sensor using a thin cantilever and an air chamber is a promising sensing element for sub-centimeter resolution. However, its vulnerability to wind and the lack of height estimation algorithms for real-time operation are issues that remain to be solved. We propose a sensor "cap" that cancels the wind effect and noise by utilizing the airflow around a sphere. A set of holes on the spherical cap transmits only the atmospheric pressure to the sensor. In addition, we have developed a height estimation method based on a discrete transfer function model. As a result, both dynamic pressure and noise are suppressed, and height is estimated under a 5 m/s wind, reconstructing the trajectory with an estimation error of 2.8 cm. The developed sensing system enhances height information in outdoor applications such as unmanned aerial vehicles and wave height measurements.
ABSTRACT
Super-resolution vibrational microscopy is promising to increase the degree of multiplexing of nanometer-scale biological imaging because of the narrower spectral linewidth of molecular vibration compared to fluorescence. However, current techniques of super-resolution vibrational microscopy suffer from various limitations including the need for cell fixation, high power loading, or complicated detection schemes. Here, we present reversible saturable optical Raman transitions (RESORT) microscopy, which overcomes these limitations by using photoswitchable stimulated Raman scattering (SRS). We first describe a bright photoswitchable Raman probe (DAE620) and validate its signal activation and depletion characteristics when exposed to low-power (microwatt level) continuous-wave laser light. By harnessing the SRS signal depletion of DAE620 through a donut-shaped beam, we demonstrate super-resolution vibrational imaging of mammalian cells with excellent chemical specificity and spatial resolution beyond the optical diffraction limit. Our results indicate RESORT microscopy to be an effective tool with high potential for multiplexed super-resolution imaging of live cells.
Subject(s)
Microscopy , Vibration , Animals , Microscopy/methods , Spectrum Analysis, Raman/methods , MammalsABSTRACT
Reconstructive spectroscopy in the mid-infrared (MIR) range is an attractive method for miniaturizing MIR spectrometers. Although detectors with a sharp responsivity spectrum and a high dynamic range are required, there remains room for improvement. This article reports on a set of MIR photodetectors that satisfy these requirements with aluminum-covered narrow trench gratings. We experimentally found the optimal grating design, by which the responsivity changed 0.75% of the maximum value per nanometer of wavelength, and the minimum/maximum ratio was 8.7% in the wavelength range of 2.5-3.7 µm. A detector set of this optimal design was capable of accurate and robust reconstruction against measurement errors. This simple design structure based on standard materials will assist in realizing miniature MIR spectrometers.
ABSTRACT
In this study, we propose a microelectromechanical system (MEMS) force sensor for microflow measurements. The sensor is equipped with a flow sensing piezoresistive cantilever and a dummy piezoresistive cantilever, which acts as a temperature reference. Since the dummy cantilever is also in the form of a thin cantilever, the temperature environment of the dummy sensor is almost identical to that of the sensing cantilever. The temperature compensation effect was measured, and the piezoresistive cantilever was combined with a gasket jig to enable the direct implementation of the piezoresistive cantilever in a flow tube. The sensor device stably measured flow rates from 20 µL/s to 400 µL/s in a silicon tube with a 2-mm inner diameter without being disturbed by temperature fluctuations.
ABSTRACT
α-Cyclodextrin and 3,3'-benzophenonedisulfonylimidazole in a unimolecular ratio were stirred at 40 °C for 1 h in the presence of a catalytic amount of Cs2CO3 in DMF, and then treated with sodium hydroxide to give 2A,3A-mannoepoxy-2B-sulfonyl-α-cyclodextrin in 14% isolated yield. The isomer with the reversed saccharide sequence was not detected.
