104 research outputs found
Sliding elastic lattice: an explanation of the motion of superconducting vortices
We introduce a system where an elastic lattice of particles is moved slowly
at a constant velocity under the influence of a local external potential,
construct a rigid-body model through simplification processes, and show that
the two systems produce similar results. Then, we apply our model to a
superconducting vortex system and produce path patterns similar to the ones
reported in [Lee et al., Phys. Rev. B 84, 060515 (2011)] suggesting that the
reasoning of the simplification processes in this paper can be a possible
explanation of the experimentally observed phenomenon.Comment: 5 pages, 3 figures, Submitted to Physical Review Letters; Reference
[17] Lee et al., Phys. Rev. B Accepted changed to Lee et al., Phys. Rev. B
84, 060515 (2011
A background correction method to compensate illumination variation in hyperspectral imaging.
Hyperspectral imaging (HSI) can measure both spatial (morphological) and spectral (biochemical) information from biological tissues. While HSI appears promising for biomedical applications, interpretation of hyperspectral images can be challenging when data is acquired in complex biological environments. Variations in surface topology or optical power distribution at the sample, encountered for example during endoscopy, can lead to errors in post-processing of the HSI data, compromising disease diagnostic capabilities. Here, we propose a background correction method to compensate for such variations, which estimates the optical properties of illumination at the target based on the normalised spectral profile of the light source and the measured HSI intensity values at a fixed wavelength where the absorption characteristics of the sample are relatively low (in this case, 800 nm). We demonstrate the feasibility of the proposed method by imaging blood samples, tissue-mimicking phantoms, and ex vivo chicken tissue. Moreover, using synthetic HSI data composed from experimentally measured spectra, we show the proposed method would improve statistical analysis of HSI data. The proposed method could help the implementation of HSI techniques in practical clinical applications, where controlling the illumination pattern and power is difficult
Active illumination using a digital micromirror device for quantitative phase imaging
We present a powerful and cost-effective method for active illumination using
a digital micromirror device (DMD) for quantitative phase imaging techniques.
Displaying binary illumination patterns on a DMD with appropriate spatial
filtering, plane waves with various illumination angles are generated and
impinged onto a sample. Complex optical fields of the sample obtained with
various incident angles are then measured via Mach-Zehnder interferometry, from
which a high-resolution two-dimensional synthetic aperture phase image and a
three-dimensional refractive index tomogram of the sample are reconstructed. We
demonstrate the fast and stable illumination control capability of the proposed
method by imaging colloidal spheres and biological cells, including a human red
blood cell and a HeLa cell
Extended Axion Dark Matter Search Using the CAPP18T Haloscope
We report an extended search for the axion dark matter using the CAPP18T
haloscope. The CAPP18T experiment adopts innovative technologies of a
high-temperature superconducting magnet and a Josephson parametric converter.
The CAPP18T detector was reconstructed after an unexpected incident of the
high-temperature superconducting magnet quenching. The system reconstruction
includes rebuilding the magnet, improving the impedance matching in the
microwave chain, and mechanically readjusting the tuning rod to the cavity for
improved thermal contact. The total system noise temperature is 0.6\,K.
The coupling between the cavity and the strong antenna is maintained at to enhance the axion search scanning speed. The scan frequency range
is from 4.8077 to 4.8181 GHz. No significant indication of the axion dark
matter signature is observed. The results set the best upper bound of the
axion-photon-photon coupling () in the mass ranges of 19.883
to 19.926\,eV at 0.7 or
1.9 with 90\,\% confidence
level. The results demonstrate that a reliable search of the high-mass dark
matter axions can be achieved beyond the benchmark models using the technology
adopted in CAPP18T.Comment: 7 pages and 4 figure
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