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161 results on '"Paterson, Carl"'

1. Multivariate analysis of Brillouin imaging data by supervised and unsupervised learning

Author

Xiang, YuChen, Seow, Kai Ling C., Paterson, Carl, and Török, Peter

Subjects
Electrical Engineering and Systems Science - Image and Video Processing, Physics - Data Analysis, Statistics and Probability, Physics - Optics
Abstract

Brillouin imaging relies on the reliable extraction of subtle spectral information from hyperspectral datasets. To date, the mainstream practice has been using line fitting of spectral features to retrieve the average peak shift and linewidth parameters. Good results, however, depend heavily on sufficient SNR and may not be applicable in complex samples that consist of spectral mixtures. In this work, we thus propose the use of various multivariate algorithms that can be used to perform supervised or unsupervised analysis of the hyperspectral data, with which we explore advanced image analysis applications, namely unmixing, classification and segmentation in a phantom and live cells. The resulting images are shown to provide more contrast and detail, and obtained on a timescale $10^2$ faster than fitting. The estimated spectral parameters are consistent with those calculated from pure fitting.

Published
2020
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2. Tracking Single Particles using Surface Plasmon Leakage Radiation Speckle

Author

Berk, Joel, Paterson, Carl, and Foreman, Matthew R.

Subjects
Physics - Optics
Abstract

Label free tracking of small bio-particles such as proteins or viruses is of great utility in the study of biological processes, however such experiments are frequently hindered by weak signal strengths and a susceptibility to scattering impurities. To overcome these problems we here propose a novel technique leveraging the enhanced sensitivity of both interferometric detection and the strong field confinement of surface plasmons. Specifically, we show that interference between the field scattered by an analyte particle and a speckle reference field, derived from random scattering of surface plasmons propagating on a rough metal film, enables particle tracking with sub-wavelength accuracy. We present the analytic framework of our technique and verify its robustness to noise through Monte Carlo simulations., Comment: Journal of Lightwave Technology

Published
2020
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3. Detection of Proteoglycan Loss from Articular Cartilage using Brillouin Microscopy, with Applications to Osteoarthritis

Author

Wu, Pei-Jung, Masouleh, Maryam Imani, Dini, Daniele, Paterson, Carl, Torok, Peter, Overby, Darryl R., and Kabakova, Irina V.

Subjects
Physics - Biological Physics, Physics - Optics, Quantitative Biology - Tissues and Organs
Abstract

The degeneration of articular cartilage (AC) occurs in osteoarthritis (OA), which is a leading cause of pain and disability in middle-aged and older people. The early disease related changes in cartilage extra-cellular matrix (ECM) start with depletion of proteoglycan(PG), leading to an increase in tissue hydration and permeability. These early compositional changes are small (<10%) and hence difficult to register with conventional non-invasive imaging technologies (magnetic resonance and ultrasound imaging). Here we apply Brillouin microscopy for detecting changes in the mechanical properties and composition of porcine AC. OA-like degradation is mimicked by enzymatic tissue digestion, and we compare Brillouin microscopy measurements against histological staining of PG depletion over varying digestion times and enzyme concentrations. The non-destructive nature of Brillouin imaging technology opens new avenues for creating minimally invasive arthroscopic devices for OA diagnostics and therapeutic monitoring., Comment: 10 pages, 5 figures

Published
2018

4. The Effect of Ionic Composition on Acoustic Phonon Speeds in Hybrid Perovskites from Brillouin Spectroscopy and Density Functional Theory

Author

Kabakova, Irina V., Azuri, Ido, Chen, Zhuoying, Nayak, Pabitra K., Snaith, Henry J., Kronik, Leeor, Paterson, Carl, Bakulin, Artem A., and Egger, David A.

Subjects
Condensed Matter - Materials Science
Abstract

Hybrid organic-inorganic perovskites (HOIPs) have recently emerged as highly promising solution-processable materials for photovoltaic (PV) and other optoelectronic devices. HOIPs represent a broad family of materials with properties highly tuneable by the ions that make up the perovskite structure as well as their multiple combinations. Interestingly, recent high-efficiency PV devices using HOIPs with substantially improved long-term stability have used combinations of different ionic compositions. The structural dynamics of these systems are unique for semiconducting materials and are currently argued to be central to HOIPs stability and charge-transport properties. Here, we studied the impact of ionic composition on phonon speeds of HOIPs from Brillouin spectroscopy experiments and density functional theory calculations for FAPbBr$_3$, MAPbBr$_3$, MAPbCl$_3$, and the mixed halide MAPbBr$_{1.25}$Cl$_{1.75}$. Our results show that the acoustic phonon speeds can be strongly modified by ionic composition, which we explain by analysing the lead-halide sublattice in detail. The vibrational properties of HOIPs are therefore tuneable by using targeted ionic compositions in the perovskite structure. This tuning can be rationalized with non-trivial effects, for example, considering the influence of the shape and dipole moment of organic cations. This has an important implication to further improvements in the stability and charge-transport properties of these systems.

Published
2018
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5. Brillouin microscopy, what is it really measuring?

Author

Wu, Pei-Jung, Kabakova, Irina, Ruberti, Jeffrey, Sherwood, Joseph M., Dunlop, Iain E., Paterson, Carl, Török, Peter, and Overby, Darryl R.

Subjects
Quantitative Biology - Quantitative Methods, Condensed Matter - Soft Condensed Matter, Physics - Biological Physics, Physics - Optics
Abstract

Brillouin microscopy measures compressibility, but is being increasingly used to assess stiffness of cells and tissues. Using hydrogels with tunable properties, we demonstrate that Brillouin microscopy is insensitive to stiffness of hydrated materials, but depends strongly on water content, consistent with a theoretical model of biphasic compressibility. Empirical correlations between Brillouin measurements and stiffness arise due to their mutual dependence on water content, but correlations vanish once hydration is controlled., Comment: Updated version with expanded discussion, additional data and a mathematical model to relate Brillouin measurements to water content

Published
2017
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17. Double lateral shearing interferometer for the quantitative measurement of tear film topography

Author

Dubra, Alfredo, Paterson, Carl, and Dainty, Christopher

Subjects
Topographical drawing -- Research, Optics -- Research, Interferometry -- Research, Optical instruments -- Research, Algorithms -- Research, Algorithm, Astronomy, Physics
Abstract

A lateral shearing interferometer designed and built for the study of the precorneal tear film topography dynamics and its effect on visual performance is presented. Simple data processing algorithms are discussed and tested on data illustrating different tear topography features: postblink tear undulation, tear breakup, eyelid-produced bumps and ridges, bubbles, and rough precontact lens tear surfaces. OCIS codes: 330.5370, 010.1080, 170.3890, 170.4580, 330.4300, 330.4460.

Published
2005

18. Wave-front reconstruction from shear phase maps by use of the discrete Fourier transform

Author

Dubra, Alfredo, Paterson, Carl, and Dainty, Christopher

Subjects
Optics -- Research, Astronomy, Physics
Abstract

Fast wave-front reconstruction methods are becoming increasingly important, for example, in large astronomical adaptive optics systems and high spatial resolution shear interferometry, where pseudo-inverse matrix methods scale poorly with problem size. Wave-front reconstruction from difference measurements can be achieved by use of fast implementations of the discrete Fourier transform (DFT), obtaining performance comparable with that of the pseudoinverse in terms of the noise propagation coefficient. Existing methods that are based on the use of the DFT give exact results (in the absence of noise) only for the particular case in which the shear is a divisor of the number of samples to be reconstructed. We present two alternate solutions for the more general case when the shear is any integer. In the first solution the dimensions of the problem are enlarged, and in the second the problem is subdivided into a set of smaller problems with shear amplitude equal to one. We also show that the retrieved solutions have minimum norm and calculate the noise propagation coefficient for both methods. The proposed algorithms are implemented and timed against pseudoinverse multiplication. The results show a speed increase by a factor of 50 over the pseudoinverse multiplication for a grid with N = 3 x [10.sup.3] samples. OCIS codes: 010.1080, 010.7350, 220.4840, 000.3860.

Published
2004

21. Analytical and numerical comparison of encoding methods for computer-generated diffractive optical elements

Author

Paterson, Carl and Smith, Robin W.

Subjects
Diffraction -- Research, Image coding -- Research, Astronomy, Physics
Abstract

We present a new, to our knowledge, analysis of the performances of common encoding schemes that are used to design computer-generated diffractive optical elements. A statistical analysis of the fringe width and the positional errors, which are introduced by the encoding process, is used to calculate their effects on the diffraction efficiency and the noise. The analysis is applied to interferogram-type encoding methods that are most suited to analytically designed elements, in particular, the polygon-fringe-tracing and the bitmap, or mosaic, methods. Predictions are verified by use of both numerical simulation and existing empirical results. The analysis is used to compare the relative merits of the different encoding schemes quantitatively in terms of optical performance and computational efficiency criteria.

Published
1999

24. Semi-random multicore fibre design for adaptive multiphoton endoscopy

Author

Kim, Youngchan, Warren, Sean, Favero, Fernando, Stone, James, Clegg, James, Neil, Mark, Paterson, Carl, Knight, Jonathan, French, Paul, Dunsby, Chris, and Engineering & Physical Science Research Council (EPSRC)

Subjects
Endoscopes, Microscopy, Fluorescence, Multiphoton, 0205 Optical Physics, 1005 Communications Technologies, 0906 Electrical And Electronic Engineering, Pollen, Endoscopy, Optics, Equipment Design, Microspheres, Optical Fibers
Abstract

This paper reports the development, modelling and application of a semi-random multicore fibre (MCF) design for adaptive multiphoton endoscopy. The MCF was constructed from 55 sub-units, each comprising 7 single mode cores, in a hexagonally close-packed lattice where each sub-unit had a random angular orientation. The resulting fibre had 385 single mode cores and was double-clad for proximal detection of multiphoton excited fluorescence. The random orientation of each sub-unit in the fibre reduces the symmetry of the positions of the cores in the MCF, reducing the intensity of higher diffracted orders away from the central focal spot formed at the distal tip of the fibre and increasing the maximum size of object that can be imaged. The performance of the MCF was demonstrated by imaging fluorescently labelled beads with both distal and proximal fluorescence detection and pollen grains with distal fluorescence detection. We estimate that the number of independent resolution elements in the final image – measured as the half-maximum area of the two-photon point spread function divided by the area imaged – to be ~3200.

Published
2018

41. Clinical Spectroscopy: general discussion

Author

Goodacre, Royston, primary, Sergo, Valter, additional, Barr, Hugh, additional, Sammon, Christopher, additional, Schultz, Zachary D., additional, Baker, Matthew J., additional, Graham, Duncan, additional, Marques, Maria Paula, additional, Sulé-Suso, Josep, additional, Livermore, James, additional, Faulds, Karen, additional, Sinjab, Faris, additional, Matousek, Pavel, additional, Campbell, Colin J., additional, Dluhy, Richard, additional, Gardner, Peter, additional, Phillips, Christopher, additional, Diem, Max, additional, Wood, Bayden, additional, Apolonskiy, Alexander, additional, Kazarian, Sergei, additional, Fullwood, Leanne, additional, Gough, Kathleen, additional, Petrich, Wolfgang, additional, Lloyd, Gavin, additional, Ibrahim, Ola, additional, Cinque, Gianfelice, additional, Sockalingum, Ganesh Dhruvananda, additional, Stone, Nick, additional, Kendall, Catherine, additional, McAughtrie, Sarah, additional, Perez-Guaita, David, additional, Clark, Louise, additional, Gerwert, Klaus, additional, Bonifacio, Alois, additional, Notingher, Ioan, additional, Lasch, Peter, additional, Bhargava, Rohit, additional, Lepert, Guillaume, additional, Mader, Kerstin, additional, and Paterson, Carl, additional

Published
2016
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45. In vivo multiphoton microscopy using a handheld scanner with lateral and axial motion compensation.

Author

Sherlock, Ben, Warren, Sean C., Alexandrov, Yuriy, Yu, Fei, Stone, James, Knight, Jonathan, Neil, Mark A. A., Paterson, Carl, French, Paul M. W., and Dunsby, Chris

Abstract

This paper reports a handheld multiphoton fluorescence microscope designed for clinical imaging that incorporates axial motion compensation and lateral image stabilization. Spectral domain optical coherence tomography is employed to track the axial position of the skin surface, and lateral motion compensation is realised by imaging the speckle pattern arising from the optical coherence tomography beam illuminating the sample. Our system is able to correct lateral sample velocities of up to approximately 65 μm s−1. Combined with the use of negative curvature microstructured optical fibre to deliver tunable ultrafast radiation to the handheld multiphoton scanner without the need of a dispersion compensation unit, this instrument has potential for a range of clinical applications. The system is used to compensate for both lateral and axial motion of the sample when imaging human skin in vivo. [ABSTRACT FROM AUTHOR]

Published
2018
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