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Hope J, RaviChandran N, Vanholsbeeck F, McDaid A. Augmentation of neural activity in peripheral nerve of sheep using 6 kHz subthreshold currents. Physiol Meas 2020; 41:10NT01. [PMID: 33045694 DOI: 10.1088/1361-6579/abc01f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To determine how increased excitability from subthreshold currents would alter neural activity as it propagates through the subthreshold currents. APPROACH Experiments were performed on two Romney cross-breed sheep in vivo, by applying subthreshold currents either at the stimulus site or between the stimulus and recording sites. Neural recordings were obtained from nerve cuff implanted on the peroneal or sciatic nerve branches, while stimulus was applied to either the peroneal nerve or pins placed through the lower hindshank. MAIN RESULTS Showed that subthreshold currents applied to the same site as stimulus increased excitation of underlying nerve fibres (p < 0.005). With stimulus and subthreshold currents applied to different sites on the peroneal nerve, the primary compound action potential (CAP) in the sciatic displayed a temporal shift of -2.5 to -3 µs which agreed with changes observed in the CAP waveform (p > 0.05). SIGNIFICANCE These findings contribute to the understanding of mechanisms in myelinated fibres of subthreshold current neuromodulation therapies.
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Affiliation(s)
- James Hope
- The Department of Mechanical Engineering, The University of Auckland, Auckland 1010, New Zealand. The Dodd Walls Centre for Photonic and Quantum Technologies, Auckland 1010, New Zealand
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Hope J, Aqrawe Z, Lim M, Vanholsbeeck F, McDaid A. Increasing signal amplitude in electrical impedance tomography of neural activity using a parallel resistor inductor capacitor (RLC) circuit. J Neural Eng 2019; 16:066041. [PMID: 31536974 DOI: 10.1088/1741-2552/ab462b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To increase the impedance signal amplitude produced during neural activity using a novel approach of implementing a parallel resistor inductor capacitor (RLC) circuit across the current source used in electrical impedance tomography (EIT) of peripheral nerve. APPROACH The frequency response of the impedance signal was characterized in the range 4-18 kHz, then a frequency range with significant capacitive charge transfer was selected for experiment with the RLC circuit. Design of the RLC circuit was aided by in vitro impedance measurements on nerve and nerve cuff in the range 5 Hz to 50 kHz. MAIN RESULTS The frequency response of the impedance signal across 4-18 kHz showed maximum amplitude at 6-8 kHz, and steady decline in amplitude between 8 and 18 kHz with -6 dB reduction at 14 kHz. The frequency range 17 ± 1 kHz was selected for the RLC experiment. The RLC experiment was performed on four subjects using an RLC circuit designed to produce a resonant frequency of 17 kHz with a bandwidth of 3.6 kHz, and containing a 22 mH inductive element and a 3.45 nF capacitive element with +0.8/- 3.45 nF manual tuning range. With the RLC circuit connected, relative increases in the impedance signal (±3σ noise) of 44% (±15%), 33% (±30%), 37% (±8.6%), and 16% (±19%) were produced. SIGNIFICANCE The increase in impedance signal amplitude at high frequencies, generated by the novel implementation of a parallel RLC circuit across the drive current, improves spatial resolution by increasing the number of parallel drive currents which can be implemented in a frequency division multiplexed (FDM) EIT system, and aids the long term goal of a real-time FDM EIT system by reducing the need for ensemble averaging.
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Affiliation(s)
- J Hope
- The Department of Mechanical Engineering, The University of Auckland, Auckland, New Zealand. Dodd Walls Centre for Photonic and Quantum Technologies, Dunedin, New Zealand
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Hope J, Aristovich K, Chapman CAR, Volschenk A, Vanholsbeeck F, McDaid A. Extracting impedance changes from a frequency multiplexed signal during neural activity in sciatic nerve of rat: preliminary study in vitro. Physiol Meas 2019; 40:034006. [DOI: 10.1088/1361-6579/ab0c24] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Julia R, Ou F, McGoverin C, Vanholsbeeck F, Swift S. Shining a light on antibiotic selection: optimised live/dead fluorescence spectrometry for rapid antimicrobial susceptibility testing. Access Microbiol 2019. [DOI: 10.1099/acmi.ac2019.po0280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Robertson Julia
- 2The Dodd-Walls Centre for Photonic and Quantum Technologies, Dunedin, New Zealand
- 1The University of Auckland, Auckland, New Zealand
| | - Fang Ou
- 2The Dodd-Walls Centre for Photonic and Quantum Technologies, Dunedin, New Zealand
- 1The University of Auckland, Auckland, New Zealand
| | - Cushla McGoverin
- 2The Dodd-Walls Centre for Photonic and Quantum Technologies, Dunedin, New Zealand
- 1The University of Auckland, Auckland, New Zealand
| | - Frederique Vanholsbeeck
- 2The Dodd-Walls Centre for Photonic and Quantum Technologies, Dunedin, New Zealand
- 1The University of Auckland, Auckland, New Zealand
| | - Simon Swift
- 1The University of Auckland, Auckland, New Zealand
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Robertson J, Ou F, McGoverin C, Vanholsbeeck F, Swift S. Rapid selection of an appropriate antibiotic. Infect Dis Health 2018. [DOI: 10.1016/j.idh.2018.09.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Hope J, Vanholsbeeck F, McDaid A. Drive and measurement electrode patterns for electrode impedance tomography (EIT) imaging of neural activity in peripheral nerve. Biomed Phys Eng Express 2018; 4. [DOI: 10.1088/2057-1976/aadff3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 09/10/2018] [Indexed: 11/12/2022]
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Hope J, Vanholsbeeck F, McDaid A. A model of electrical impedance tomography implemented in nerve-cuff for neural-prosthetics control. Physiol Meas 2018; 39:044002. [DOI: 10.1088/1361-6579/aab73a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Ou F, McGoverin C, Swift S, Vanholsbeeck F. Absolute bacterial cell enumeration using flow cytometry. J Appl Microbiol 2017; 123:464-477. [DOI: 10.1111/jam.13508] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 05/18/2017] [Accepted: 06/04/2017] [Indexed: 11/29/2022]
Affiliation(s)
- F. Ou
- Department of Physics; The Dodd-Walls Centre for Photonic and Quantum Technologies; The University of Auckland; Auckland New Zealand
| | - C. McGoverin
- Department of Physics; The Dodd-Walls Centre for Photonic and Quantum Technologies; The University of Auckland; Auckland New Zealand
| | - S. Swift
- School of Medical Sciences; The University of Auckland; Auckland New Zealand
| | - F. Vanholsbeeck
- Department of Physics; The Dodd-Walls Centre for Photonic and Quantum Technologies; The University of Auckland; Auckland New Zealand
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Guo R, McGoverin C, Swift S, Vanholsbeeck F. A rapid and low-cost estimation of bacteria counts in solution using fluorescence spectroscopy. Anal Bioanal Chem 2017; 409:3959-3967. [PMID: 28389919 PMCID: PMC5437196 DOI: 10.1007/s00216-017-0347-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 03/08/2017] [Accepted: 03/28/2017] [Indexed: 11/15/2022]
Abstract
The fluorescence spectrum of bacterially bound acridine orange (AO) was investigated to evaluate its use for the rapid enumeration of bacteria. Escherichia coli ATCC 25922 samples were stained with 2 × 10-2, 2 × 10-3 or 2 × 10-4% w/v AO, followed by 3, 2 or 0 washing cycles, respectively, and fluorescence spectra were recorded using a fibre-based spectroscopic system. Independent component analysis was used to analyse the spectral datasets for each staining method. Bacterial concentration order of magnitude classification models were calculated using independent component weights. The relationship between fluorescence intensity of bound AO and bacterial concentration was not linear. However, the spectral signals collected for AO stain concentration-bacterial concentration pairs were reproducible and unique enough to enable classification of samples. When above 105 CFU ml-1, it was possible to rapidly determine what the order of magnitude of bacterial concentration of a sample was using a combination of two of the sample preparation methods. A relatively inexpensive (around US$10 per test) rapid method (within 25 min of sampling) for enumeration of bacteria by order of magnitude will reduce the time and cost of microbiological tests requiring gross concentration information. Graphical Abstract Fluorescence spectra of bacterially bound acridine orange (AO) were used for the rapid enumeration of bacteria. Order of magnitude bacterial concentration classification models were calculated using independent components analysis of these fluorescence spectra. When above 105 CFU ml-1, it was possible to rapidly determine the order of magnitude of bacterial concentration of a sample using a combination of two sample preparation methods.
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Affiliation(s)
- Rachel Guo
- The Dodd-Walls Centre for Photonic and Quantum Technologies, Department of Physics, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Cushla McGoverin
- The Dodd-Walls Centre for Photonic and Quantum Technologies, Department of Physics, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Simon Swift
- Department of Molecular Medicine and Pathology, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Frederique Vanholsbeeck
- The Dodd-Walls Centre for Photonic and Quantum Technologies, Department of Physics, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand.
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Cheuk ML, Anderson AJ, Han JC, Lippok N, Vanholsbeeck F, Ruddy BP, Loiselle DS, Nielsen PMF, Taberner AJ. Four-Dimensional Imaging of Cardiac Trabeculae Contracting In Vitro Using Gated OCT. IEEE Trans Biomed Eng 2016; 64:218-224. [PMID: 27093310 DOI: 10.1109/tbme.2016.2553154] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Cardiac trabeculae are widely used as experimental muscle preparations for studying heart muscle. However, their geometry (diameter, length, and shape) can vary not only among samples, but also within a sample, leading to inaccuracies in estimating their stress production, volumetric energy output, and/or oxygen consumption. Hence, it is desirable to have a system that can accurately image each trabecula in vitro during an experiment. To this end, we constructed an optical coherence tomography system and implemented a gated imaging procedure to image actively contracting trabeculae and reconstruct their time-varying geometry. By imaging a single cross section while monitoring the developed force, we found that gated stimulation of the muscle was sufficiently repeatable to allow us to reconstruct multiple contractions to form a four-dimensional representation of a single muscle contraction cycle. The complete muscle was imaged at various lengths and the cross-sectional area along the muscle was quantified during the contraction cycle. The variation of cross-sectional area along the length during a contraction tended to increase as the muscle was contracting, and this increase was greater at longer muscle lengths. To our knowledge, this is the first system that is able to measure the geometric change of cardiac trabeculae in vitro during a contraction, allowing cross-sectional stress and other volume-dependent parameters to be estimated with greater accuracy.
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Cheuk ML, Lippok N, Dixon AW, Ruddy BP, Vanholsbeeck F, Nielsen PMF, Taberner AJ. Optical coherence tomography imaging of cardiac trabeculae. Annu Int Conf IEEE Eng Med Biol Soc 2015; 2014:182-5. [PMID: 25569927 DOI: 10.1109/embc.2014.6943559] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
An integrated instrument is being developed to study live cardiac trabeculae, which is capable of stimulating the muscle under controlled conditions while measuring the heat production, force, and sarcomere length distribution. To improve the accuracy of estimation of stress, strain, and volumetric heat production, the geometry of the muscle must be known. A spectral domain optical coherence tomography system (SD-OCT) has been constructed and calibrated to image the trabecula mounted inside the instrument. This system was mounted above the muscle chamber and a series of equally-spaced cross-sectional images were obtained. These were processed using a workflow developed to extract cross-sectional area and volume. The initial results have demonstrated the feasibility of using OCT to capture the overall geometry of cardiac trabecula mounted in the instrument. Further work will be directed to improve the image quality for larger samples and apply meshing algorithms to the acquired data.
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Abstract
Rapid, accurate and sensitive enumeration of bacterial populations in the natural environment is an essential task for many research fields. Widely used standard methods for counting bacteria such as heterotrophic plate count require 1 to 8 days of incubation time for limited accuracy, while more accurate and rapid techniques are often expensive and may require bulky equipment. In the present study, we have developed a computerized optical prototype for bacterial detection. The goal of this research was to estimate the potential of this optical system for Total Viable Bacterial Count in water. For this purpose, we tested water batches with different microbiological content. Bacterial detection was based on fluorescence enhanced by nucleic acid staining. High sensitivity was achieved by a stable diode pumped solid state laser, sensitive CCD spectrometer and in situ excitation and signal collection. The results have shown that the bacterial count from different water origins using our optical setup along with multivariate analysis presents a higher accuracy and a shorter detection time compared to standard methods. For example, in a case where the fluorescence signal is calibrated to the water batch regression line, the relative standard deviation of the optical system enumeration varies between 21 and 36%, while that of the heterotropic plate count counterpart varies between 41 and 59%. In summary, we conclude that the all-fibre optical system may offer the following advantages over conventional methods: near real time examinations, portability, sensitivity, accuracy and ability to detect 10(2) to 10(8) CFU per ml bacterial concentrations.
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Affiliation(s)
- E Bogomolny
- Department of Physics, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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Hsieh ASY, Wong GKL, Murdoch SG, Coen S, Vanholsbeeck F, Leonhardt R, Harvey JD. Combined effect of Raman and parametric gain on single-pump parametric amplifiers. Opt Express 2007; 15:8104-14. [PMID: 19547137 DOI: 10.1364/oe.15.008104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We investigate the combined effect of Raman and parametric gain on single-pump parametric amplifiers. The phasematched parametric gain is shown to depend strongly on the real part of the complex Raman susceptibility. In fused silica fibers this results in a significant reduction in the available parametric gain for signal detunings beyond 10 THz. We are able to experimentally measure this effect for signal detunings ranging from 7 to 22 THz. Finally we discuss the implications of these results for the design of broadband optical parametric amplifiers.
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Abstract
We simulated the intra-acinar contribution to phase III slope (S(acin)) for gases of differing diffusivities (He and SF(6)) by solving equations of diffusive and convective gas transport in multi-branch-point models (MBPM) of the human acinus. We first conducted a sensitivity study of S(acin) to asymmetry and its variability in successive generations. S(acin) increases were greatest when asymmetry and variability of asymmetry were increased at the level of the respiratory bronchioles (generations 17-18) for He and at the level of the alveolar ducts (generations 20-21) for SF(6), corresponding to the location of their respective diffusion fronts. On the basis of this sensitivity study and in keeping with reported acinar morphometry, we built a MBPM that actually reproduced experimental S(acin) values obtained in normal subjects for He, N(2), and SF(6). Ten variants of such a MBPM were constructed to estimate intrinsic S(acin) variability owing to peripheral lung structure. The realistic simulation of S(acin) in the normal lung and the understanding of how asymmetry affects S(acin) for different diffusivity gases make S(acin) a powerful tool to detect structural alterations at different depths in the lung periphery.
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Affiliation(s)
- B Dutrieue
- Biomedical Physics Laboratory, Université Libre de Bruxelles, 1070 Brussels, Belgium.
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