Low-cost reversible tandem lens mesoscope for brain imaging in rodents.

Significance: The development of imaging systems that are cost-efficient and modular is essential for modern neuroscience research.

Aim: In the current study, we designed, developed, and characterized a low-cost reversible tandem lens mesoscope for brain imaging in rodents.

Approach: Using readily available components, we assembled a robust imaging system that is highly efficient and cost-effective.

Rapid detection of viable microbes with 5-cyano-2,3-di-(p-tolyl)tetrazolium chloride and 5(6)-carboxyfluorescein diacetate using a fibre fluorescence spectroscopy system.

Aims: To assess the efficacy of two commercially available viability dyes, 5-cyano-2,3-di-(p-tolyl)tetrazolium chloride (CTC) and 5(6)-carboxyfluorescein diacetate (CFDA), in reporting on viable cell concentration and species using an all-fibre fluorometer.

Methods And Results: Four bacterial species (two Gram-positive and two Gram-negative) commonly associated with food poisoning or food spoilage (Escherichia coli, Salmonella enterica, Staphylococcus aureus, and Bacillus cereus) were stained with CTC or CFDA and the fibre fluorometer was used to collect full fluorescence emission spectra. A good correlation between concentration and fluorescence intensity was found for Gram-negative bacteria between 107 and 108 colony-forming units (CFU) ml-1.

Continuous separation of bacterial cells from large debris using a spiral microfluidic device.

With the global increase in food exchange, rapid identification and enumeration of bacteria has become crucial for protecting consumers from bacterial contamination. Efficient analysis requires the separation of target particles (e.g.

Detection of subtle cartilage and bone tissue degeneration in the equine joint using polarisation-sensitive optical coherence tomography.

Objective: To explore the ability of polarisation-sensitive optical coherence tomography (PS-OCT) to rapidly identify subtle signs of tissue degeneration in the equine joint.

Method: Polarisation-sensitive optical coherence tomography (PS-OCT) images were systematically acquired in four locations along the medial and lateral condyles of the third metacarpal bone in five dissected equine specimens. Intensity and retardation PS-OCT images, and anomalies observed therein, were then compared and validated with high resolution images of the tissue sections obtained using Differential Interference contrast (DIC) optical light microscopy.

Broadband-excitation-based mechanical spectroscopy of highly viscous tissue-mimicking phantoms.

Standard rheometers assess mechanical properties of viscoelastic samples up to 100 Hz, which often hinders the assessment of the local-scale dynamics. We demonstrate that high-frequency analysis can be achieved by inducing broadband waves and monitoring their media-dependent propagation using optical coherence tomography. Here, we present a new broadband wave analysis based on two-dimensional Fourier transformation.

Rapid Detection of Antibiotic Susceptibility Using Live/Dead Spectrometry for Lytic Agents.

Antibiotic resistance is a serious threat to public health. The empiric use of the wrong antibiotic occurs due to urgency in treatment combined with slow, culture-based diagnostic techniques. Inappropriate antibiotic choice can promote the development of antibiotic resistance.

The complex, bidirectional role of extracellular vesicles in infection.

Cells from all domains of life release extracellular vesicles (EVs), packages that carry a cargo of molecules that participate in communication, co-ordination of population behaviours, virulence and immune response mechanisms. Mammalian EVs play an increasingly recognised role to fight infection, yet may also be commandeered to disseminate pathogens and enhance infection. EVs released by bacterial pathogens may deliver toxins to host cells, signalling molecules and new DNA to other bacteria, and act as decoys, protecting infecting bacteria from immune killing.

A novel optical biosensor for in situ and small-scale monitoring of bacterial transport in saturated columns.

In situ monitoring techniques can provide new insight into bacterial transport after inoculating exogenous bacteria into contaminated soils for bioremediation. A real-time and non-destructive optical sensor (the optrode) was employed to monitor in situ transport of two fluorescently labelled bacteria - Green Fluorescent Protein (Gfp)-labelled, hydrophilic Pseudomonas putida and Tomato Fluorescent Protein (td)-labelled, hydrophobic Rhodococcus erythropolis, in a saturated sand column with and without rhamnolipid surfactant. In situ measurements were made at three sampling ports in the column with the optrode in two sets of column experiments.

Impact-induced cartilage damage assessed using polarisation-sensitive optical coherence tomography.

Non-invasive determination of structural changes in articular cartilage immediately after impact and rehydration provides insight into the response and recovery of the soft tissue, as well as provides a potential methodology for clinicians to quantify early degenerative changes. In this study, we use polarisation-sensitive optical coherence tomography (PS-OCT) to examine subtle alterations of the optical properties in healthy and early-stage degenerate articular cartilage immediately after impact loading to identify structurally relevant metrics required for understanding the mechanical factors of osteoarthritic initiation and progression. A custom-designed impact testing rig was used to deliver 0.

Towards real time assessment of intramuscular fat content in meat using optical fiber-based optical coherence tomography.

We consider the use of optical coherence tomography (OCT) imaging to predict the quality of meat. We find that intramuscular fat (IMF) absorbs infrared light about nine times stronger than muscle, which enables us to estimate fat content in intact meat samples. The method is made very efficient by extracting relevant information from the three-dimensional high-resolution images generated by OCT using principal component analysis (PCA).

Fourier domain quantum optical coherence tomography.

Quantum optical coherence tomography (Q-OCT) is the non-classical counterpart of optical coherence tomography (OCT), a high-resolution 3D imaging technique based on white-light interferometry. Because Q-OCT uses a source of frequency-entangled photon pairs, not only is the axial resolution not affected by dispersion mismatch in the interferometer but is also inherently improved by a factor of two. Unfortunately, practical applications of Q-OCT are hindered by image-scrambling artefacts and slow acquisition times.

Augmentation of neural activity in peripheral nerve of sheep using 6 kHz subthreshold currents.

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.

Species Dependence of SYTO 9 Staining of Bacteria.

SYTO 9 is a fluorescent nucleic acid stain that is widely used in microbiology, particularly for fluorescence microscopy and flow cytometry analyzes. Fluorimetry-based analysis, i.e.

Asia-Pacific Optical Sensors Conference: focus issue introduction.

This feature issue of Optics Express contains 17 articles expanding on recent advances in optical sensors presented at the eighth Asia-Pacific Optical Sensors Conference (APOS 2019) held in Auckland, New Zealand, from November 19 to 22, 2019. These articles span sensing for real-time positioning, refractive indices, strain, gas, and temperature using a variety of methods including photoacoustic computed tomography, coherent optical frequency-modulated continuous-wave interferometry, enhanced Bragg gratings, and phase-sensitive optical frequency-domain reflectometry.

Quantum-inspired detection for spectral domain optical coherence tomography.

Intensity levels allowed by safety standards (ICNIRP or ANSI) limit the amount of light that can be used in a clinical setting to image highly scattering or absorptive tissues with optical coherence tomography (OCT). To achieve high-sensitivity imaging at low intensity levels, we adapt a detection scheme-which is used in quantum optics for providing information about spectral correlations of photons-into a standard spectral domain OCT system. This detection scheme is based on the concept of dispersive Fourier transformation, where a fiber introduces a wavelength-dependent time delay measured by a single-pixel detector, usually a high-speed photoreceiver.

Increasing signal amplitude in electrical impedance tomography of neural activity using a parallel resistor inductor capacitor (RLC) circuit.

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.

Bourdieu, networks, and movements: Using the concepts of habitus, field and capital to understand a network analysis of gender differences in undergraduate physics.

Current trends suggest that significant gender disparities exist within Science, Technology, Engineering, and Mathematics (STEM) education at university, with female students being underrepresented in physics, but more equally represented in life sciences (e.g., biology, medicine).

Optical coherence tomography complements confocal microscopy for investigation of multicellular tumour spheroids.

Knowledge of optical properties, such as the refractive index (RI), of biological tissues is important in optical imaging, as they influence the distribution and propagation of light in tissue. To accurately study the response of cancerous cells to drugs, optimised imaging protocols are required. This study uses a simple custom-built spectral domain optical coherence tomography (OCT) system to conduct RI measurements of multicellular spheroids, three-dimensional (3D) in-vitro culture systems, of the cell line HCT116.

Rapid and cost-effective evaluation of bacterial viability using fluorescence spectroscopy.

A rapid and easy method that takes advantage of an inexpensive and portable fibre-based spectroscopic system (optrode) to determine the ratio of live to dead bacteria is proposed. Mixtures of live and dead Escherichia coli with proportions of live:dead cells varying from 0 to 100% were stained using SYTO 9 and propidium iodide (PI) and measured using the optrode. We demonstrated several approaches to obtaining the proportions of live:dead E.

Optimisation of the Protocol for the LIVE/DEAD BacLight Bacterial Viability Kit for Rapid Determination of Bacterial Load.

Rapid antimicrobial susceptibility testing is needed to reduce prescription of inappropriate antibiotics. A rapid alternative to standard culture-based testing is to determine reductions in cell viability using the LIVE/DEAD BacLight Bacterial Viability Kit. We optimised the kit protocol for this application, focusing on simplifying the process by minimising the steps involved and on determining the optimal analytical parameters for fluorescence measurements from the dyes SYTO 9 and propidium iodide (PI).

Bead-Based Flow-Cytometric Cell Counting of Live and Dead Bacteria.

Flow cytometry (FCM) is based on the detection of scattered light and fluorescence to identify cells with characteristics of interest. Many flow cytometers cannot precisely control the flow through its interrogation point and hence the volume and concentration of the sample cannot be immediately obtained. Here we describe the optimization and evaluation of a bead-based method for absolute cell counting applicable to basic flow cytometers without specialized counting features.

Near real-time enumeration of live and dead bacteria using a fibre-based spectroscopic device.

A rapid, cost-effective and easy method that allows on-site determination of the concentration of live and dead bacterial cells using a fibre-based spectroscopic device (the optrode system) is proposed and demonstrated. Identification of live and dead bacteria was achieved by using the commercially available dyes SYTO 9 and propidium iodide, and fluorescence spectra were measured by the optrode. Three spectral processing methods were evaluated for their effectiveness in predicting the original bacterial concentration in the samples: principal components regression (PCR), partial least squares regression (PLSR) and support vector regression (SVR).

Extracting impedance changes from a frequency multiplexed signal during neural activity in sciatic nerve of rat: preliminary study in vitro.

Objective: To establish suitable frequency spacing and demodulation steps to use when extracting impedance changes from frequency division multiplexed (FDM) carrier signals in peripheral nerve.

Approach: Experiments were performed in vitro on cadavers immediately following euthanasia. Neural activity was evoked via stimulation of nerves in the hind paw, while carrier signals were injected, and recordings obtained, with a dual ring nerve cuff implanted on the sciatic nerve.

Extracting morphometric information from rat sciatic nerve using optical coherence tomography.

We apply three optical coherence tomography (OCT) image analysis techniques to extract morphometric information from OCT images obtained on peripheral nerves of rat. The accuracy of each technique is evaluated against histological measurements accurate to +  /    -  1  μm. The three OCT techniques are: (1) average depth-resolved profile (ADRP), (2) autoregressive spectral estimation (AR-SE), and (3) correlation of the derivative spectral estimation (CoD-SE).

Drive and measurement electrode patterns for electrode impedance tomography (EIT) imaging of neural activity in peripheral nerve.

; To establish the performance of several drive and measurement patterns in EIT imaging of neural activity in peripheral nerve, which involves large impedance changes in the nerve's anisotropic length axis.; Twelve drive and measurement electrode patterns are compared using a finite element (FE) four-cylindrical shell model of a peripheral nerve and a 32 channel dual-ring nerve cuff. The central layer of the FE model contains impedance changes representative of neural activity of -0.