Martin J. Leahy

Advances in poultry litter disposal technology--a review.

The land disposal of waste from the poultry industry and subsequent environmental implications has stimulated interest into cleaner and more useful disposal options. The review presented here details advances in the three main alternative disposal routes for poultry litter, specifically in the last decade. Results of experimental investigations into the optimisation of composting, anaerobic digestion and direct combustion are summarised. These technologies open up increased opportunities to market the energy and nutrients in poultry litter to agricultural and non-agricultural uses. Common problems experienced by the current technologies are the existence and fate of nitrogen as ammonia, pH and temperature levels, moisture content and the economics of alternative disposal methods. Further advancement of these technologies is currently receiving increased interest, both academically and commercially. However, significant financial incentives are required to attract the agricultural industry.

In vivo imaging of the microcirculation of the volar forearm using correlation mapping optical coherence tomography (cmOCT)

Correlation mapping optical coherence tomography (cmOCT) is a recently proposed technique that extends the capabilities of OCT to enable mapping of vasculature networks. The technique is achieved as a processing step on OCT intensity images that does not require any modification to existing OCT hardware. In this paper we apply the cmOCT processing technique to in vivo human imaging of the volar forearm. We illustrate that cmOCT can produce maps of the microcirculation that clearly follow the accepted anatomical structure. We demonstrate that the technique can extract parameters such as capillary density and vessel diameter. These parameters are key clinical markers for the early changes associated with microvascular diseases. Overall the presented results show that cmOCT is a powerful new tool that generates microcirculation maps in a safe non-invasive, non-contact technique which has clear clinical applications.

Comparison of instruments for investigation of microcirculatory blood flow and red blood cell concentration

The use of laser Doppler perfusion imaging (LDPI) and laser speckle perfusion imaging (LSPI) is well known in the noninvasive investigation of microcirculatory blood flow. This work compares the two techniques with the recently developed tissue viability (TiVi) imaging system, which is proposed as a useful tool to quantify red blood cell concentration in microcirculation. Three systems are evaluated with common skin tests such as the use of vasodilating and vasoconstricting drugs (methlynicotinate and clobetasol, respectively) and a reactive hyperaemia maneuver (using a sphygmomanometer). The devices investigated are the laser Doppler line scanner (LDLS), the laser speckle perfusion imager (FLPI)-both from Moor Instruments (Axminster, United Kingdom)-and the TiVi imaging system (WheelsBridge AB, Linkoping, Sweden). Both imaging and point scanning by the devices are used to quantify the provoked reactions. Perfusion images of vasodilatation and vasoconstriction are acquired with both LDLS and FLPI, while TiVi images are acquired with the TiVi imager. Time acquisitions of an averaged region of interest are acquired for temporal studies such as the reactive hyperaemia. In contrast to the change in perfusion over time with pressure, the TiVi imager shows a different response due its measurement of blood concentration rather than perfusion. The responses can be explained by physiological understanding. Although the three devices sample different compartments of tissue, and output essentially different variables, comparisons can be seen between the three systems. The LDLS system proves to be suited to measurement of perfusion in deeper vessels, while FLPI and TiVi showed sensitivity to more superficial nutritional supply. LDLS and FLPI are insensitive to the action of the vasoconstrictor, while TiVi shows the clear boundaries of the reaction. Assessment of the resolution, penetration depth, and acquisition rate of each instrument show complimentary features that should be taken into account when choosing a system for a particular clinical measurement.

Investigating a smartphone imaging unit for photoplethysmography

Current-generation smartphones boast a video unit comprising a camera next to a white light emitting diode and this configuration would be suitable for reflection-mode bio-optical sensing and imaging applications. We demonstrate reflection photoplethysmographic (PPG) imaging using this technology on the index finger of a male volunteer during rest and immediately after performing a short run. The returned signals carry useful PPG signals and were used, for example, to compute change in heart rate. Our results are encouraging, especially in the area of personal and home-based care applications.

Correlation mapping method for generating microcirculation morphology from optical coherence tomography (OCT) intensity images

Standard optical coherence tomography (OCT) in combination with software tools can be harnessed to generate vascular maps in vivo. In this study we have successfully combined a software algorithm based on correlation statistic to reveal microcirculation morphology on OCT intensity images of a mouse brain in vivo captured trans-cranially and through a cranial window. We were able to estimate vessel geometry at bifurcation as well as along vessel segments down-to mean diameters of about 24 μm. Our technique has potential applications in cardiovascular-related parameter measurements such as volumetric flow as well as in assessing vascular density of normal and diseased tissue.

Sub-epidermal imaging using polarized light spectroscopy for assessment of skin microcirculation.

Background/aims: Many clinical conditions that affect the microcirculation of the skin are still diagnosed and followed up by observational methods alone in spite of the fact that non‐invasive, more user‐independent and objective methods are available today. Limited portability, high cost, lack of robustness and non‐specificity of findings are among the factors that have hampered the implementation of these methods in a clinical setting. The aim of this study is to present and evaluate a new, portable and easy‐to‐use imaging technology for investigation of the red blood cell (RBC) concentration in the skin microvasculature based on the method of polarization light spectroscopy using modified standard digital camera technology.

Cellular phone‐based photoplethysmographic imaging

We present study results on visible light reflection photoplethysmographic (PPG) imaging with a mobile cellular phone operated in video imaging mode. PPG signal components around 0.1 Hz attributed to the sympathetic component of the heart rate, 1 Hz as the heart rate and 2 Hz as heart rate high order harmonic were quantified on the index finger of a healthy volunteer. The green channel reported PPG signals throughout the sampled area. The blue and red channel returned plethysmographic information, but the signal strength was highly position specific. Our results obtained with a cellular phone as the data acquisition device are encouraging, especially in the broad context of personal or home-based care and the role of cellular phone technology in medical imaging.

A self-validating digital Coriolis mass-flow meter: an overview

Abstract A new implementation of a Coriolis mass-flow meter transmitter is described. It is based on digital components, and has improved performance compared with the commercial, mostly analogue, transmitter using the same flowtube (transducer). Improvements are found in flowtube control, measurement precision, and performance with two-phase and partially-empty conditions, including batching from empty. The new transmitter is viewed as a second-generation sensor validation (SEVA) demonstrator, in which experience from validating the commercial analogue transmitter has led to a redesign using digital technology. The resulting SEVA transmitter provides improved measurement performance and reduced vulnerability to fault conditions, as well as on-line estimates of measurement quality and fault compensation (Henry and Clarke, Control Engineering practice, 1 (4) (1993) 585–610).

Sensor Validation in Biomedical Applications

Abstract The sensor validation or SEVA project (Henry and Clarke 1991; Henry and Clarke 1993) promotes use of the intelligence in ‘smart’ sensors and the use of standard metrics to efficiently communicate self-diagnostics to the outside world. The standard metrics describe the status of the sensor including on-line uncertainty and a status flag to describe how the current validated measurement value has been derived. The end result is to provide a compact generic description of the quality of a measurement to the controIIer with which decisions as to how to use the measurement can be made. This paper proposes the use of SEVA principles in interpretation of data from biomedical instrumentation in order to aid the decision making process, particularly in critical care. For these pwposes the pulse oximeter and polarographic oxygen tension meter will be used as working examples of typical ‘intelligent sensors’ because they make use of a microprocessor to perform self-diagnostics as well as implementing measurement algorithms.

In-vivo dynamic characterization of microneedle skin penetration using optical coherence tomography.

The use of microneedles as a method of circumventing the barrier properties of the stratum corneum is receiving much attention. Although skin disruption technologies and subsequent transdermal diffusion rates are being extensively studied, no accurate data on depth and closure kinetics of microneedle-induced skin pores are available, primarily due to the cumbersome techniques currently required for skin analysis. We report on the first use of optical coherence tomography technology to image microneedle penetration in real time and in vivo. We show that optical coherence tomography (OCT) can be used to painlessly measure stratum corneum and epidermis thickness, as well as microneedle penetration depth after microneedle insertion. Since OCT is a real-time, in-vivo, nondestructive technique, we also analyze skin healing characteristics and present quantitative data on micropore closure rate. Two locations (the volar forearm and dorsal aspect of the fingertip) have been assessed as suitable candidates for microneedle administration. The results illustrate the applicability of OCT analysis as a tool for microneedle-related skin characterization.