A program to analyse optical coherence tomography images of the ciliary muscle

Purpose: To describe and validate bespoke software designed to extract morphometric data from ciliary muscle Visante Anterior Segment Optical Coherence Tomography (AS-OCT) images. Method: Initially, to ensure the software was capable of appropriately applying tiered refractive index corrections and accurately measuring orthogonal and oblique parameters, 5 sets of custom-made rigid gas-permeable lenses aligned to simulate the sclera and ciliary muscle were imaged by the Visante AS-OCT and were analysed by the software. Human temporal ciliary muscle data from 50 participants extracted via the internal Visante AS-OCT caliper method and the software were compared. The repeatability of the software was also investigated by imaging the temporal ciliary muscle of 10 participants on 2 occasions. Results: The mean difference between the software and the absolute thickness measurements of the rigid gas-permeable lenses were not statistically significantly different from 0 (t = -1.458, p = 0.151). Good correspondence was observed between human ciliary muscle measurements obtained by the software and the internal Visante AS-OCT calipers (maximum thickness t = -0.864, p = 0.392, total length t = 0.860, p = 0.394). The software extracted highly repeatable ciliary muscle measurements (variability ≤6% of mean value). Conclusion: The bespoke software is capable of extracting accurate and repeatable ciliary muscle measurements and is suitable for analysing large data sets

Developments in contact lens measurement:a comparative study of industry standard geometric inspection and optical coherence tomography

Purpose: The aim of this study was to compare a developmental optical coherence tomography (OCT) based contact lens inspection instrument to a widely used geometric inspection instrument (Optimec JCF), to establish the capability of a market focused OCT system. Methods: Measurements of 27 soft spherical contact lenses were made using the Optimec JCF and a new OCT based instrument, the Optimec is830. Twelve of the lenses analysed were specially commissioned from a traditional hydrogel (Contamac GM Advance 49%) and 12 from a silicone hydrogel (Contamac Definitive 65), each set with a range of back optic zone radius (BOZR) and centre thickness (CT) values. Three commercial lenses were also measured; CooperVision MyDay (Stenfilcon A) in −10D, −3D and +6D powers. Two measurements of BOZR, CT and total diameter were made for each lens in temperature controlled saline on both instruments. Results: The results showed that the is830 and JCF measurements were comparable, but that the is830 had a better repeatability coefficient for BOZR (0.065 mm compared to 0.151 mm) and CT (0.008 mm compared to 0.027 mm). Both instruments had similar results for total diameter (0.041 mm compared to 0.044 mm). Conclusions: The OCT based instrument assessed in this study is able to match and improve on the JCF instrument for the measurement of total diameter, back optic zone radius and centre thickness for soft contact lenses in temperature controlled saline

Does rebound tonometry probe misalignment modify intraocular pressure measurements in human eyes?

Purpose. To examine the influence of positional misalignments on intraocular pressure (IOP) measurement with a rebound tonometer. Methods. Using the iCare rebound tonometer, IOP readings were taken from the right eye of 36 healthy subjects at the central corneal apex (CC) and compared to IOP measures using the Goldmann applanation tonometer (GAT). Using a bespoke rig, iCare IOP readings were also taken 2 mm laterally from CC, both nasally and temporally, along with angular deviations of 5 and 10 degrees, both nasally and temporally to the visual axis. Results. Mean IOP ± SD, as measured by GAT, was 14.7±2.5 mmHg versus iCare tonometer readings of 17.4±3.6 mmHg at CC, representing an iCare IOP overestimation of 2.7±2.8 mmHg (P<0.001), which increased at higher average IOPs. IOP at CC using the iCare tonometer was not significantly different to values at lateral displacements. IOP was marginally underestimated with angular deviation of the probe but only reaching significance at 10 degrees nasally. Conclusions. As shown previously, the iCare tonometer overestimates IOP compared to GAT. However, IOP measurement in normal, healthy subjects using the iCare rebound tonometer appears insensitive to misalignments. An IOP underestimation of <1 mmHg with the probe deviated 10 degrees nasally reached statistical but not clinical significance levels. © 2013 Ian G. Beasley et al

Modeling the effect of temperature and relative humidity on exposure to SARS-CoV-2 in a mechanically ventilated room

Computational fluid dynamics models have been developed to predict airborne exposure to the SARS-CoV-2 virus from a coughing person in a mechanically ventilated room. The models were run with three typical indoor air temperatures and relative humidities (RH). Quantile regression was used to indicate whether these have a statistically significant effect on the airborne exposure. Results suggest that evaporation is an important effect. Evaporation leads to respiratory particles, particularly those with initial diameters between 20 and 100 μm, remaining airborne for longer, traveling extended distances and carrying more viruses than expected from their final diameter. In a mechanically ventilated room, with all of the associated complex air movement and turbulence, increasing the RH may result in reduced airborne exposure. However, this effect may be so small that other factors, such as a small change in proximity to the infected person, could rapidly counter the effect. The effect of temperature on the exposure was more complex, with both positive and negative correlations. Therefore, within the range of conditions studied here, there is no clear guidance on how the temperature should be controlled to reduce exposure. The results highlight the importance of ventilation, face coverings and maintaining social distancing for reducing exposure

Modeling and experimental study of dispersion and deposition of respiratory emissions with implications for disease transmission

The ability to model the dispersion of pathogens in exhaled breath is important for characterizing transmission of the SARS-CoV-2 virus and other respiratory pathogens. A Computational Fluid Dynamics (CFD) model of droplet and aerosol emission during exhalations has been developed and for the first time compared directly with experimental data for the dispersion of respiratory and oral bacteria from ten subjects coughing, speaking, and singing in a small unventilated room. The modeled exhalations consist of a warm, humid, gaseous carrier flow and droplets represented by a discrete Lagrangian particle phase which incorporates saliva composition. The simulations and experiments both showed greater deposition of bacteria within 1 m of the subject, and the potential for a substantial number of bacteria to remain airborne, with no clear difference in airborne concentration of small bioaerosols (<10 μm diameter) between 1 and 2 m. The agreement between the model and the experimental data for bacterial deposition directly in front of the subjects was encouraging given the uncertainties in model input parameters and the inherent variability within and between subjects. The ability to predict airborne microbial dispersion and deposition gives confidence in the ability to model the consequences of an exhalation and hence the airborne transmission of respiratory pathogens such as SARS-CoV-2

Substituents modulate biphenyl penetration into lipid membranes

Electrochemical impedance techniques and fluorescence spectroscopic methods have been applied to the study of the interaction of ortho (o)-, meta (m)- and para (p)-Cl-, o-, m- and p-HO-, p-H3CO-, p-H3C-, p-NC- and p-O3− S- substituted biphenyls (BPs) with Hg supported dioleoyl phosphatidylcholine (DOPC) monolayers and DOPC vesicles. Non-planar o-substituted BPs exhibit the weakest interactions whereas planar p-substituted BPs interact to the greatest extent with the DOPC layers. The substituted BP/DOPC monolayer and bilayer interaction depends on the effect of the substituent on the aromatic electron density, which is related to the substituents’ mesomeric Hammetts constants. Substituted BPs with increased ring electron density do not increase the DOPC monolayer thickness on Hg and penetrate the DOPC vesicle membranes to the greatest extent. Substituted BPs with lower ring electron density can cause an increase in the monolayer’s thickness on Hg depending on their location and they remain in the interfacial and superficial layer of the free standing DOPC membranes. Quantum mechanical calculations correlate the binding energy between the substituted BP rings and methyl acetate, as a model for the –CH2-(CO)O-CH2- fragment of a DOPC molecule, with the location of BPs within the DOPC monolayer

Influence of blade row aerodynamics on pneumatic gas turbine instrumentation

Steady state, inter row measurements in multistage axial compressors are relevant to the current design process. The objective in obtaining such data is for evaluation of compressor blading as well as validation for the computer programmes used in compressor design. Multi-hole pressure probes are a reliable and economical method of collecting detailed flowfield data in compressors for these purposes. These probes are calibrated in a uniform flow in a wind tunnel prior to use, to determine their response to a range of flow angles and speeds. When the probe is subsequently used for measurements in the compressor, often the small inter row spacing means that the probe has to be close to the downstream stator passage and upstream rotor. The result is that the probe is no longer situated in the uniform flow in which it was calibrated, in terms of influences from both the upstream rotor and downstream stator. This project presents the investigation of these two effects on steady state pressure probe measurements. The effects of blockage on a probe positioned in front of a stator row in a high speed compressor were studied using CFD. This was also carried out on a large scale probe in a low speed compressor. It was found that the blockage effect caused a reduced mass flow in the downstream stator passage which in turn lead to an altered flow angle and a small reduction in measured total pressure. Experimental in rig calibrations showed that the change in flow angle was due to an angular offset of the pressure distribution about the probe. These calibrations also showed that the wind tunnel calibration was valid in the compressor within a small angular range. The influence of the upstream rotor passing was studied using an unsteady CFD model. Responses of the individual probe ports and the deduced flow angle and total pressure indicated that the steady state blockage effect is present throughout the wake passing. The wake passing was found to be a largely two dimensional effect in that the radial flow component changes in the low speed compressor wakes had little influence. The Total Technology thesis incorporates a management project on the relevant topic of project selection within companies. An existing project selection model was applied to a sample group of projects to determine the applicability of such models. The main findings were that these models can generate useful information for further selection decisions and that the applicability is towards lower budget projects where a structured approach is often not used

SAPHEDRA project : Building a European Platform for evaluation of consequence models

Among risk assessment procedures for hazardous installations, one of the most important parameters to assess is the impact distance. More generally, consequence assessment of accident scenarios is a crucial item in safety assessment. The selection of the more appropriate model for consequence assessment is thus a critical point, in particular when new technologies and emerging risks are considered, since in such frameworks a consolidated modelling approach to consequence assessment is usually absent. To address this issue, the SAPHEDRA project has started in April 2015 and will run until September 2016. It addresses the following research questions: - What are the hazardous phenomena associated with new technologies or new materials? - How suitable are existing models and tools for evaluating the consequences of these hazardous phenomena? - More generally, what confidence can we give to the “traditional tools” used for assessing emerging risks? - Is it possible to define a broadly accepted protocol for the evaluation of these models and tools and can this protocol be applied at EU level? - To reduce uncertainty, is it possible to identify best practices for model application? The project aims to: - Build the framework to allow an objective assessment of the performance of hazard assessment / consequence analysis models and related simulation tools, and their application domains, based on an EU commonly-agreed protocol and a set of test cases derived from well-established experiments, - Build the framework to communicate model assessment results openly and transparently to all stakeholders obtaining a standardized template, 198 - Openly and transparently communicate strategies to select an appropriate model when different models are available, - Provide information on how to get access to relevant models and tools available on a web platform operated in English, accessible to all stakeholders including the public. The session will introduce the project to the participants by providing an overview on the objectives and the work performed. The session will also present two of the major outcomes of the work carried out: a) the review of the modelling approaches and the test campaigns performed; and b) the protocol proposed for the evaluation of the models. Finally, a panel discussion with end-users and stakeholders, in interaction with the audience will enable to collect a feedback on this initiative

Phase phenomena in supported lipid films under varying electric potential

We model cyclic voltammetry experiments on supported lipid films where a non-trivial dependence of the capacitance on the applied voltage is observed. Previously, based on a mean-field treatment of the Flory–Huggins type, under the assumption of strongly screened electrostatic interactions, it has been hypothesized that peaks in the capacitance-vs.-voltage profiles correspond to a sequence of structural or phase transitions within the adsorbed film. To examine this hypothesis, in this study we use both mean-field calculations and Monte Carlo simulations where the electrostatic effects due to the varying electric potential and the presence of salt are accounted for explicitly. Our main focus is on the structure of the film and the desorption–readsorption phenomena. These are found to be driven by a strong competition for the progressively charged-up (hydrophobic) surface between lipid hydrocarbon tails and the electrode counterions (cations). As the surface charge density is raised, the following phenomena within the interface are clearly observed: (i) a gradual displacement of the monolayer from the surface by the counterions, leading to complete monolayer desorption and formation of an electric double layer by the surface, (ii) a transformation of the monolayer into a bilayer upon its desorption, (iii) in the case of zwitterionic (or strongly polar) lipid head groups, the desorption is followed by the bilayer readsorption to the electrodevia interaction with the electric double layer and release of the excess counterions into the bulk solution. We argue then that the voltammetry peaks are associated with a stepwise process of formation of layers of alternating charge: electric double layer – upon film desorption, triple or multi-layer – upon film readsoption