Dual beam swept source optical coherence tomography for microfluidic velocity measurements

Microfluidic flows are an increasing area of interest used for “lab-on-a-chip” bioanalytical techniques, drug discovery, and chemical processing. This requires optical, non-invasive flow-visualization techniques for characterising microfluidic flows. Optical Coherence Tomography (OCT) systems can provide three-dimensional imaging through reasonably-opaque materials with micrometre resolution, coupled to a single optical axis point using optical fibre cables. Developed for imaging the human eye, OCT has been used for the detection of skin cancers and endoscopically in the human body. Industrial applications are growing in popularity including for the monitoring of bond-curing in aerospace, for production-line non-destructive-testing, and for medical device manufacturing and drug encapsulation monitoring. A dual beam Optical Coherence Tomography system has been developed capable of simultaneously imaging microfluidic channel structures, and tracking particles seeded into the flow to measure high velocity flows, using only a single optical access point. This is achieved via a dual optical fibre bundle for light delivery to the sample and a custom high-speed dual channel OCT instrument using an akinetic sweep wavelength laser. The system has 10 μm resolution in air and a sweeping rate of 96 kHz. This OCT system was used to monitor microfluidic flows in 800 μm deep test chips and Poiseuille flows were observed

Air and Sea Transport: Competition Strategies Under Normal and Economic Crisis Environments

Air and sea passenger transport were generally considered as serving different market segments with little competition between them. Recent research has however shown that the existence of a deregulated operating framework can lead to improved competition between the two modes. This article aims first to identify the circumstances under which air and sea transport compete. The second step is to further examine possible reactions to increase their competitive relationship. The Greek Aegean region presents an interesting case study due to its morphology and seasonal demand characteristics. The question on competitive strategies has become even more essential in an environment of economic crisis as that existing currently in the region

Air and Sea Transport: Competition Strategies Under Normal and Economic Crisis Environments

Air and sea passenger transport were generally considered as serving different market segments with little competition between them. Recent research has however shown that the existence of a deregulated operating framework can lead to improved competition between the two modes. This article aims first to identify the circumstances under which air and sea transport compete. The second step is to further examine possible reactions to increase their competitive relationship. The Greek Aegean region presents an interesting case study due to its morphology and seasonal demand characteristics. The question on competitive strategies has become even more essential in an environment of economic crisis as that existing currently in the region

2D spatially-resolved depth-section microfluidic flow velocimetry using dual beam OCT

A dual beam optical coherence tomography (OCT) instrument has been developed for flow measurement that offers advantages over microscope derived imaging techniques. It requires only a single optical access port, allows simultaneous imaging of the microfluidic channel, does not require fluorescent seed particles, and can provide a millimetre-deep depth-section velocity profile (as opposed to horizontal-section). The dual beam instrument performs rapid re-sampling of particle positions, allowing measurement of faster flows. In this paper, we develop the methods and processes necessary to make 2D quantitative measurements of the flow-velocity using dual beam OCT and present exemplar results in a microfluidic chip. A 2D reference measurement of the Poiseuille flow in a microfluidic channel is presented over a spanwise depth range of 700 μm and streamwise length of 1600 μm with a spatial resolution of 10 μm, at velocities up to 50 mm/s. A measurement of a more complex flow field is also demonstrated in a sloped microfluidic section

Metre-per-second microfluidic flow velocimetry with dual beam optical coherence tomography

A novel dual beam Optical Coherence Tomography (OCT) instrument has been developed for high velocity flow measurement, principally in microfluidics applications. The scanned dual beam approach creates a pair of image-frames separated by a small spatiotemporal offset. Metre-per-second flow measurement is achieved by rapid re-imaging by the second beam allowing for particle tracking between each image-frame of the pair. Flow at 1.06 m/s using a single optical access port has been measured, more than two orders of magnitude larger than previously reported OCT systems, at centimetre depth and with millimetre scale depth of field within a microfluidic chip, whilst simultaneously imaging the microfluidic channel structure

Transmission line method for the simulation of Fiber Bragg Gratings

A new method for the analysis and design of fiber Bragg gratings (FBGs) based on the theory of transmission lines has been developed and verified both theoretically and experimentally. The method is an extension of the coupled-mode theory and utilizes the equivalent transmission lines in order to simulate any type of grating, with an easy and direct implementation. The method provides the ability to analyze the optical devices without using full wave approaches, while also facilitating the incorporation of core materials with a complex or non-linear refractive index, non-uniform distributions of the grating&\#x2019;s refractive index, and tilted and phase-shifted gratings. The approach also allows the design of the grating for a given reflection spectra. Numerical results of the method&\#x2019;s application on a randomly varied inscription of the refractive index of a FBG have also been simulated and discussed. Using this method, the characteristics of an erbium-doped (ED)-FBG have been simulated and the predictions verified experimentally

Diminished social motivation in early psychosis is associated with polygenic liability for low vitamin D

Insufficiency of vitamin D levels often occur in individuals with schizophrenia and first-episode psychosis (FEP). However, it is unknown whether this represents a biological predisposition, or it is essentially driven by illness-related alterations in lifestyle habits. Lower vitamin D has also been associated with adverse neurodevelopmental outcomes and predominant negative psychotic symptoms. This study aimed to investigate the contribution of polygenic risk score for circulating 25-hydroxyvitamin D concentration (PRS-vitD) to symptom presentation among individuals with FEP enrolled in the Athens First-Episode Psychosis Research Study (AthensFEP n = 205) and the Psychosis Incident Cohort Outcome Study (PICOS n = 123). The severity of psychopathology was evaluated using the Positive and Negative Syndrome Scale at baseline and follow-up assessments (AthensFEP: 4-weeks follow-up, PICOS: 1-year follow-up). Premorbid intelligence and adjustment domains were also examined as proxy measures of neurodevelopmental deviations. An inverse association between PRS-vitD and severity of negative symptoms, in particular lack of social motivation, was detected in the AthensFEP at baseline (adjusted R2 = 0.04, p < 0.001) and follow-up (adjusted R2 = 0.03, p < 0.01). The above observation was independently validated in PICOS at follow-up (adjusted R2 = 0.06, p < 0.01). No evidence emerged for a relationship between PRS-vitD and premorbid measures of intelligence and adjustment, likely not supporting an impact of lower PRS-vitD on developmental trajectories related to psychotic illness. These findings suggest that polygenic vulnerability to reduced vitamin D impairs motivation and social interaction in individuals with FEP, thereby interventions that encourage outdoor activities and social engagement in this patient group might attenuate enduring negative symptoms

Optics Express: "Metre-per-second microfluidic flow velocimetry with dual beam optical coherence tomography" Rigas Hallam Charrett Ford Tatam

Images and analysis code associated with Optics Express publication: "Metre-per-second microfluidic flow velocimetry with dual beam optical coherence tomography". The code should be run in a jupyter notebook (or other python implementation).EP/L014637/

Uric acid and incident chronic kidney disease in dyslipidemic individuals

<p><b>Background:</b> Elevated uric acid (UA) is a recognized risk factor for chronic kidney disease (CKD). This study aimed to investigate whether this association exists in dyslipidemic patients receiving multifactorial treatment.</p> <p><b>Methods:</b> An observational study conducted in Greece including 1,269 dyslipidemic individuals followed-up in a lipid clinic for ≥3 years. Estimated glomerular filtration rate (eGFR) was calculated by CKD-EPI equation and CKD was defined as ≤60 mL/min/1.73 m². The correlation was assessed between UA levels and the CKD risk after adjusting for potential confounding factors, after defining the following UA quartiles: Q1: < 4, Q2: 4–5, Q3: 5–6, and Q4: > 6 mg/dL.</p> <p><b>Results:</b> After excluding patients with baseline eGFR <60 mL/min/1.73 m², gout and those taking UA-lowering drugs, 1,095 individuals were eligible; of those, 91% and 69% were treated with statins and anti-hypertensive drugs, respectively. During their follow-up (6 years; IQR = 4–10), 11.9% of the subjects developed CKD, whereas the median annual eGFR decline was 0.69 mL/min/1.73 m² (IQR = 0.45–2.33). Multivariate analysis showed that baseline UA levels (HR = 1.26; 95% CI = 1.09–1.45, <i>p</i> = .001), female gender (HR = 1.74; 95% CI = 1.14–2.65, <i>p</i> = .01), age (HR = 1.10; 95% CI = 1.07–1.12, <i>p</i> < .001), diabetes (HR = 1.67; 95% CI = 1.05–2.65, <i>p</i> = .03), cardiovascular disease (HR = 1.62; 95% CI = 1.02–2.58, <i>p</i> = .04), decreased baseline renal function (eGFR <90 mL/min/1.73 m²) (HR = 2.38; 95% CI = 1.14–4.81, <i>p</i> = .02), and low-density lipoprotein cholesterol reduction (HR = 0.995; 95% CI = 0.991–0.998, <i>p</i> = .01) were associated with incident CKD. Additionally, patients with UA ≥6 mg/dL exhibited a higher risk of incident CKD compared with those in the lowest UA quartile (HR = 2.01; 95% CI = 1.11–3.65, <i>p</i> = .02).</p> <p><b>Conclusion:</b> Higher UA levels are correlated with a higher risk of incident CKD in dyslipidemic individuals taking multifactorial treatment.</p