De universitaire onderzoeker

Rede Wageninge

Enhanced photoacoustic spectroscopy sensitivity through intra-cavity OPO excitation

We report an optical molecular gas sensor exhibiting high levels of selectivity and sensitivity. The outstanding sensitivity demonstrated by our technology is rooted in a novel combination of photoacoustic spectroscopy (PAS) operated within the cavity of a continuous-wave, intra-cavity Optical Parametric Oscillator (OPO). We exploit the very high circulating field present within the resonant down-converted cavity as the excitation source of the photoacoustic effect, conferring orders-of-magnitude improvement in optical excitation power. Additionally, the wide selectivity of the system arises from the inherent broad tunability and narrow optical linewidth of an OPO. Here we report the use of this technology for the detection of ammonia (NH3) as a simulant target molecule. A 3-D printed miniature PAS cell with microelectromechanical systems based (MEMS) microphone is used for the gas detection. The resonance frequency of the cell was measured at 17.9 kHz with a Q-factor of 9. The down-converted signal wave resonating within its optical cavity was tuned to 6605.6cm-1 (corresponding to a strong local NH3 absorption line) through a combination of phase matching and intra-cavity etalon control. The laser was amplitude modulated at the resonance frequency of the PAS cell, producing an average optical excitation power of ~10W in the signal arm of the OPO, to induce the photoacoustic effect for only 4W of primary diode pump power. In this work we show detection limit at the level of single parts-per-billion (ppb). Additionally, we will discuss how this technology could be readily refined to potentially demonstrate a sensitivity of tens parts-per-quadrillion

De eenheid van het recht : enkele beschouwingen over specialisatie in de rechtswetenschap

Rede. Landbouwhogeschool te Wageningen. 25 Februari 195

Classification for hyperspectral imaging

Hyperspectral Imaging is a method of collecting and processing the information across pre-defined electromagnetic spectrum. These measurements make it possible to derive a continuous spectrum for each pixel of the image. After necessary adjustments these image spectra can be compared with database of reflectance spectra in order to recognise tested materials. This project is conducted in cooperation between Fraunhofer Centre for Applied Photonics and Heriot-Watt Industrial Doctorate Centre in Photonics and Optics Technologies in partnership with University of Strathclyde. Fraunhofer Institute is known of world-class photonics solutions and this project aims in enhancement of one of their Hyperspectral Imaging systems with signal processing techniques. Set of classification procedures would be applied for the output of imaging spectrometer with the intention of spatial and spectral classification of objects captured by the spectrometer. Spatial classification is based on Support Vector Machine (SVM) classifier. Use of texture features of the objects is considered as a base for labelling of detected items. Spectral classification is based on Partial Least Squares (PLS) method. With database of calibration reflectance spectra, method this can be used for prediction of “end members” concentration and therefore identification of the objects captured on the hyperspectral image.

Expanded Access as a source of real-world data: An overview of FDA and EMA approvals

Aims: To identify, characterize and compare all Food and Drug Administration (FDA) and European Medicines Agency (EMA) approvals that included real-world data on efficacy from expanded access (EA) programmes. Methods: Cross-sectional study of FDA (1955–2018) and EMA (1995–2018) regulatory approval documentation. We automated searching for terms related to EA in 22,506 documents using machine learning techniques. We included all approvals where EA terms appeared in the regulatory documentation. Our main outcome was the inclusion of EA data as evidence of clinical efficacy. Characterization was based on approval date, disease area, orphan designation and whether the evidence was supportive or pivotal. Results: EA terms appeared in 693 out of 22,506 (3.1%) documents, which referenced 187 approvals. For 39 approvals, data from EA programmes were used to inform on clinical efficacy. The yearly number of approvals with EA data increased from 1.25 for 1993–2013 to 4.6 from 2014–2018. In 13 cases, these programmes formed the main evidence for approval. Of these, patients in EA programmes formed over half (median 71%, interquartile range: 34–100) of the total patient population available for efficacy evaluation. Almost all (12/13) approvals were granted orphan designation. In 8/13, there were differences between regulators in approval status and valuation of evidence. Strikingly, 4 treatments were granted approval based solely on efficacy from EA. Conclusion: Sponsors and regulators increasingly include real-world data from EA programmes in the efficacy profile of a treatment. The indications of the approved treatments are characterized by orphan designation and high unmet medical need

Remote oil spill detection and monitoring on ice-covered waters

The spillage of oil in Polar Regions is particularly serious due to the threat to the environment and the difficulties in detecting and tracking the full extent of the oil seepage beneath the sea ice. Development of fast and reliable sensing techniques is highly desirable. In this paper hyperspectral imaging is proposed as a potential tool to detect the presence of oil beneath the sea ice. A feasibility study project was initiated to explore the detectability of the oil under ice layer. Some preliminary results obtained during this project are discussed

Inflammation and endothelial dysfunction are associated with retinopathy: the Hoorn study

AIMS/HYPOTHESIS: The exact pathogenesis of retinopathy in diabetic and non-diabetic individuals is incompletely understood, but may involve chronic low-grade inflammation and dysfunction of the vascular endothelium. The aim of this study was to investigate the association of inflammation and endothelial dysfunction with prevalent retinopathy in individuals with and without type 2 diabetes. METHODS: As part of a population-based cohort study, 625 individuals aged 50-74 years, stratified according to age, sex and glucose tolerance status, underwent an extensive physical examination. Retinopathy was assessed by an ophthalmological examination, including funduscopy and two-field 45 degrees fundus photography with mydriasis in both eyes. Levels of C-reactive protein (CRP), soluble intercellular adhesion molecule-1 (sICAM-1), von Willebrand factor, and soluble vascular adhesion molecule-1 (sVCAM-1) were assessed, together with the urinary albumin : creatinine ratio, and the results were combined to obtain summarising z scores for inflammation and endothelial dysfunction. RESULTS: The prevalence of retinopathy was positively associated with tertiles of CRP and sICAM-1. When compared with the lowest tertile, the highest tertile of the inflammatory z score was associated with retinopathy in all subjects (odds ratio [OR]=2.2, 95% CI 1.2-4.1, adjusted for age, sex and glucose tolerance status). The highest tertile of the endothelial dysfunction z score was associated with retinopathy among diabetic individuals (OR=4.4, 95% CI 1.2-15.9, adjusted for age and sex) but not in non-diabetic individuals. Additional adjustment for other risk factors, such as systolic and diastolic blood pressure, BMI, total cholesterol and triglycerides, or mutual adjustment of the inflammatory and endothelial dysfunction z scores did not change the results. CONCLUSIONS/INTERPRETATION: In this study, inflammatory activity and endothelial dysfunction were associated with retinopathy, which suggests their involvement in the pathogenesis of retinopath