A preliminary study of the effects of pH upon fluorescence in suspensions of prevotella intermedia

© 2016 Hope et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.The quantification of fluorescence in dental plaque is currently being developed as a diagnostic tool to help inform and improve oral health. The oral anaerobe Prevotella intermedia exhibits red fluorescence due to the accumulation of porphyrins. pH affects the fluorescence of abiotic preparations of porphyrins caused by changes in speciation between monomers, higher aggregates and dimers, but this phenomenon has not been demonstrated in bacteria. Fluorescence spectra were obtained from suspensions of P. intermedia that were adjusted to pHs commensurate with the range found within dental plaque. Two fluorescent motifs were identified; 410 nm excitation / 634 nm emission (peak A) and 398 nm excitation / 622 nm emission (peak B). A transition in the fluorescence spectra was observed from peak A to peak B with increasing pH which was also evident as culture age increased from 24 hours to 96 hours. In addition to these 'blue-shifts', the intensity of peak A increased with pH whilst decreasing with culture age from 24 to 96 hours. A bacterium's relationship with the local physiochemical environment at the time of image capture may therefore affect the quantification of dental plaque fluorescence

Unmixing water and mud: Characterizing diffuse boundaries of subtidal mud banks from individual satellite observations

This is the final version. Available from Elsevier via the DOI in this record. Mapping of subtidal banks in mud-dominated coastal systems is crucial as they influence not only shoreline and ecosystem dynamics but also economic activities and livelihoods of local communities. Due to associated spatiotemporal variations in suspended particulate matter concentrations, subtidal mudbanks are often confined by diffuse and rapidly changing boundaries. To avoid inaccurate representations of these mudbanks in remote sensing images, it is necessary to unmix distinctive reflectance signals into representative landcover fractions. Yet, extracting mud fractions, in order to characterize such diffuse boundaries, is challenging because of the spectral similarity between subtidal- and intertidal features. Here we show that an unsupervised decision tree, used to derive spatially explicit and spectrally coherent image endmembers, facilitates robust linear spectral unmixing on an image-to-image basis, enabling the separation of these coastal features. We found that resulting abundance maps represent cross-shore gradients of vegetation, water and mud fractions present at the coast of Suriname. Furthermore, we confirmed that it is possible to separate land, water and an initial estimate of intertidal zones on individual images. Thus, spectral signatures of end-member candidates, determined from relevant index histograms within these initial estimates, are consistent. These results demonstrate that spectral information from well-defined spatial neighbourhoods facilitates the detection of diffuse boundaries of mudbanks with a spectral unmixing approach.NWO WOTR

The evaluation of a novel method comparing quantitative light-induced fluorescence (QLF) with spectrophotometry to assess staining and bleaching of teeth

This study reports the development and evaluation of a novel method using quantitative light-induced fluorescence (QLF), which enables its use for quantifying and assessing whole tooth surface staining and tooth whitening. The method was compared with a spectrophotometer to assess reliability. Two experimental phases, intrinsic stain formation and tooth whitening, were conducted in vitro on 16 extracted bovine teeth. Intrinsic stains were developed via access through lingual surfaces and root canals of these teeth using tea solution (2 g/100 ml, Marks and Spencer Extra Strong Tea, Marks and Spencer, London, UK) for 6 days. Stains were removed using 33% hydrogen peroxide (VWR Prolab, Leicestershire, UK) in cycles over 150 min. Stain development/whitening was monitored with QLF (Inspektor Research systems, Amsterdam, Netherlands) and spectrophotometry (Easy shade, Vita Zahnfabrik, Bad Säckingen, Germany). Parameters Delta F for QLF and Delta E for the spectrophotometer were obtained. The progression of stain intensity and removal observed by the methods were tested for correlation using Pearson's correlation coefficient. Intra-examiner reliability for each method was tested. QLF showed a high correlation with spectrophotometry for detecting and monitoring intrinsic tooth stain progression (Pearson coefficient r was −0.987 with correlation significant p < 0.0001). For stain removal, the Pearson coefficient (r) between both methods was −0.906 with no significance p = 0.094. The use of an external reference material in combination with the inner patch QLF analysis technique had the ability to detect and measure whole tooth surface staining and its removal longitudinally. The reliability of the method shows a potential clinical application

Can HRCT be used as a marker of airway remodelling in children with difficult asthma?

BACKGROUND: Whole airway wall thickening on high resolution computed tomography (HRCT) is reported to parallel thickening of the bronchial epithelial reticular basement membrane (RBM) in adult asthmatics. A similar relationship in children with difficult asthma (DA), in whom RBM thickening is a known feature, may allow the use of HRCT as a non-invasive marker of airway remodelling. We evaluated this relationship in children with DA. METHODS: 27 children (median age 10.5 [range 4.1-16.7] years) with DA, underwent endobronchial biopsy from the right lower lobe and HRCT less than 4 months apart. HRCTs were assessed for bronchial wall thickening (BWT) of the right lower lobe using semi-quantitative and quantitative scoring techniques. The semi-quantitative score (grade 0-4) was an overall assessment of BWT of all clearly identifiable airways in HRCT scans. The quantitative score (BWT %; defined as [airway outer diameter - airway lumen diameter]/airway outer diameter x100) was the average score of all airways visible and calculated using electronic endpoint callipers. RBM thickness in endobronchial biopsies was measured using image analysis. 23/27 subjects performed spirometry and the relationships between RBM thickness and BWT with airflow obstruction evaluated. RESULTS: Median RBM thickness in endobronchial biopsies was 6.7(range 4.6-10.0) microm. Median qualitative score for BWT of the right lower lobe was 1(range 0-1.5) and quantitative score was 54.3 (range 48.2-65.6)%. There was no relationship between RBM thickness and BWT in the right lower lobe using either scoring technique. No relationship was found between FEV1 and BWT or RBM thickness. CONCLUSION: Although a relationship between RBM thickness and BWT on HRCT has been found in adults with asthma, this relationship does not appear to hold true in children with D

Ultrasonic characterization of ultrasound contrast agents

The main constituent of an ultrasound contrast agent (UCA) is gas-filled microbubbles. An average UCA contains billions per ml. These microbubbles are excellent ultrasound scatterers due to their high compressibility. In an ultrasound field they act as resonant systems, resulting in harmonic energy in the backscattered ultrasound signal, such as energy at the subharmonic, ultraharmonic and higher harmonic frequencies. This harmonic energy is exploited for contrast enhanced imaging to discriminate the contrast agent from surrounding tissue. The amount of harmonic energy that the contrast agent bubbles generate depends on the bubble characteristics in combination with the ultrasound field applied. This paper summarizes different strategies to characterize the UCAs. These strategies can be divided into acoustic and optical methods, which focus on the linear or nonlinear responses of the contrast agent bubbles. In addition, the characteristics of individual bubbles can be determined or the bubbles can be examined when they are part of a population. Recently, especially optical methods have proven their value to study individual bubbles. This paper concludes by showing some examples of optically observed typical behavior of contrast bubbles in ultrasound fields

Imaging spontaneous currents in superconducting arrays of pi-junctions

Superconductors separated by a thin tunneling barrier exhibit the Josephson effect that allows charge transport at zero voltage, typically with no phase shift between the superconductors in the lowest energy state. Recently, Josephson junctions with ground state phase shifts of pi proposed by theory three decades ago have been demonstrated. In superconducting loops, pi-junctions cause spontaneous circulation of persistent currents in zero magnetic field, analogous to spin-1/2 systems. Here we image the spontaneous zero-field currents in superconducting networks of temperature-controlled pi-junctions with weakly ferromagnetic barriers using a scanning SQUID microscope. We find an onset of spontaneous supercurrents at the 0-pi transition temperature of the junctions Tpi = 3 K. We image the currents in non-uniformly frustrated arrays consisting of cells with even and odd numbers of pi-junctions. Such arrays are attractive model systems for studying the exotic phases of the 2D XY-model and achieving scalable adiabatic quantum computers.Comment: Pre-referee version. Accepted to Nature Physic

Mapping mangrove dynamics and colonization patterns at the Suriname coast using historic satellite data and the LandTrendr algorithm

This is the final version. Available from Elsevier via the DOI in this record. Mangroves play an important role in protecting coasts against wave energy and storms. Mangrove ecosystems provide important habitats for fauna and flora and are an important carbon sink. Loss of mangroves forest may lead to enhanced coastal erosion. Mangroves are complex ecosystems and processes of settling and development are not fully understood. Characterizing the rates and patterns of mangrove gains and losses is needed to better understand the functioning of mangrove ecosystems, how mangrove dynamics are linked to coastal morphological behaviour and how human interference with the coastal system impacts mangroves. Here we present a study of the mangrove ecosystems at the Suriname coast, which are relatively pristine and characterized by strong dynamics due to migrating mudbanks along the coast. Satellite images between 2000 and 2018, available in the historic satellite image archives, were analysed using the LandTrendr (Landsat-based detection of trends in disturbance and recovery) algorithm to identify locations of mangrove erosion, mangrove colonization, surface areas of change and patterns of settlement, as indicated by (sudden) changes in NDVI. The algorithm requires careful setting of various parameters for successful detection of (abrupt) temporal changes in mangrove coverage. The algorithm was evaluated on its robustness using various parameter settings. Results show the value of the timeseries of Landsat imagery to detect locations of coastal erosion of up to 50 m/yr and accretion where loss or settlement of mangroves is prevailing between 2000 and 2018. Locally differences are very large. An overall westward mangrove progression along the coast is apparent from the images and probably linked to mud bank migration. Various patterns of mangrove colonization and development such as arc-, zonal- and patch- arrangements were identified, although at some locations the Landsat resolution of 30 m is somewhat coarse to allow detailed analysis. The success and robustness of the LandTrendr algorithm are controlled by NDVI threshold values, number of allowed breakpoints in the timeseries and fitting parameters. The presented method requires further testing and evaluation but is a promising tool for semi-automatic detection of coastal mangrove erosion and colonization that can be applied to other mangrove ecosystems in the world. The satellite timeseries analyses generate valuable information on coastal dynamics, which is helpful to identify coastal areas prone to erosion and mangrove retreat and provide as such a valuable tool for coastal management and protection.NWO WOTRO Joint Sustainability Development Goal Research ProgramUtrecht University Bright Minds projec

Shot noise in mesoscopic systems

This is a review of shot noise, the time-dependent fluctuations in the electrical current due to the discreteness of the electron charge, in small conductors. The shot-noise power can be smaller than that of a Poisson process as a result of correlations in the electron transmission imposed by the Pauli principle. This suppression takes on simple universal values in a symmetric double-barrier junction (suppression factor 1/2), a disordered metal (factor 1/3), and a chaotic cavity (factor 1/4). Loss of phase coherence has no effect on this shot-noise suppression, while thermalization of the electrons due to electron-electron scattering increases the shot noise slightly. Sub-Poissonian shot noise has been observed experimentally. So far unobserved phenomena involve the interplay of shot noise with the Aharonov-Bohm effect, Andreev reflection, and the fractional quantum Hall effect.Comment: 37 pages, Latex, 10 figures (eps). To be published in "Mesoscopic Electron Transport," edited by L. P. Kouwenhoven, G. Schoen, and L. L. Sohn, NATO ASI Series E (Kluwer Academic Publishing, Dordrecht