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Light-induced degradation (LID) strongly depends on experimental conditions, among which the presence of oxygen is a major parameter. Elucidating LID processes is of high concern to many areas of interest, e.g., for the conservation of cultural heritage, safety and shelf life of food, and UV-disinfection methods for water purification. Recently, we presented a new, fully automated tool to study molecular photodegradation in solution. The tool employs a gas-permeable liquid-core waveguide (LCW) as a light-exposure cell with in-situ absorption spectroscopy for real-time monitoring, coupled on-line to liquid chromatography (LC) with diode-array (DAD) and mass spectrometry (MS) for characterization of the photodegradation products. The current work reports on the assessment of the potential of the LCW in a tube-in-tube geometry for studying the role of oxygen in photodegradation processes, using Riboflavin and Eosin Y as model compounds. The LID results obtained for Riboflavin and Eosin Y using the LCW set-up were in line with reported data obtained with conventional approaches. On-line LC-MS analysis allowed semi-quantitative monitoring of LID differences under oxic and anoxic circumstances. An increase in degradation by 9% and 30% for Riboflavin and Eosin Y, respectively, was observed after 10 min under anoxic conditions. Moreover, for the first time, the fully debrominated species of Eosin Y (i.e. fluorescein), was identified as a photodegradation product in solution. The presented set-up can be highly useful for the investigation of photodegradation mechanisms and kinetics in solution, including the role of oxygen while increasing analytical efficiency and reducing time spent in the lab.

There is increasing evidence of altered tissue mechanics in neurodegeneration. However, due to difficulties in mechanical testing procedures and the complexity of the brain, there is still little consensus on the role of mechanics in the onset and progression of neurodegenerative diseases. In the case of Alzheimer’s disease (AD), magnetic resonance elastography (MRE) studies have indicated viscoelastic differences in the brain tissue of AD and healthy patients. However, there is a lack of viscoelastic data from contact mechanical testing at higher spatial resolution. Therefore, we report viscoelastic maps of the hippocampus obtained by a dynamic indentation on brain slices from the APP/PS1 mouse model where individual brain regions are resolved. A comparison of viscoelastic parameters shows that regions in the hippocampus of the APP/PS1 mice are significantly stiffer than wild-type (WT) mice and have increased viscous dissipation. Furthermore, indentation mapping at the cellular scale directly on the plaques and their surroundings did not show local alterations in stiffness although overall mechanical heterogeneity of the tissue was high (SD~40%). Therefore, reported mechanical alterations at a tissue scale indicates global remodeling of the brain tissue structure.

As the typical surface separations in Micro Electro-Mechanical Systems (MEMS) are reduced to below one micrometer, detailed knowledge of the interaction forces down to this scale is required. In this context, we have developed a dedicated experimental platform to directly investigate electrostatic and physical effects in a high-aspect-ratio electrostatic-capacitive MEMS device based on commercial technology. In the present work, we report on an extensive experimental characterization, focused on the influence of the surface separations, electric surface potentials, and pressure on the static and dynamical behaviour of the device under precisely controlled conditions. For the proper analysis of the bias position and small-displacement response of the device, we have developed a comprehensive electro-mechanical model capable of describing the aforementioned effects, and allowing to extract the mechanical and electrical device parameters from the experimental data. Based on the developed model, a strong experimental evidence is found for significant variations in device characteristics upon reduction of surface separation to below one micrometer. (C) 2017 Elsevier B.V. All rights reserved.

The dynamic response of a MEMS accelerometer can be influenced by several multi-physics effects, especially if the gaps between the shuttle and the stator attain sub-micrometric values. The present paper aims at tackling the aforementioned issues by means of a suitable experimental procedure, which has been purposely devised for the problem at hand, and through the execution of numerical analyses (based on the Finite Element Model). The effect of parasitic electrostatic forces and hydrodynamic forces is clearly demonstrated.

In recent years visible pump/mid-infrared (IR) probe spectroscopy has established itself as a key technology to unravel structure–function relationships underlying the photo-dynamics of complex molecular systems. In this contribution we review the most important applications of mid-infrared absorption difference spectroscopy with sub-picosecond time-resolution to photosynthetic complexes. Considering several examples, such as energy transfer in photosynthetic antennas and electron transfer in reaction centers and even more intact structures, we show that the acquisition of ultrafast time resolved mid-IR spectra has led to new insights into the photo-dynamics of the considered systems and allows establishing a direct link between dynamics and structure, further strengthened by the possibility of investigating the protein response signal to the energy or electron transfer processes. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems.

Purpose: Only an endophytic growth pattern in juxtapapillary retinal hemangioblastoma (JRH) is an indication for surgical treatment, but classification of growth types is difficult using conventional imaging techniques. This case report describes the use of optical coherence tomography angiography (OCT-A) features for classification and treatment follow-up in a case with JRH. Observations: The JRH of this patient was easily detected with two different OCT-A methods in both en-face and cross-sectional B-scan images, and was classified as a sessile growth type. This growth type excluded the treatment option of vitreoretinal surgery with excision of the lesion or ligation of the feeder vessels. The patient was treated multiple times with intravitreal bevacizumab. Treatment follow-up with OCT-A initially revealed a stable extent of the JRH, with some slight flow deviations in en-face visualization, followed by a period of progressive growth of the lesion. Conclusions: OCT-A revealed the depth localization of the JRH and seems to be a valuable tool for JRH classification. Detailed classification may be useful when surgery is considered as a treatment strategy. Furthermore, treatment follow-up is possible with OCT-A, although imaging artifacts should be taken into account. Keywords: Juxtapapillary retinal hemangioblastoma, Optical coherence tomography angiography, Doppler OCT, Intravitreal bevacizumab, Sessile

We present a numerical analysis of an air flow velocity sensor based on a fiber-optic ferrule-top cantilever. The device forms a low-finesse Fabry-Perot interferometer, with one of the two reflecting surfaces constituted by a cantilever beam. Under the effect of the flow pressure, the cantilever bends producing a change in the cavity length of the Fabry-Perot and therefore a modification of its optical response. The numerical analysis, performed by use of finite-element method (FEM), is then compared with a set of experimental results obtained in a small wind-tunnel. © 2012 Elsevier B.V.

The analysis of simultaneous EEG and fMRI data is generally based on the extraction of regressors of interest from the EEG, which are correlated to the fMRI data in a general linear model setting. In more advanced approaches, the spatial information of EEG is also exploited by assuming underlying dipole models. In this study, we present a semi automatic and efficient method to determine electrode positions from electrode gel artifacts, facilitating the integration of EEG and fMRI in future EEG/fMRI data models. In order to visualize all electrode artifacts simultaneously in a single view, a surface rendering of the structural MRI is made using a skin triangular mesh model as reference surface, which is expanded to a "pancake view". Then the electrodes are determined with a simple mouse click for each electrode. Using the geometry of the skin surface and its transformation to the pancake view, the 3D coordinates of the electrodes are reconstructed in the MRI coordinate frame. The electrode labels are attached to the electrode positions by fitting a template grid of the electrode cap in which the labels are known. The correspondence problem between template and sample electrodes is solved by minimizing a cost function over rotations, shifts and scalings of the template grid. The crucial step here is to use the solution of the so-called "Hungarian algorithm" as a cost function, which makes it possible to identify the electrode artifacts in arbitrary order. The template electrode grid has to be constructed only once for each cap configuration. In our implementation of this method, the whole procedure can be performed within 15 min including import of MRI, surface reconstruction and transformation, electrode identification and fitting to template. The method is robust in the sense that an electrode template created for one subject can be used without identification errors for another subject for whom the same EEG cap was used. Furthermore, the method appears to be robust against spurious or missing artifacts. We therefore consider the proposed method as a useful and reliable tool within the larger toolbox required for the analysis of co-registered EEG/fMRI data. © 2011 Elsevier Inc.

It is now quite well accepted that charge separation in PS2 reaction centers starts predominantly from the accessory chlorophyll BA and not from the special pair P680. To identify spectral signatures of BA, and to further clarify the process of primary charge separation, we compared the femtosecond-infrared pump-probe spectra of the wild-type (WT) PS2 core complex from the cyanobacterium Synechocystis sp. PCC 6803 with those of two mutants in which the histidine residue axially coordinated to PB (D2-His197) has been changed to Ala or Gln. By analogy with the structure of purple bacterial reaction centers, the mutated histidine is proposed to be indirectly H-bonded to the C9=O carbonyl of the putative primary donor BA through a water molecule. The constructed mutations are thus expected to perturb the vibrational properties of BA by modifying the hydrogen bond strength, possibly by displacing the H-bonded water molecule, and to modify the electronic properties and the charge localization of the oxidized donor \documentclass[10pt]{article} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{pmc} \usepackage[Euler]{upgreek} \pagestyle{empty} \oddsidemargin -1.0in \begin{document} \begin{equation*}{\mathrm{P}}_{680}^{+}.\end{equation*}\end{document} Analysis of steady-state light-induced Fourier transform infrared difference spectra of the WT and the D2-His197Ala mutant indeed shows that a modification of the axially coordinating ligand to PB induces a charge redistribution of \documentclass[10pt]{article} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{pmc} \usepackage[Euler]{upgreek} \pagestyle{empty} \oddsidemargin -1.0in \begin{document} \begin{equation*}{\mathrm{P}}_{680}^{+}.\end{equation*}\end{document} In addition, a comparison of the time-resolved visible/midinfrared spectra of the WT and mutants has allowed us to investigate the changes in the kinetics of primary charge separation induced by the mutations and to propose a band assignment identifying the characteristic vibrations of BA.

The paper analyses generator operations of asynchronous machines when they are connected to a passive electrical network either directly or by an intermediate static power converter. The analysis is performed by taking into account the saturation phenomena of the main magnetic circuits of the machine. Mathematical models of both physical configurations are given and their non-linearities are evidenced. The paper investigates the existence of periodical solutions related to stable operations of the systems. Numerical and experimental results support the theoretical analysis.

We report on the study of infrared emission from gaseous argon excited by MeV protons in the wavelength range 0.7-1.8 mun. The dependence of the light yield on the applied electric field has been measured at different pressures. At zero held (prompt emission) the yield does not depend on pressure. When a field is applied the light emission increases linearly with the field strength above a critical value (drift emission) and a dependence from pressure is observed. Prompt and drift emission are consistent with transitions between the lowest atomic states of neutral argon. Drift emission is generated by electrons which gain energy from the electric field and excite atoms through collisions. (C) 2001 Elsevier Science B.V. All rights reserved.

Purpose To study patients diagnosed with retinal angiomatous proliferation (RAP) based on conventional imaging techniques with phase-resolved Doppler optical coherence tomography (OCT) to detect and localize blood flow in RAP lesions; and to compare these findings to conventional imaging, which are mostly invasive and give limited information concerning intra- and transretinal blood flow. Design Single-center, consecutive observational case series. Methods Twelve treatment-naive patients diagnosed with RAP based on fundus examination, fluorescein angiography, and indocyanine green angiography were included. Median age was 79 years (range 65–90). Patients were imaged with an experimental 1040 nm swept-source phase-resolved Doppler OCT instrument. Abnormal flow was defined as intraretinal neovascularization or retinal choroidal anastomosis. Results In 11 patients adequate phase-resolved Doppler OCT images were obtained showing abnormal blood flow in the RAP lesion. In 4 patients a retinal choroidal anastomosis was found, 3 patients showed intraretinal neovascularization connected with a pigment epithelial detachment, 2 patients showed only intraretinal neovascularization, and in 2 patients flow was limited to the subretinal or sub–retinal pigment epithelial space. Conclusions Phase-resolved Doppler OCT is able to detect and localize abnormal blood flow within RAP lesions. Blood flow was mostly confined to the intraretinal structures with or without a connecting pigment epithelial detachment; in one-third of patients a retinal choroidal anastomosis was detected. The potential of angiography with phase-resolved Doppler OCT to accurately distinguish between normal and pathologic blood flow in addition to structural OCT data without invasive procedures will help to further elucidate both retinal and choroidal vascular pathologies like RAP.

Light yield and spectrum of infrared (IR) scintillation in Xe are different in gaseous and liquid phases. In gas, the spectrum consists mainly of a broad line centered at 1300 nm. In liquid, light is emitted primarily below 1200 nm and with a lower yield. (C) 2001 Elsevier Science B.V. All rights reserved.

High Performance Liquid Chromatography combined with fluorescence detection is routinely used in the Dutch Water Quality Survey to determine the Polycyclic Aromatic Hydrocarbons (PAH) contents of marine sediment samples. In this paper Shpol'skii spectroscopy is utilized to ascertain the identity and the purity of the peaks in the chromatogram by collection of several eluting fractions and subsequent spectroscopic analysis. The low temperature Shpol'skii technique provides high-resolution fluorescence spectra of PAHs that can serve as fingerprints. Thus, information concerning peak purity was obtained and the number of components identified was roughly doubled.

We present the results of an extensive characterization of physical and electrostatic effects influencing the dynamical behavior of a micro-electromechanical (MEMS) accelerometer based on commercial technology. A similar device has been utilized recently to demonstrate the effect of Casimir and other nano-scale interactions on the pull-in distance [Ardito et. al., Microelectron. Reliab., 52 (2012) 271]. In the present work, we focus on the influence of pressure, plate separation, and electric surface potentials on the spectral mechanical response. We finally find evidence for the presence of non-viscous damping due to compressibility of the ambient gas, and demonstrate a strong dependence of the sensitivity on the parameters of the operating point.

Purpose: To determine the diagnostic capability of spectral-domain optical coherence tomography in glaucoma patients with visual field defects. Design: Prospective, cross-sectional study. Methods: settings: Participants were recruited from a university hospital clinic. study population: One eye of 85 normal subjects and 61 glaucoma patients with average visual field mean deviation of -9.61 ± 8.76 dB was selected randomly for the study. A subgroup of the glaucoma patients with early visual field defects was calculated separately. observation procedures: Spectralis optical coherence tomography (Heidelberg Engineering, Inc) circular scans were performed to obtain peripapillary retinal nerve fiber layer (RNFL) thicknesses. The RNFL diagnostic parameters based on the normative database were used alone or in combination for identifying glaucomatous RNFL thinning. main outcome measures: To evaluate diagnostic performance, calculations included areas under the receiver operating characteristic curve, sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio. Results: Overall RNFL thickness had the highest area under the receiver operating characteristic curve values: 0.952 for all patients and 0.895 for the early glaucoma subgroup. For all patients, the highest sensitivity (98.4%; 95% confidence interval, 96.3% to 100%) was achieved by using 2 criteria: < 1 RNFL sectors being abnormal at the < 5% level and overall classification of borderline or outside normal limits, with specificities of 88.9% (95% confidence interval, 84.0% to 94.0%) and 87.1% (95% confidence interval, 81.6% to 92.5%), respectively, for these 2 criteria. Conclusions: Statistical parameters for evaluating the diagnostic performance of the Spectralis spectral-domain optical coherence tomography were good for early perimetric glaucoma and were excellent for moderately advanced perimetric glaucoma. © 2012 Elsevier Inc. All Rights Reserved.