Search results for "Spectroscopy"

Conductive and Capacitive Properties of the Bipolar Membrane Junction Studied by AC Impedance Spectroscopy

2001

The complete ac impedance spectrum of four bipolar membranes is analyzed both theoretically and experimentally taking into account both ionic transport and water dissociation together with the structural aspects of the bipolar junction. A theoretical model based on the Nernst-Planck and Poisson equations for the conductive and capacitive properties of the junction provides a qualitative description of the bipolar membranes for a broad range of electric currents and temperatures. Special attention is paid to the characteristics of the bipolar junction structure and the contact region between the two ion-exchange layers. It is observed that the effective area of this region increases with the…

Visible-NIR reflectance spectroscopy and manifold learning methods applied to the detection of fungal infections on citrus fruit

2015

Abstract The development of systems for automatically detecting decay in citrus fruit during quality control is still a challenge for the citrus industry. The feasibility of reflectance spectroscopy in the visible and near infrared (NIR) regions was evaluated for the automatic detection of the early symptoms of decay caused by Penicillium digitatum fungus in citrus fruit. Reflectance spectra of sound and decaying surface parts of mandarins cv. ‘Clemenvilla’ were acquired in two different spectral regions, from 650 nm to 1050 nm (visible–NIR) and from 1000 nm to 1700 nm (NIR), pointing to significant differences in spectra between sound and decaying skin for both spectral ranges. Three diffe…

Cluster formation and rheology of photoreactive nanoparticle dispersions.

2008

We show how photocrosslinking of small nanoparticles within a very dilute colloidal dispersion leads to the formation of large fractal particle clusters, which have a strong influence on the viscosity of the dispersion although the overall solid content is well below 5 wt %. Furthermore, the solvent plays an important role because of its function as an optical filter, for example, in toluene only photocrosslinking but no photocleavage takes place. Therefore, a diffusion-controlled cluster growth mechanism, leading to clusters with low fractal dimension, is expected; on the other hand, in tetrahydrofuran the photoreaction is partially reversible. Therefore, the cluster growth in this case is…

Measurement of haemodynamics of exercising and non-exercising vastus lateralis muscle with hybrid diffuse optics

2016

We present simultaneous diffuse correlation spectroscopy (DCS) and time resolved spectroscopy (TR NIRS) measurements on exercising and non-exercising vastus lateralis muscle. We discuss the results at two different exercise levels.

Lateral flow assays towards point-of-care cancer detection: A review of current progress and future trends

2020

Abstract Cancer is one of the main causes of mortality and morbidity worldwide. However, its early non-invasive detection via quantification of appropriate biomarkers can significantly reduce mortality, enhance survival, and save treatment costs. Lateral flow test strips (LFTS) are nowadays considered as the most attractive point-of-care devices for healthcare applications. However, the quantification of cancer biomarkers in body fluids suffers from some challenges including i) the necessity for multiplex analysis, ii) the development of sensitive detection systems, iii) to overcome the analysis of complex samples, at the same time, it should keep the quality assurance criteria for an accur…

Design and development of a fNIRS system prototype based on SiPM detectors

2014

Functional Near Infrared Spectroscopy (fNIRS) uses near infrared sources and detectors to measure changes in absorption due to neurovascular dynamics in response to brain activation. The use of Silicon Photomultipliers (SiPMs) in a fNIRS system has been estimated potentially able to increase the spatial resolution. Dedicated SiPM sensors have been designed and fabricated by using an optimized process. Electrical and optical characterizations are presented. The design and implementation of a portable fNIRS embedded system, hosting up to 64 IR-LED sources and 128 SiPM sensors, has been carried out. The system has been based on a scalable architecture whose elementary leaf is a flexible board …

Non-invasive analysis of solid samples

2013

Within the Green Analytical Chemistry paradigm, the best alternative for greening the methods of analysis comprises the direct determination of sample composition and/or sample properties without any chemical sample treatment, and, of course, it would be preferable not to have any physical treatment before acquisition of the information desired. In this review, we evaluate the state of the art in, and available alternatives for, analysis of solids without prior sample treatment, starting from the non-invasive quality control of products or processes through to the use of portable instruments for in situ determinations and the development of methods based on image analysis. We evaluate the a…

Characterization of petroleum-based products by infrared spectroscopy and chemometrics

2012

Abstract The role of fossil fuels in providing the energy required for automobiles, factories and daily life has seriously concerned the authorities. Consistency of the quality of petroleum-based products is an important aspect of social and environmental criteria in a developed society. High-quality petroleum-based fuels would have several benefits (e.g., reduction in rate of consumption, less environmental pollution and durability of hardware). We review recent advances in the application of infrared spectroscopy in the petroleum industry. We focus on the methods proposed for the determination of a wide range of characteristics in petroleum-based products. We discuss methods based on the …

Current issues in hyperpolarized gases in MRI: biomedical investigations and clinical applications

2000

Progress in analysis of residual antibacterials in food

2007

Abstract Residual antibacterials in food constitute a risk to human health. Although epidemiological data on the real magnitude of their adverse effects are very scarce, they indicate that food could be an important avenue for evolution and dissemination of antibiotic-resistant bacteria. Analysis of these residues plays a key role in ensuring food safety, to the point that the European Union has not only established maximum residue limits but also requirements concerning the performance of analytical methods and the interpretation of the results. These specifications have had a great influence on protocols and techniques applied. In this review, we discuss the progress of rapid screening me…