Optical Fiber Catheter with Distal End Bending Mechanism Control for Raman Biospectroscopy

Abstract

This work proposes the development of an optical catheter with bending control of the distal end. The probe consists of seven optical fibers wrapped in a resin and a biocompatible flexible teflon tube with a novel mechanical device that allows bending of the distal extremity to access a desired location of a human organ. A central fiber is used for tissue Raman excitation, five fibers are used for Raman signal collection, and the seventh for “optoclinical” treatment applications. Infrared, dispersive Raman spectra at 785 nm excitation were employed to optically characterize the proposed catheter. An excitation transmission loss of 16% was found compared to the traditional six collecting fibers catheter, both with their distal tip straight. By bending of the distal tip at different angles, with turning the intermediated section of the catheter around cylinders of different diameters (one finds a correlation between curvature angle of the tip and cylinder diameter), the transmission loss coefficient and transmission were determined for each distal tip angle. A transmission reduction of 5% was found for a 180° curvature. This optical catheter could be very useful in clinics, providing a way to control the fiber tip position and angle onto the tissue or organ.     

USE OF DISPERSIVE RAMAN SPECTROSCOPY IN THE DETERMINATION OF UNSATURATED FAT IN COMMERCIAL EDIBLE OIL- AND FAT-CONTAINING INDUSTRIALIZED FOODS

The present study aims at the use of Raman spectroscopy in the quantification of unsaturated fats in fat-containing foods, compared to the information available in the Nutritional Table, to obtain a non-destructive optical quantification of unsaturation. Raman spectra of edible oil, margarine, mayonnaise, hydrogenated fat, and butter were obtained with a near-infrared Raman spectrometer (830 nm). By analyzing selected bands in the regions of 1750, 1660, 1440, 1300, and 1260 cm^?1, the amount of total and unsaturated fat of samples of oil, margarine, and mayonnaise were correlated with the information displayed in the Nutritional Table. The amount of unsaturated trans fat in selected samples was correlated to the Raman shift of 1660 cm^?1. Dispersive Raman spectroscopy was shown to be effective in quantifying the unsaturated fats in oil, margarine, and mayonnaise, and trans fat in hydrogenated oils and butter.     

Microscopic Characterization of FO/PRO Membranes - A Comparative Study of CLSM, TEM and SEM

Osmotically driven membrane processes (including forward osmosis (FO) and pressure retarded osmosis (PRO)) have received increasing attention in recent decades. The performance of an FO/PRO membrane is significantly limited by internal concentration polarization, which is a strong function of the membrane support layer pore structure. The objective of the current study was to develop microscopic characterization methods for quantitative/semiquantitative analysis of membrane pore structure (both pore diameter and porosity distribution across membrane thickness). The use of confocal laser scanning microscopy (CLSM) for noninvasive characterization of the internal pore structure of FO/PRO membranes is reported for the first time. By performing optical sectioning, information on pore diameter, porosity depth profile and pore connectivity can be obtained. The CLSM porosity results are further compared to those obtained using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and reasonably good agreement was observed. A comparison of these characterization methods reveals their complementary nature, and a combination of these techniques may allow a more comprehensive understanding of membrane structure. The current study also provided a comprehensive insight into the pore structure of commercially available FO/PRO membranes.     

Mercury contaminated systems under recovery can represent an increased risk to seafood human consumers – A paradox depicted in bivalves’ body burdens

The present study, carried out in a mercury (Hg) contaminated estuary, aimed to investigate: (i) the long-term evolution of the Hg bioavailability in the environmental matrices, in a period of 5 years (2003–2008), without new anthropogenic inputs; (ii) the temporal evolution of Hg load (organic and inorganic forms) in the native bivalve Scrobicularia plana, inferring the progression of human health risk associated to its consumption and the dependence on the animals’ size. The area selected was Laranjo basin of Ria de Aveiro (Portugal), where a Hg gradient was identified because of past discharges from a chlor-alkali plant. Two sites termed M (moderately contaminated) and H (highly contaminated) were compared with an uncontaminated reference (R) site. Results displayed a persistence of Hg in the environment, though the levels in sediment decreased at site H, confirming the ecosystem recovery. The risk associated to clam consumption remained stable in 2008 considering their total Hg (T-Hg) load and the limits established by public health authorities, though T-Hg levels significantly decreased at H site for size classes C3 (2 year) and C4 (4 year). Organic Hg (O-Hg) accumulation increased from 2003 to 2008, reaching threatening levels and suggesting an increased bioavailability of this Hg form. This evolution towards an increase of O-Hg accumulation was particularly prominent under a moderate contamination scenario (site M). Overall, it was demonstrated that a period of 5 years of ecosystem recovery was not enough to eliminate the risk to human consumers, highlighting Hg contamination in estuaries as a long-lasting legacy. Paradoxically, it was pointed out that in a given step of the long-term restoration process, occurring naturally in aquatic systems, the risk associated to bivalves’ consumption can appear augmented due to O-Hg accumulation increments.     

Nanostructure, Excitations, and Thermoelectric Properties of Bi2Te3-Based Nanomaterials

The effect of dimensionality and nanostructure on thermoelectric properties in Bi₂Te₃-based nanomaterials is summarized. Stoichiometric, single-crystalline Bi₂Te₃ nanowires were prepared by potential-pulsed electrochemical deposition in a nanostructured Al₂O₃ matrix, yielding transport in the basal plane. Polycrystalline, textured Sb₂Te₃ and Bi₂Te₃ thin films were grown at room temperature using molecular beam epitaxy and subsequently annealed at 250°C. Sb₂Te₃ films revealed low charge carrier density of 2.6?×?10¹⁹?cm^?3, large thermopower of 130???V?K^?1, and large charge carrier mobility of 402?cm²?V^?1?s^?1. Bi₂(Te_0.91Se_0.09)₃ and (Bi_0.26Sb_0.74)₂Te₃ nanostructured bulk samples were prepared from as-cast materials by ball milling and subsequent spark plasma sintering, yielding grain sizes of 50?nm and thermal diffusivities reduced by 60%. Structure, chemical composition, as well as electronic and phononic excitations were investigated by x-ray and electron diffraction, nuclear resonance scattering, and analytical energy-filtered transmission electron microscopy. Ab?initio calculations yielded point defect energies, excitation spectra, and band structure. Mechanisms limiting the thermoelectric figure of merit ZT for Bi₂Te₃ nanomaterials are discussed.     

Thermomorphological analysis of Al2O3/HDPE nanocomposites: One approach in function of the processing and vinyltrimethoxysilane (VTMS) content

The present study assesses the influence of processing and adding alumina (Al₂O₃) nanoparticles functionalized with vinyltrimethoxysilane (VTMS) on high‐density polyethylene (HDPE) matrix. The model proposed by Henk, Kortsen, and Kvarts is used to calculate the ideal alumina nanoparticle concentration, in order to provide a larger interface area with lower agglomeration. Two different processing techniques are used to add the alumina nanoparticles functionalized with VTMS to the HDPE: direct blending and masterbatches applying the same processing extrusion parameters'. The alumina's nanoparticle functionalization with VTMS is confirmed by Fourier transform infrared spectroscopy analysis. The MFI is measured and nanoparticles dispersion is evaluated by scanning electron microscopy and by energy dispersive spectroscopy. Thermal behavior is measured by thermogravimetric analysis and differential scanning calorimetry. The addition of Al₂O₃ nanoparticles increases the thermal stability of the nanocomposites. Functionalization with VTMS provides improve adhesion to the polymer matrix, while the masterbatch processing technique promotes better alumina nanoparticle dispersion in the HDPE matrix and produce high crystalline composites. © 2019 Society of Plastics Engineers POLYM. ENG. SCI., 59:1332–1343 2019. © 2019 Society of Plastics Engineers