Anatomical and Functional Correlates of Voice Quality in Tracheoesophageal Speech

The purpose of the current study was to assess the anatomic and functional correlates of voice quality in tracheoesophageal speech, with dynamic imaging studies of the neoglottis. Videofluoroscopy (providing a lateral view), digital high-speed endoscopy (providing a "birds-eye" view), and their relationships with perceptual evaluations of voice quality were investigated. Several significant relationships were found. Imaging with videofluoroscopy revealed that the following anatomic and functional parameters (established during phonation) are related to voice quality: presence of a neoglottic bar, regurgitation of barium, tonicity of the neoglottis, and minimal neoglottic distance. Furthermore, the index of the increase of the maximal subneoglottic distance from rest to phonation also showed a significant relationship with voice quality. Imaging with digital high-speed endoscopy revealed features relevant to voice quality, including amount of saliva, visibility of the origin of the neoglottis, shape of the neoglottis, and regularity of the vibration. Knowledge of the anatomic and functional correlates of tracheoesophageal voice quality provides prerequisite information for future (phono-) surgical and/or clinical improvements to the voice quality of postlaryngectomy (prosthetic) voice production.     

Cathode-supported micro-tubular SOFCs based on Nd1.95NiO4 + δ: Fabrication and characterisation of dip-coated electrolyte layers

Fabrication conditions to obtain dense electrolyte double layers on a porous micro-tubular cathode substrate were investigated. Porous tubes of a nickelate material, Nd_1.95NiO_4 + δ, were fabricated by cold-isostatic pressing (CIP) and sintering. Thin films of electrolyte powders Ce_0.9Gd_0.1O_1.95 (GDC) and Zr_0.89Sc_0.1Ce_0.01O_1.95 (SSZ) were applied by dip-coating in aqueous suspensions. Electrolyte powders had been attrition-milled to decrease their particle size and densification temperature. The quantity of polyacrylic acid (PAA) as dispersant was optimised by ζ-potential measurements. The densification behaviour was studied by dilatometry and SEM-imaging. A sintering temperature of 1250 °C was found to densify GDC whereas SSZ-layers remained slightly porous.     

Analysis of [U‐13C6]glucose in human plasma using liquid chromatography/isotope ratio mass spectrometry compared with two other mass spectrometry techniques

The use of stable isotope labelled glucose provides insight into glucose metabolism. The ¹³C‐isotopic enrichment of glucose is usually measured by gas chromatography/mass spectrometry (GC/MS) or gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). However, in both techniques the samples must be derivatized prior to analysis, which makes sample preparation more labour‐intensive and increases the uncertainty of the measured isotopic composition. A novel method for the determination of isotopic enrichment of glucose in human plasma using liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) has been developed. Using this technique, for which hardly any sample preparation is needed, we showed that both the enrichment and the concentration could be measured with very high precision using only 20 µL of plasma. In addition, a comparison with GC/MS and GC/IRMS showed that the best performance was achieved with the LC/IRMS method making it the method of choice for the measurement of ¹³C‐isotopic enrichment in plasma samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Liquid chromatography–mass spectrometry methods for urinary biomarker detection in metabonomic studies with application to nutritional studies

The effects of sample preparation and chromatographic method differences on the classification and recovery of metabolic biomarkers from UPLC‐MS measurements on urine samples of humans exposed to different dietary interventions have been investigated. Eight volunteers consumed three high‐fat meals (rich in saturated, monounsaturated and polyunsaturated fatty acids, respectively) in randomized order with a washout period in between. For each participant, urine samples were obtained prior to and at three timed intervals after each meal. Samples were processed either by dilution (1 : 4) or by liquid–liquid extraction and then run under two different gradient conditions. For each analysis method, a total of 96 observations (eight participants, four time points, three diets) were measured. The total ion count chromatograms were analyzed using partial‐least‐squares discriminant analysis. All three dietary classes could be discriminated irrespective of sample preparation and chromatographic method. However, the main discriminating metabolites varied according to sample preparation, indicating that sample treatment and chromatographic conditions influence the ability to extract biomolecular information. Diluted samples showed higher m/z compounds (ca 400 u) while liquid–liquid extraction samples showed low m/z at the same retention time span. Optimized methods for metabolite identification (e.g. organic acids) were statistically inferior to global screening for mixed compound identification, confirming that multiple compound class‐based metabolic profiles are likely to give superior metabonomic (diagnostic) classification, although great care has to be taken in the interpretation in relation to matrix effects. Copyright © 2009 John Wiley & Sons, Ltd.     

Improving the thermal dimensional stability of flexible polymer composite backing materials for ultrasound transducers

Novel ultrasound backing materials based on polymer composites with improved dimensional stability and low coefficient of thermal expansion are being developed and analyzed. For this purpose a filled epoxy resin (Stycast₁₂₆₅), a commonly used backing material, was considered reference material and polyurethane composites (PU₂₃₀₅, PU₂₃₅₀) were proposed as better alternatives. When compared to the reference, the PU₂₃₅₀ filled with a mixture of Al₂O₃ and tungsten exhibited an approximately 15 times lower glassy transition temperature and a 2.5 time lower longitudinal thermal expansion at 20 °C. This ensures that within the entire operational temperature range the backing material is flexible, minimizing the thermal stresses induced onto transducer elements soldered joints and piezoceramic core. For the same material, the attenuation at 5 MHz was similar to the reference material while at 7 and 8.5 MHz it was 33% and 54% higher respectively. From these analyses it is concluded that the newly developed polyurethane composites outperform the reference backing with respect to the thermal dimensional stability as well as to the damping properties. An integrated rigorous mechano-acoustical approach is being proposed as an appropriate passive material design path. It can be easily extended to any other passive materials used for ultrasound transducer conception.