Nonlinear behavior of vocal fold vibration: The role of coupling between the vocal folds

Coupling between the vocal folds is one of the nonlinear mechanisms allowing regulation and synchronization of mucosal vibration. The purpose of this study was to establish that modulations such as diplophonia and abnormalities observed in vocal signals that may be observed in some cases of laryngeal pathology can be considered as nonlinear behavior due to the persistence of some physical interaction (coupling). An experimental model using excised porcine larynx was designed to create tension asymmetry between the vocal folds and to obtain vocal signals with modulations. Signals were analyzed by spectral analysis and the phase portrait method. Results were compared with computer-generated synthetic signals corresponding to nonlinear combinations of sinusoid signals. Under these conditions, evidence of nonlinear behavior was detected in 85% of experimental signals. These findings were interpreted as a demonstration of vocal fold interaction. Based on these findings, the authors conclude that (1) coupling must be taken into account in physical models of laryngeal physiology, and that (2) methods of nonlinear dynamics may be used for objective voice analysis.     

Effects of risedronate in a rat model of osteopenia due to orchidectomy and disuse: densitometric, histomorphometric and microtomographic studies

Dual energy X-ray absorptiometry (DXA), histomorphometry and X-ray microtomography (microCT) were used to assess effects of risedronate and testosterone in a combined rat model of orchidectomy (ORX) and local paralysis induced by botulinum neurotoxin (BTX). Four groups of mature rats were studied for 1 month: SHAM operated; ORX and right hindlimb immobilization (BTX); ORX+BTX+risedronate or testosterone. Changes in bone and body composition were measured by DXA (BMC, lean and fat mass), histomorphometry (BV/TV(2D), Tb.Th and microarchitectural parameters) and microCT (BV/TV(3D), SMI and cortical parameters). ORX and BTX had additive effects on bone loss since differences were maximized on the immobilized bone. The decrease in BMC on the tibial metaphysis reached -33.6% vs. -11.3% in the non-immobilized limb. BV/TV and Tb.N decreased and Tb.Sp increased in both hindlimbs whereas Tb.Th was significantly lower only in the immobilized limb. Decrease of tibial cortical area and thickness was greater in the immobilized limb. Risedronate prevented BMC, BV/TV and architecture loss but not reduction in Tb.Th. Cortical bone was preserved only in the non-immobilized limb. Testosterone was unable to prevent trabecular and cortical bone loss, but it prevents loss of whole body lean mass. In conclusion, ORX and BTX resulted in additive effects on bone loss. Risedronate had protective effects on trabecular bone loss but was less effective on cortical bone.     

Edge-strengthening of flat glass with acrylate coatings

Edge-strengthening is a novel technology used to strengthen glass by applying a coating only on the edges. In this work, edge flaws of flat glass articles were examined in detail via scanning electron microscope (SEM) imaging. Then the effect of using weatherable acrylate coatings on edge-strengthening of flat glass was determined. Four-point bending measurement showed that the coatings provided more than twofold increase of the mean flexural strength and a factor of about two increase of the tensile stress needed to reach 0.8% cumulative probability of failure. The coatings were found to cover the flaw zone at the glass edges and partially fill in the cracks. Different surface treatments led to different levels of strengthening, indicating the importance of coating adhesion. The coating’s thermal and mechanical properties affected the extent of strengthening effect. A coating formulation with a higher glass transition temperature tended to provide a better strengthening effect, indicating the importance of closure stress within cracks generated during film curing process. Challenges of applying the edge-strengthening technology are also discussed.     

Optimization of capillary zone electrophoresis parameters for selenium speciation

The behaviour of four biologically relevant selenium compounds (Se(VI), Se(IV), selenomethionine and selenocystine) in capillary zone electrophoresis (CZE) was investigated. Parameters which affect the separation, detection and sample introduction were investigated to improve the sensitivity of the analysis. Short-term repeatability was evaluated and detection limits were found to be in the g·l^–1 range.     

Polarographic determination of aluminum in titanium alloys

Considerable interest has been shown in titanium metal because of its combination of desirable properties, including its favorable strength to weight ratio and its resistance to corrosion. Since titanium-aluminum alloys are fairly common, there is need for an accurate method of determining aluminum over a wide range of concentrations. This paper describes an accurate and fairly rapid polarographic method for determining aluminum based on the reduction of an aluminum-azo dye complex after removing titanium, and other interferences by cupferron precipitation, followed by electrolysis at a mercury cathode when necessary. The reduction takes place at — 0.44 volt versus the saturated calomel electrode in a solution buffered at pH 4.6 with acetate. The method is sensitive from 0.01 mg to 0.50 mg of aluminum per 50 ml, covering a range of 0.005 to 10.0 per cent aluminum.     

Formation of nematic liquid crystals of sterically stabilized layered double hydroxide platelets

Colloidal platelets of hydrotalcite, a layered double hydroxide, have been prepared by coprecipitation at pH 11-12 of magnesium nitrate and aluminum nitrate at two different magnesium to aluminum ratios. Changing the temperature and ionic strength during hydrothermal treatment, the platelets were tailored to different sizes and aspect ratios. Amino-modified polyisobutylene molecules were grafted onto the platelets following a convenient new route involving freeze-drying. Organic dispersions in toluene were prepared of the particles with the largest size and highest aspect ratio. The colloidal dispersions prepared in this way showed isotropic-nematic phase transitions above a limiting concentration in a matter of days. The number density at the transition and the width of the biphasic region were determined and compared to theory. The orientation of the platelets in nematic droplets (tactoids) and at the isotropic-nematic interface were analyzed by polarization microscopy. It was observed that sedimentation induces a nematic layer in samples that are below the limiting concentration for isotropic-nematic phase separation. No nematic phase was observed in the initial aqueous suspensions of the ungrafted particles.     

Practical, scalable, high-throughput approaches to eta3-pyranyl and eta3-pyridinyl organometallic enantiomeric scaffolds using the Achmatowicz reaction

A unified strategy for the high-throughput synthesis of multigram quantities of the eta(3)-oxopyranyl- and eta(3)-oxopyridinylmolybdenum complexes TpMo(CO)(2)(eta(3)-oxopyranyl) and TpMo(CO)(2)(eta(3)-oxopyridinyl) is described (Tp = hydridotrispyrazolylborato). The strategy uses the oxa- and aza-Achmatowicz reaction for the preparation of these organometallic enantiomeric scaffolds, in both racemic and high enantiopurity versions.     

Palladium/tetraphosphine catalyzed suzuki cross‐coupling of heteroarylboronic acids with aryl halides

cis,cis,cis‐1,2,3,4‐Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C₃H₅)]₂ efficiently catalyses the Suzuki reaction of heteroarylboronic acids with aryl bromides and also the coupling of arylboronic acids with heteroaryl bromides. The coupling of thiophene‐ or benzothiopheneboronic acids, furan‐ or benzofuranboronic acids and 3‐pyridineboronic acid with a variety of aryl bromides gave the corresponding coupling products in good yields. However, in most cases, better results in terms of ratio substrate/catalyst were obtained for the reverse reaction using heteroaryl bromides with arylboronic acids.