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41.
Oral breathing superficially dehydrates the airway lumen by decreasing the depth of the sol layer in humans and animals. Conversely, nasal breathing can increase the humidity of inspired air. We compared the effects of short-term oral and nasal breathing on Pth and perceived vocal effort in 20 female subjects randomly assigned to two groups: oral breathing (N = 10, age 21–32 years); nasal breathing (N = 10, age 20–36 years). We hypothesized that short-term oral breathing, but not nasal breathing, would increase Pth, and that subjects would perceive this change as an increase in vocal effort. Following 15 minutes of oral breathing, Pth increased at comfortable and low pitch (p < 0.01) with 6 of 10 subjects reporting increased vocal effort. Nasal breathing reduced Pth at all three pitches (p < 0.01), and 7 of 10 subjects reported decreased vocal effort. Over all subjects, 49% of the variance in treatment-induced change in Pth was accounted for by change in vocal effort (R = 0.70). We posit that obligatory oral breathing places healthy subjects at risk for symptoms of increased vocal effort. The facilitatory role of superficial hydration on vocal fold oscillation should be considered in biomechanical models of phonation and in the clinical prevention of laryngeal dryness.  相似文献   
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The RENiZn (RE = La, Tb), RE2Ni2Zn (RE = La, Ce, Tb) and La3Ni3Zn ternary compounds were synthesized by two methods: by heating in a resistance furnace evacuated quartz ampoules containing Al2O3‐crucibles with element pieces and by induction melting in sealed Ta crucibles with subsequent annealing at 400 °C. Scanning electron microscopy (SEM) coupled with energy dispersive X‐ray spectroscopy (EDXS) was used for examining microstructure and phase composition of some of the alloys. The crystal structures for all the investigated phases were solved or confirmed on single crystal data by applying the direct methods refined by a standard least square procedure: LaNiZn – str. type ZrNiAl, hexagonal, , hP9, a = 0.7285(1), c = 0.3938(1) nm, wR2 = 0.0534, 257 F2 values, 14 variables; a = 0.7044(1), c = 0.3782(1) nm, wR2 = 0.0447, 236 F2 values, 14 variables for TbNiZn; La2Ni2Zn – str. type Pr2Ni2Al, orthorhombic, Immm, oI10, a = 0.4381(1), b = 0.5459(1) c = 0.8605(2) nm, wR2 = 0.0824, 223 F2 values, 13 variables; a = 0.4365(1), b = 0.5430(1) c = 0.8279(2) nm, wR2 = 0.0635, 209 F2 values, 13 variables for Ce2Ni2Zn; a = 0.4209(1), b = 0.5366(1) c = 0.8165 (1) nm, wR2 = 0.0757, 200 F2 values, 13 variables for Tb2Ni2Zn; La3Ni3Zn – str. type Y3Co3Ga, orthorhombic, Cmcm, oS28, a = 0.4276(1), b = 1.0310(2) c = 1.3636(3) nm, wR2 = 0.0859, 579 F2 values, 26 variables. The structural peculiarities of these compounds and their relations are discussed.  相似文献   
44.
The dynamics and the associated heat transfer process of butane droplets evaporating in water are investigated experimentally. New data are presented for the instantaneous growth, rise velocity and the heat transfer coefficient. The behaviour of the bubble-droplet, from the initial to the final stages of evaporation, is divided into four regions and is described with reference to similarities with the behaviour of a spherical droplet, spheroidal bubble-droplet, large spheroidal bubble and spherical cap bubble. The equations which represent the results for the heat transfer coefficient are given.  相似文献   
45.
Sustained high notes, diminishing gradually from the loudest to the softest phonation within a maneuver called messa di voce, are examined in two contrasting professional tenor voices. Signals of the sound pressure level, electroglottograph, and mean esophageal pressure are recorded, and similar maneuvers by the same subjects are examined stroboscopically. The lyric voice is found to make a gradual diminuendo while maintaining nearly constant posture of the vocal tract together with a phase of complete closure in the glottal cycle. The robust voice, by contrast, passes abruptly from a production of high subglottal pressure and a high closed quotient to one of low pressure and incomplete closure, and the transition is marked by a sudden opening of the previously constricted laryngeal collar. It is proposed that the mode of soft voice production demonstrated by the robust voice be recognized as a distinct register of the singing voice.  相似文献   
46.
Amyloid fibril formation of proteins is of great concern in neurodegenerative disease and can be detrimental to the storage and stability of biologics. Recent evidence suggests that insulin fibril formation reduces the efficacy of type II diabetes management and may lead to several complications. To develop anti-amyloidogenic compounds of endogenous origin, we have utilized the hydrogen bond anchoring, π stacking ability of porphyrin, and investigated its role on the inhibition of insulin amyloid formation. We report that hydroxylation and metal removal from the heme moiety yields an excellent inhibitor of insulin fibril formation. Thioflavin T, tyrosine fluorescence, Circular Dichorism (CD) spectroscopy, Field emission scanning electron microscopy (FESEM) and molecular dynamics (MD) simulation studies suggest that hematoporphyrin (HP) having hydrogen bonding ability on both sides is a superior inhibitor compared to hemin and protoporphyrin (PP). Experiments with hen egg white lysozyme (HEWL) amyloid fibril formation also validated the efficacy of endogenous porphyrin based small molecules. Our results will help to decipher a general therapeutic strategy to counter amyloidogenesis.  相似文献   
47.
A specific and sensitive LC–MS/MS method using d3-glycopyrrolate as the internal standard (IS) was developed for the quantitative determination of glycopyrrolate (GLY) in human plasma over a concentration range of 4.00–2000 pg/ml. The GLY and IS were extracted using a solid-phase extraction cartridge, then eluted with 0.5% formic acid in 70:30 acetonitrile–water. The eluate was directly injected into an Agilent Pursuit 5PFP column for analysis using an isocratic mobile phase of 50:50 A:B at a flow-rate of 0.500 ml/min (A, 10 mm ammonium acetate in 1% formic acid; B, methanol). The MS detection was in positive mode by monitoring m/z 318.3 → 116.1 (GLY) and 321.3 → 119.1 (IS). The method validation showed the linearity of r2 ≥ 0.9960, intra-/inter-run precisions of ≤11.1% coefficient of variation and accuracies ranging from −2.5 to 12.8% relative error for all levels of quality control samples. This method was successfully employed to support a clinical study to compare absorption and bioavailability of GLY administered by a Magnair® eFlow nebulizer to a Seebri® Breezhaler® with/without a charcoal blockade of gastric absorption. By comparison with intravenous administration, respective bioavailabilities of ~15% for GLY/Magnair and ~22% for the Seebri Breezhaler were found. The bioanalytical reliability was also demonstrated by satisfactory incurred sample reanalysis performance.  相似文献   
48.
How salt ions affect solutes and the water beyond the solvation shell is not well understood. Molecular dynamics simulations of alkali-acetate solutions were analysed here in order to examine if, and how, different cations and solute concentrations affect the water structure and the interactions between water and acetates. The results revealed that water structure is perturbed to more than 1 nm away from the acetates and that this effect is more pronounced in physiological than in molar electrolyte concentrations. Analysis of simulations of a soluble protein revealed that the water orientation is perturbed to at least 1.5 nm from the protein structure. Furthermore, modifications to the orientation of water around carboxylate side chains were shown to depend on the local environment on the protein surface, and could extend to well over 1 nm, which may have an effect on protein dynamics during MD simulations in small water boxes.  相似文献   
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Abstract

At ALCOM's international symposium on 12 – 13 October, 1995, over 100 participants gathered in beautiful Cuyahoga Falls, Ohio, to discuss current developments in dynamics and defects in liquid crystals and to honour Professor Alfred Saupe on the occasion of his 70th birthday. ALCOM, the US National Science Foundation and Technology Center on Advanced liquid Crystalline Optical Materials, is a consortium of Kent State, Case Western Reserve and Akron Universities.  相似文献   
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