Effect Of Surface Hydration Research Articles

A Multiparametric Acoustic and Self-Perceptual Measure of Laryngeal Hydrations in Speech-Language Pathologists: A Preliminary Longitudinal Investigation

PurposeSpeech-language pathologists (SLPs) work with individuals with communication disorders. Their work can strain their voice, resulting in dysphonia, adversely affecting their career and quality of life. Laryngeal hydration can prevent vocal damage and improve vocal performance in SLPs. However, there is limited research on the effects of laryngeal hydration in SLPs using longitudinal studies. Hence, the present study aims to assess the longitudinal impact of laryngeal hydration in SLPs using multiparametric acoustic and self-perceptual measures. MethodThe research method lasted for six consecutive days, with each day lasting 2-3 hours for each participant. Ten SLPs, aged 18-30 years, were recruited. On alternate days, laryngeal hydration treatment (Systemic, surface, and combined hydration) was given while participants performed vocal loading tasks. Pre- and post-recordings of the Acoustic Voice Quality Index (AVQI) and its consistent parameters (CPPs, HNR, shimmer%, shimmer local, LTAS slope, LTAS Tilt) and self-perceptual measures [Perceived Phonatory Effort (PPE), Perceived Vocal Tiredness (PVT)] were taken. Kruskal-Wallis Test and the Wilcoxon Signed Rank Test were used to assess vocal changes in SLPs with laryngeal hydration. ResultsNo significant differences in overall AVQI scores were found between pre and post-tests for all types of laryngeal hydration treatment. However, there was a significant increase in CPPs and the LTAS slope for combined hydration and a decrease in HNR with an increase in shimmer local for systemic hydration in the post-test compared to the pre-test. Only systemic hydration in the post-test showed a rise in PPE and PVT compared to the pre-test, compared to surface and combined hydration. ConclusionVoice outcome measures of the present study demonstrated the immediate beneficial effects of surface hydration and combined hydration in SLPs by preserving voice quality during vocal loading. Systemic hydration had less of an immediate impact on voice quality. This study suggests empirical evidence for laryngeal hydration, which can enhance vocal performance and preserve voice quality in SLPs.

Why the Photochemical Reaction of Phenol Becomes Ultrafast at the Air-Water Interface: The Effect of Surface Hydration.

Photochemical reactions at the air-water interface can show remarkably different rates from those in bulk water. The present study elucidates the reaction mechanism of phenol characteristic at the air-water interface by the combination of molecular dynamics simulation and quantum chemical calculations of the excited states. We found that incomplete hydrogen bonding to phenol at the air-water interface affects excited states associated with the conical intersection and significantly reduces the reaction barrier, resulting in the distinctively facilitated rate in comparison with the bulk phase. The present study indicates that the reaction dynamics can be substantially different at the interfaces in general, reflecting the difference in the stabilization energy of the electronic states in markedly different solvation at the interface.

The effects of surface hydration on capillary adhesion under nanoscale confinement.

Nanoscale phenomena such as surface hydration and the molecular layering of liquids under strong nanoscale confinement play a critical role in liquid-mediated surface adhesion that is not accounted for by available models, which assume a uniform liquid density with or without considering surface forces and associated disjoining pressure effects. This work introduces an alternative theoretical description that via the potential of mean force (PMF) considers the strong spatial variation of the liquid number density under nanoscale confinement. This alternative description based on the PMF predicts a dual effect of surface hydration by producing: (i) strong spatial oscillations of the local liquid density and pressure and, more importantly, (ii) a configuration-dependent liquid-solid surface energy under nanoscale confinement. Theoretical analysis and molecular dynamics simulations for the case of an axisymmetric water bridge with nanoscale heights show that the latter hydration effect is critical for the accurate prediction of the surface energy and adhesion forces when a small volume of liquid is nanoscopically confined by two surfaces approaching contact.

Model improvement for super-Nernstian pH sensors: the effect of surface hydration

The maximum sensitivity of pH sensors is given by the Nernst equation, and its theoretical value is 59.2 mV pH−1. However, countless sensors developed and reported in the literature have their sensitivity higher than the Nernstian limit. These are called super-Nernstian sensors. To understand the causes of this behavior, the sensitivity of polyaniline thin films was studied by evaluation of an important parameter: the hydration of the film’s surface. Sensitivities were measured before and after varied heat treatments, and the sensor's parameters were associated with the amount of water lost in the process. Polyaniline thin films were fabricated by galvanostatic electrodeposition in aqueous solution, and their sensitivity was measured before and after heating of the samples. An endothermic process, typical of evaporation, was revealed by the analysis of mass loss during the heating process. A decrease in the sensitivity of the films was observed after heating process. For comparison, polyaniline thin films were also fabricated by spin coating, in the absence of water, and their sensitivity proved to be smaller than for the galvanostatically fabricated ones and it did not change significantly after the heating processes. The results indicated that the Nernst model can be adjusted using a parameter ( $$1/r$$ ) related to the hydration of the surface of the sample, which directly affects the sensitivity of the thin films. The lowest reachable $$1/r$$ value for samples containing no water is approximately 0.9. The parameter also describes the upper limits for the sensitivity of super-Nernstian sensors.

Quantifying the auto-oscillation complexity following water spraying with interest for phonation.

Human voiced sound production or phonation is the result of a fluid-structure instability in the larynx leading to vocal folds auto-oscillation. In this paper, the effect of surface hydration following water spraying (0 up to 5ml) on an ongoing auto-oscillation is studied experimentally using different mechanical deformable vocal folds replicas. The complexity of the oscillation is quantified on the upstream pressure by a phase space recurrence and complexity analysis. It is shown that: (1) the ratio of the degree of determinism to the recurrence rate of the phase space states γ and (2) estimated correlation dimension D_{2} are suitable parameters to grasp the effect of hydration on the oscillation pattern. The oscillation regime after hydration can either remain deterministic or approach a chaotic regime depending on initial conditions prior to water spraying, such as elasticity, glottal aperture, as well as oscillation complexity.

Effects of surface hydration on the electron injection rate from graphene to anatase and rutile TiO2 surfaces

The effect of hydration of anatase (0 0 1), and rutile (0 0 1), (1 0 1) and (1 1 0) surfaces of TiO2 on the rate of electron capture from an adsorbed graphene sheet is elucidated by means of computation at a level of tight-binding density functional theory. Initially, the clean surfaces are allowed to interact with bulk water. Following an equilibration period, the first solvation shell is exposed to vacuum at 300 K for a sufficiently long period of time to allow any weakly bound water molecules to evaporate or be displaced from the surface. The resultant hydroxylated and originally clean surfaces are used for studying the interaction with a graphene sheet. Comparison of the calculated surface-graphene interaction energies and electron transfer probabilities of a cold electron to clean and hydroxylated surfaces shows that the water-sourced OH layer of these surfaces acts as an insulator in interfacial charge transport of the cold electron.

Self-perception of surface hydration effect on teachers’ voice quality: an intervention study

ABSTRACT Objective: to assess the effects of surface hydration on vocal quality according to teachers’ self-perception. Methods: an examiner-blinded pre-test and post-test intervention study carried out with a single group of 27 teachers. Sociodemographic characteristics and work questionnaire, Screening Index for Voice Disorder, Vocal Severity Rating Scale, Expected Effects Pre-intervention, Perceived Effects Post-intervention and Post-intervention Perception instruments, were applied. The intervention lasted 4 weeks and consisted of 5 minutes of nebulization with saline solution (sodium chloride 0.9%), after 10 minutes of mouth dehydration, prior to teaching. Results: screening Index for Voice Disorder scores demonstrated a statistically significant reduction (p=0.001). Frequency of voice disorders in the Vocal Severity Rating Scale was reduced without a statistical significance (p= 0.172). Expected Effects, Pre-intervention, and Perceived Effects, Post-intervention, showed improvement in vocal quality (40.7%), vocal comfort (40.7%) and vocal folds hydration (37%). Post-intervention perception form showed moderate improvement of the symptoms (59.3%), cleared voice (55.6%) and ease speaking (48.1%) as well as intense belief in the intervention (74.1%) and intense compliance to the intervention (74.1%). Conclusion: surface hydration with saline solution promoted self-perceived improvement in vocal quality.

Effect of Surface Hydration on Antifouling Properties of Mixed Charged Polymers.

Interfacial water structure on a polymer surface in water (or surface hydration) is related to the antifouling activity of the polymer. Zwitterionic polymer materials exhibit excellent antifouling activity due to their strong surface hydration. It was proposed to replace zwitterionic polymers using mixed charged polymers because it is much easier to prepare mixed charged polymer samples with much lower costs. In this study, using sum frequency generation (SFG) vibrational spectroscopy, we investigated interfacial water structures on mixed charged polymer surfaces in water and how such structures change while being exposed to salt solutions and protein solutions. The 1:1 mixed charged polymer exhibits excellent antifouling property whereas other mixed charged polymers with different ratios of the positive/negative charges do not. It was found that on the 1:1 mixed charged polymer surface, SFG water signal is dominated by the contribution of the strongly hydrogen bonded water molecules, indicating strong hydration of the polymer surface. The responses of the 1:1 mixed charged polymer surface to salt solutions are similar to those of zwitterionic polymers. Interestingly, exposure to high concentrations of salt solutions leads to stronger hydration of the 1:1 mixed charged polymer surface after replacing the salt solution with water. Protein molecules do not substantially perturb the interfacial water structure on the 1:1 mixed charged polymer surface and do not adsorb to the surface, showing that this mixed charged polymer is an excellent antifouling material.

Effect of surface hydration on the photocatalytic activity of oxide catalysts in the CO oxidation

The effect of the state of hydrated surface of the bulk oxide photocatalysts, TiO2, CeO2, and ZnO on the rate of UV-induced oxidation of CO with atmospheric oxygen was studied. The activity of dehydroxylated catalyst samples evacuated at temperatures of >350 °C toward CO photooxidation decreases in the series CeO2 > ZnO ≈ TiO2, while that of partially hydrated samples after pretreatment at 20 °C changes in the order TiO2 > ZnO ≥ CeO2 ≈ 0. According to the results, the difference in the photocatalytic activity toward CO oxidation on the dehydrated ZnO, TiO2, and CeO2 catalysts is attributable to different concentrations of oxygen vacancies, which are formed more readily after high-temperature treatment on ZnO and CeO2 and thus promote higher rate of CO photooxidation. Using a new technique for recording transmittance IR spectra, it was found that photoirradiation in the presence of adsorbed water and O2 gives peroxides and hydroperoxides, with their concentrations decreasing in the series TiO2 >> ZnO >> CeO2. Most likely, these species are active intermediates of CO photooxidation with oxygen in the presence of adsorbed water. The hydrophobization effect was detected upon TiO2 modification with zinc, resulting in removal of surface acid sites capable of adsorbing water. The TiO2 modification with zinc increases the activity of CO photooxidation with respect to the oxidation catalyzed by samples pretreated at low temperatures (20—60 °C).

Electrochemical Simultaneous Sensing of Melatonin, Dopamine and Acetaminophen at Platinum Doped and Decorated Alpha Iron Oxide

AbstractSimultaneous sensing of dopamine (DA), acetaminophen (AP) and melatonin (MEL) was made by electrochemical method as the drugs melatonin and acetaminophen interact with dopamine in brain to induce neuro disorders. The glassy carbon electrode surface was modified with un‐doped α‐ Fe2O3, platinum doped Fe2O3 (dPtFe2O3), Pt decorated Fe2O3 (sPtFe2O3) and doped and decorated Fe2O3 (sdPtFe2O3) nano particles that are synthesized by co‐precipitation method in presence of polyethylene glycol for the first time. These particles were characterized using Ultra‐Violet Visible (UV‐Vis), scanning electron microscopy (SEM), X‐ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA) and electrochemical techniques. The sdPtFe2O3 showed the highest catalytic activity than the dPtFe2O3, sPtFe2O3 and un‐doped α‐ Fe2O3 with well separated voltammetric peaks for DA and AP in presence of MEL. This is attributed to higher surface hydration effects of the sdPtFe2O3, dPtFe2O3 and sPtFe2O3 than the un‐doped Fe2O3 which plays a vital role in enhancing the melatonin sensing in presence of dopamine and acetaminophen. Linear ranges and lowest detection limits for all three analytes were increased by 10 times for the sdPtFe2O3 compared to other Fe2O3 modified electrodes. The sensor is validated using commercially available pharmaceutical drugs used in therapeutics.

The Effect of Surface Hydration on Teachers' Voice Quality: An Intervention Study

This study aimed to investigate the effects of surface hydration on teachers' voice quality. This is an examiner-blinded, pretest and posttest intervention study with a single group of subjects. Subjects were 27 teachers from a public-sector state school in Salvador, Bahia, Brazil. Pre- and post-intervention voice recordings were obtained. Voice samples collected underwent computerized acoustic analysis (VoxMetria) and perceptual analysis via the Consensus Auditory-Perceptual Evaluation of Voice. Intervention was conducted daily before teaching for a 4-week period, consisting of 5 minutes of nebulization with saline solution (NaCl 0.9%), after 10 minutes of dehydration breathing through the mouth. A reduction in the overall level of voice alteration was observed in the Consensus Auditory-Perceptual Evaluation of Voice, but with no statistical significance. The following were observed: an increase in the mean fundamental frequency of the vowel /a:/ (P = 0.036); a statistically significant reduction in the minimum intensity of connected speech (P = 0.028), in the median intensity of connected speech (P = 0.014), and in the maximum intensity of connected speech (P = 0.007). There was also a statistically significant reduction in the minimum (P = 0.001) and mean intensities of spontaneous speech (P = 0.011). Surface hydration with saline solution led to an improvement in teachers' voice quality.

Effect of Surface Hydration of Mg Rare Earth Mixed Oxides on Basicity and Activity for Aldol Condensation

Effect of Surface Hydration of Mg Rare Earth Mixed Oxides on Basicity and Activity for Aldol Condensation

Nature of β-TaON surfaces at ambient conditions

Abstract TaON has been recently identified as a promising water-splitting photocatalyst. Here we present the results of our detailed computational study to understand the exposed surfaces of β -TaON at ambient conditions. By employing periodic density functional theory, structures and electronic properties of all the low index native surfaces of β -TaON were studied. Nature of the β -TaON surfaces at ambient moist conditions was investigated using the ab initio thermodynamics approach. Based on the surface energies computed as a function of temperature ( T ) and pressure, we obtain the equilibrium shape of the β -TaON single crystal by the Wulff construction and study the exposure of these surfaces as a function of T at moist conditions. The effects of surface hydration and T on the exposure of the low-index surfaces are discussed. This study presents surface models relevant for studying catalytic reactions using β -TaON. Surface reactivity of the most stable surface of TaON is then analyzed.

Structure–activity relationships on metal-oxides: alcohol dehydration

The Lewis-acid catalyzed dehydration of simple alcohols on TiO2, ZrO2 and γ-Al2O3 oxide-catalysts has been investigated by combining ab initio theoretical calculations with temperature programmed desorption (TPD) experiments. Both theoretical and experimental results demonstrate that γ-Al2O3 is more active in catalyzing the dehydration reactions than either TiO2 or ZrO2. The dehydration reaction occurs through an E2-elimination mechanism involving either surface O and/or OH groups of the oxides. Based on relationships between the dehydration barriers and key properties of the alcohols and the oxides, a dehydration model was developed that is able to screen the dehydration performance of various alcohols on different metal oxides and provide predictions that were in good agreement with the experimental dehydration barriers. The model accounts for the effect of surface hydration and the existence of surface OH-groups. The basicity of the surface oxygens is shown to be important in eliminating beta hydrogens of the alcohols. This work highlights the importance of surface OH-groups as active centers for the elimination of beta hydrogens of alcohols in Lewis-acid catalyzed dehydration reactions, a result different from the conventional view that surface OH-groups are associated with Bronsted acidity. Most importantly, a novel methodology is introduced that develops structure–activity relationships on oxides for the conversion of biomass derived molecules to chemicals.

The importance of surface hydration and particle shape on the rheological property of silica-based suspensions

Two types of ball milling methods, wet planetary ball milling and dry tumbling ball milling, were used to grind fused silica powders for the preparation of silica-based suspensions in this experiment. The effect of surface hydration and particle shape caused by the two milling methods on the slurry rheology was investigated. The results showed that, with similar particle size distribution, the viscosity of the suspensions prepared from the powders milled by wet ball milling ranged from 275mPas to 311mPas within 20min and the suspension exhibited a continuous shear thickening behaviour whereas the viscosity of the suspensions prepared from the powders milled by dry ball milling ranged from 69mPas to 74mPas and the suspension exhibited a shear thinning behaviour first, and then exhibited a slightly shear thickening behaviour. The reasons were attributed to the differences in surface hydration and particle shape. It was postulated that the two factors affected the slurry rheology through the modification of particle interactions during the flow of high concentration suspensions.

Surface Hydration Amplifies Single-Well Protein Atom Diffusion Propagating into the Macromolecular Core

The effect of surface hydration water on internal protein motion is of fundamental interest in molecular biophysics. Here, by decomposing the picosecond to nanosecond atomic motion in molecular dynamics simulations of lysozyme at different hydration levels into three components--localized single-well diffusion, methyl group rotation, and nonmethyl jumps--we show that the effect of surface hydration is mainly to increase the volume of the localized single-well diffusion. These diffusive motions are coupled in such a way that the hydration effect propagates from the protein surface into the dry core.

The relationship between different spectral forms of the protochlorophyllide oxidoreductase complex and the structural organisation of prolamellar bodies isolated from Zea mays

Incubation of prolamellar bodies (PLB) in high-salt media leads to changes in PLB structure and properties of their protochlorophyllide oxidoreductase-protochlorophyllide (POR-PChlide) complex. The paracrystalline organisation typical of PLB is disrupted and NADPH dissociates from photoconvertible POR-PChlide, with absorption maxima at 640 and 650 nm (POR-PChlide (640/650)), and a non-photoconvertible form, with absorption maxima at 635 nm (POR-PChlide (635)), is formed. These effects are strongly dependent on the valence of the cation of the perturbing salt, indicating that they involve surface double layers effects. They are also influenced by the nature of the anion and by high concentrations of non-electrolytes, suggesting the involvement of surface hydration effects. The structural changes are largely, if not entirely, independent of the presence of excess NADPH. Changes to the POR-PChlide complex, however, are strongly inhibited by excess NADPH suggesting that the two sets of changes may not be causally linked. As long as the disruption is not too great, the structural changes seen on incubation of PLB in high salt media lacking excess NADPH are reversed on removal of the high salt perturbation. This reversal is independent of the presence or absence of added NADPH. Reformation of photoconvertible POR-PChlide, however, requires the presence of NADPH. The reformation of paracrystalline PLB in the absence of NADPH strongly indicates that preservation of PLB structure, in isolated PLB preparations at least, is independent of the presence or absence of POR-PChlide (650).

Adsorption of phenanthrene on Na-montmorillonite: A model study

The role of clay minerals in the fate of polycyclic aromatic hydrocarbons (PAHs) in soil still remains an unresolved and controversial issue. Recent experimental studies report on PAH sorption capacity of clay minerals, which is either much smaller than or comparable to that of soil organic matter with water either inhibiting or not inhibiting PAH sorption. We studied adsorption of phenanthrene – a prominent PAH representative – on Na-montmorillonite – a common member of the smectite group of clay minerals and often dominating component of soil inorganic matter – by means of molecular simulations incorporating free energy calculations. The study also included the effect of surface hydration on sorption. Phenanthrene adsorption site featured by Na +− π bonding was identified as the most favorable one on the dehydrated montmorillonite surface with other inner-sphere adsorption sites being less favorable by 23–32 kJ/mol and the desorption state being less favorable by 74 kJ/mol on the free energy scale. Upon montmorillonite hydration by a water film with a thickness of ~ 1 nm, however, phenanthrene desorption from the montmorillonite surface to the water–air interface becomes more favorable than phenanthrene direct adsorption. Our results support, therefore, experimental studies suggesting that PAHs adsorption on clays predominates in the dry soils but is negligible in the presence of water. Still, a consideration of higher phenanthrene surface coverages (to account for possible aggregation effect) or other exchangeable cations (to account for possible stronger cation − π bonding) in the future model studies may provide additional arguments pro or contra of this suggestion.

Mechanical properties of silicate glasses as a function of composition

Bulk production of silicate glasses is based around a narrow range of soda–lime–silica compositions and as a result any variation in mechanical properties with composition is normally considered to be of little interest. However, studies by a range of authors over the last 50 years or so have demonstrated some intriguing variations of properties such as toughness, brittleness and, more controversially, strength with composition. We have produced several series of alkali-mixed alkaline earth-silicate glasses and are assessing the variation of their mechanical properties with composition using both conventional indentation and nanoindentation. The nanoindentation studies are also being used to assess the effects of surface hydration on the near surface mechanical properties of these glasses. This presentation reviews the results we have obtained to date and attempts to draw out some wider conclusions concerning the compositional dependences of the mechanical properties of silicate glasses.

Forces between insulin microspheres and polymers surfaces for a dry powder inhaler

Here we demonstrate the use of a colloidal probe atomic force microscope (AFM) to compare the interactions between a model protein microsphere (insulin) and a set of common device polymers (polytetrafluoroethylene, polyethylene and polypropylene) with and without antistatic additive. For inhalation-based delivery devices the solid protein microspheres will interact with the device surfaces under ambient atmospheric conditions, and as such we studied the particle device interaction at a range of relative humidities. The results clearly discriminate between the five different polymer choices, and the impact of the antistatic additive. Although the mechanistic understanding is incomplete, it is evident that the polypropylene with antistatic additive gives consistent and relatively small interaction forces over the entire humidity range. The other polymer surfaces have humidity ranges where the pull-off forces are substantially greater. At 80% relative humidity, the insulin-polymer adhesion forces were similar for all the polymers probably due to the dominance of static charge mitigation and surface hydration effects. Overall, direct measurement of adhesion forces between pharmaceutical microspheres and container substrates can help direct rational choice of plastics/coatings for medical devices.