Controlling the atomic distribution in PtPd nanoparticles: thermal stability and reactivity during NO abatement.

In situ X-ray absorption spectroscopy and mass spectrometry measurements were employed to simultaneously probe the atom specific short range order and reactivity of Pd and PtPd nanoparticles towards NO decomposition at 300 °C. The nanoparticles were synthesized by a well controlled, eco-friendly wet chemical reduction of metal salts and later supported on activated carbon. Particularly for the bimetallic PtPd samples, distinct atomic arrangements were achieved using a seeding growth method, which allowed producing a random nanoalloy, or nanoparticles with Pt- or Pd-rich core. X-ray photoelectron spectroscopy, transmission electron microscopy, and X-ray diffraction provided additional insights on their electronic, morphological and long range order structural properties. The results revealed that the higher the thermal induced atomic migration observed within the nanoparticles during thermal treatments, the least were their reactivity for NO abatement.

Lithographically fabricated silicon microreactor for in situ characterization of heterogeneous catalysts­Enabling correlative characterization techniques.

We report on a new modular setup on a silicon-based microreactor designed for correlative spectroscopic, scattering, and analytic on-line gas investigations for in situ studies of heterogeneous catalysts. The silicon microreactor allows a combination of synchrotron radiation based techniques (e.g., X-ray diffraction and X-ray absorption spectroscopy) as well as infrared thermography and Raman spectroscopy. Catalytic performance can be determined simultaneously by on-line product analysis using mass spectrometry. We present the design of the reactor, the experimental setup, and as a first example for an in situ study, the catalytic partial oxidation of methane showing the applicability of this reactor for in situ studies.

The SAMBA quick-EXAFS monochromator: XAS with edge jumping.

Results and performances of the QEXAFS double monochromator of the SAMBA beamline (Synchrotron SOLEIL) are presented. The device is capable of speeds of up to 40 Hz, while giving the user the possibility to choose the amplitude of the scan from 0.1° to 4° in a few seconds. The device is composed of two independent units and it is possible to perform scans alternating between two different crystals, literally jumping from low (4 keV) to high (37 keV) energies.

The effect of information on listeners' attitudes toward speakers with voice or resonance disorders.

This study investigated university students' attitudes toward women with voice or resonance disorders and whether providing listeners with information about those disorders affected their attitudes towards the women. Eighty students listened to speech samples of 9 women: 3 with normal voice/resonance, 3 with moderate hoarseness/breathiness, and 3 with moderate hypernasality and nasal emission. Before listening to the speech samples, 40 students read two pages of information about the disorders, and 40 read two pages of neutral information. Attitudes were measured with 24 semantic differential scales. Results indicated that listeners perceived speakers with voice/resonance disorders more negatively than speakers without disorders. The attitudes of listeners who read voice and resonance information did not differ from those of listeners who read neutral information.

The influence of dentures on nasalance values in speech.

OBJECTIVE: The purpose of this study was to investigate the effects of maxillary dentures on nasalance values in normal elderly individuals. DESIGN: A three-factor within-subjects experimental design was employed to analyze the nasalance scores obtained. PARTICIPANTS: Twenty English-speaking women aged 61 to 81 years, who wore complete maxillary dentures, participated in the study. INTERVENTION: A Nasometer was used to collect nasalance data. Participants read three standard passages aloud, three times each, in two conditions: with and without their maxillary dentures. RESULTS: Results revealed that nasalance values were significantly lower with the maxillary dentures removed (p<.01), although the difference in nasalance between the two denture conditions averaged no more than 2%. Nasalance scores obtained both with and without maxillary dentures fell within one standard deviation of the mean for a reference group of comparably aged English-speaking women. CONCLUSIONS: The results suggest that the existing collection of normal reference data for nasalance may be safely used for elderly individuals regardless of their status with respect to natural or prosthetic maxillary dentition.

Laryngeal airway resistance in teachers with vocal fatigue: a preliminary study.

A noninvasive pressure-flow technique was used to compare laryngeal airway resistances in nine female classroom teachers with symptoms of vocal fatigue and seven teachers without symptoms of vocal fatigue. Data were collected two times per day on the Monday, Wednesday, and Friday of a typical work-week. No significant between-group differences were found, but two within-group differences were notable. Airflow in the fatigued subjects decreased across the sampling period (p = .0009). In the controls, air pressure increased across the sampling period (p = .021). These findings suggest that both groups may have reacted to vocal demands during the week by employing two different strategies to maintain habitual laryngeal airway resistance: laryngeal adjustments alone or laryngeal adjustments plus increased respiratory drive. The first strategy, employed by the fatigued subjects, may have been less efficient, thereby provoking conditions associated with their vocal fatigue.

Dyspnea following experimentally induced increased nasal airway resistance.

Nasal resistance (NRZ) values for healthy adults range from 1.0 to 3.5 cm H2O/L/sec. Some oral breathing tends to occur at values above 3.5. The purpose of the present study was to determine at what level of NRZ individuals sense that nasal breathing is difficult. A diaphragm was used to add four different resistance loads in random to 15 adult subjects. These loads were 5,8, and 15 cm H2O/L/sec and a value 40% above the individual's normal NRZ. Loads were added under four conditions: normal breathing, fixed flow rate, fixed breathing rate, and fixed flow and breathing rate. The pressure-flow technique was used to measure NRZ under all conditions. The study revealed that the sensation of breathing difficulty occurred at a median resistance of 5 cm H2O/L/sec and, as subjects were constrained to maintain fixed flow and breathing rates, the magnitude of RZ, at which the sensation of dyspnea was noted, decreased. The values observed in this study support previous findings suggesting that individuals switch to some oral breathing to maintain an adequate level of upper airway resistance at values between 3.5 and 4.5 cm H2O/L/sec. The findings also show that individuals attempt to minimize increases in airway resistance by modifying breathing behaviors.

An appliance based approach to the management of palatopharyngeal incompetency: a clinical pilot project.

The palatal lift appliance has been described in the dental literature for more than 30 years, yet its efficacy remains controversial in the management of palatopharyngeal incompetency during speech. A pilot project was undertaken to develop a clinical research protocol. In the pilot project, 32 patients had palatopharyngeal incompetency managed with a palatal lift appliance. The results of the treatment were that 21 of the 32 patients experienced reduction programs but, of these, seven still required surgery. Before firm conclusions on the use of the palatal lift appliance can be made, objective, measurable assessment of speech through well-designed clinical protocols is required.

Controlling changes in vocal tract resistance.

There is some evidence that speech aerodynamics follows the rules of a regulating system. The purpose of the present study was to assess how the speech system manages perturbations that produce "errors" within the system. Three experimental approaches were used to evaluate the physiological responses to an imposed change in airway resistance. The first involved subjects with varying degrees of velopharyngeal inadequacy. The second and third approaches involved noncleft subjects whose airway was perturbed by bleed valves and bite blocks during consonant productions. The pressure-flow technique was used to measure aerodynamic variables associated with the production of test consonants. The results of this study provide additional evidence that the speech system actively responds to perturbations in ways that tend to minimize a change in consonant speech pressures. The degree of success in stabilizing pressures appears to reflect the capability of the system to use whatever articulatory and respiratory responses are available.

Respiratory response to a decrease in velopharyngeal resistance.

Individuals with congenital velopharyngeal impairment generally maintain adequate levels of intraoral pressures during consonant production by increasing respiratory effort. The purpose of the present study was to determine if normal individuals respond to a decrease in velopharyngeal resistance in a similar way. The velar mechanism was perturbed by having subjects voluntarily lower the soft palate during a series of words involving plosive consonants. The pressure-flow technique was used to measure oral pressures, calculate velopharyngeal orifice resistance, and estimate velopharyngeal orifice area. Inductive plethysmography was used to measure breathing volumes associated with the words. The data indicate that, in most instances, intraoral pressure remained at appropriate levels (greater than 3.0 cm H2O) after velar lowering. Speech breathing volume did not change during inspiration, but increased during speech expiration when the velopharyngeal port was open. The difference was statistically significant (p less than 0.01). Duration of the utterance did not change across conditions. A mechanical model was then used to determine how intraoral pressure would be affected by simulating the same conditions in a passive system. The modeling data revealed that pressure would drop threefold. It was concluded that increased respiratory volumes tend to stabilize intraoral pressure when vocal tract resistance is experimentally reduced.

Characteristics of speech breathing in young women.

Chest wall kinematic records were obtained from 10 healthy young women in the upright, seated position during resting breathing, conversation, and reading aloud. Breathing frequency, lung volume levels relative to resting end-expiratory level, and relative volume displacements of the rib cage and abdomen were measured. Compared to conversation, group results for reading revealed three differences: an increase in syllables spoken per breath, an absence of filled pauses, and a slight upward shift in end-inspiratory and end-expiratory lung volume levels. Compared to resting breathing, group results for speech revealed four differences: a background chest wall configuration characterized by a relatively larger rib cage and smaller abdomen, slight increases in breathing frequency and in lung volume expenditure, and a slight decrease in rib cage contribution to lung volume displacement. The physical characteristic most strongly associated with rib cage contribution to lung volume displacement in resting breathing was height (r = .76). In comparing the relationship between the same respiratory behavior during resting breathing and speech, a correlation of .83 was obtained for rib cage contribution to volume displacement in the two conditions and of .60 for end-inspiratory volume level in the two conditions. Somewhat weaker positive correlations were obtained for lung volume expenditure and for breathing frequency in the two conditions. Comparison of the present findings for women to those recently reported for comparable men (Hoit & Hixon, 1987) revealed no remarkable differences in speech breathing characteristics. Results suggest that certain physical characteristics and task variables may have greater functional importance than gender in determining normative speech breathing behaviors.