| 11. |
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| 12. |
- Szabo, Annika, 1972-, et al.
(författare)
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A voice accumulator device : evaluation based on studio and field recordings.
- 2001
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Ingår i: Logopedics, Phoniatrics, Vocology. - : Informa UK Limited. - 1401-5439 .- 1651-2022. ; 26:3, s. 102-117
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Tidskriftsartikel (refereegranskat)abstract
- A voice accumulator is a portable device for long-term measurements of voice use in natural conditions. A contact microphone attached to the front part of the neck registers vocal fold vibrations. The purposes of the present study were: 1) to evaluate the voice accumulator's two measuring programs optimized for registration of fundamental frequency (F0) and phonation time, respectively; and 2) to test the voice accumulator for field recordings. Four healthy subjects were recorded in a sound-proof booth simultaneously with one contact microphone into a voice accumulator and one contact microphone into a computer. In terms of F0 and phonation time, the results showed that correlations between the voice accumulator's two measuring programs and a signal-processing program were high (r > or = 0.85) for all subjects but one. The inter-subject variability was large. A prerequisite for reliable vocal fold vibration detection by the voice accumulator was a careful placement and a firm attachment of the contact microphone on the neck. Four subjects were recorded with the voice accumulator during a working day. It was concluded that the voice accumulator is an overall good instrument for measurements of F0 and phonation time, and thus is useful for both clinical work and research.
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Södersten, M., et al.
(författare)
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Vocal behavior and vocal loading factors for preschool teachers at work studied with binaural DAT recordings
- 2002
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Ingår i: Journal of Voice. - : Mosby. - 0892-1997 .- 1873-4588. ; 16:3, s. 356-371
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Tidskriftsartikel (refereegranskat)abstract
- Preschool teachers are at risk for developing voice problems such as vocal fatigue and vocal nodules. The purpose of this report was to study preschool teachers' voice use during work. Ten healthy female preschool teachers working at daycare centers (DCC) served as subjects. A binaural recording technique was used. Two microphones were placed on both sides of the subject's head, at equal distance from the mouth, and a portable DAT recorder was attached to the subject's waist. Recordings were made of a standard reading passage before work (baseline) and of spontaneous speech during work. The recording technique allowed separate analyses of the level of the background noise, and of the subjects' voice sound pressure level, mean fundamental frequency, and total phonation time. Among the results, mean background noise level for the ten DCCs was 76.1 dBA (range 73.0-78.2), which is more than 20 dB higher than what is recommended where speech communication is important (50-55 dBA). The subjects spoke on an average of 9.1 dB louder (p < 0.0001), and with higher mean fundamental frequency (247 Hz) during work as compared to the baseline (202 Hz) (p < 0.0001). Mean phonation time for the group was 17%, which was considered high. It was concluded that preschool teachers do have a highly vocally demanding profession. Important steps to reduce the vocal loading for this occupation would be to decrease the background noise levels and include pauses so that preschool teachers can rest their voices.
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| 17. |
- Vallet, V., et al.
(författare)
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Solvent effects on uranium(VI) fluoride and hydroxide complexes studied by EXAFS and quantum chemistry
- 2001
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 40:14, s. 3516-3525
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Tidskriftsartikel (refereegranskat)abstract
- The structures of the complexes UO2Fn(H2O)(5-n)(2-n), n = 3-5, have been studied by EXAFS. All have pentagonal bipyramid geometry with U-F of and U-H2O distances equal to 2.26 and 2.48 Angstrom, respectively. On the other hand the complex UO2(OH)(4)(2-) has a square bipyramid geometry both in the solid state and in solution. The structures of hydroxide and fluoride complexes have also been investigated with wave function based and DFT methods in order to explore the possible reasons for the observed structural differences. These studies include models that describe the solvent by using a discrete second coordination sphere, a model with a spherical, or shape-adapted cavity in a conductor-like polarizable continuum medium (CPCM), or a combination of the two. Solvent effects were shown to give the main contribution to the observed structure variations between the uranium(VI) tetrahydroxide and the tetrafluoride complexes. Without a solvent model both UO2(OH)(4)(H2O)(2-) and UO2F4(H2O)(2-) have the same square bipyramid geometry, with the water molecule located at a distance of more than 4 Angstrom from uranium and with a charge distribution that is very near identical in the two complexes. Of the models tested, only the CPCM ones are able to describe the experimentally observed square and pentagonal bipyramid geometry in the tetrahydroxide and tetrafluoride complexes. The geometry and the relative energy of different isomers of UO2F3(H2O)(2)(-) are very similar, indicating that they are present in comparable amounts in solution. All calculated bond distances are in good agreement with the experimental observations, provided that a proper model of the solvent is used.
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| 18. |
- Vallet, V., et al.
(författare)
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The mechanism for water exchange in UO2(H2O)(5) (2+) and UO2(oxalate)(2)(H2O) (2-), as studied by quantum chemical methods
- 2001
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 123:48, s. 11999-12008
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms for the exchange of water between [UO2(H2O)(5)](2+), [UO2(oxalate)(2)(H2O)](2-), and water solvent along dissociative (D), associative (A) and interchange (1) pathways have been investigated with quantum chemical methods. The choice of exchange mechanism is based on the computed activation energy and the geometry of the identified transition states and intermediates. These quantities were calculated both in the gas phase and with a polarizable continuum model for the solvent. There is a significant and predictable difference between the activation energy of the gas phase and solvent models: the energy barrier for the D-mechanism increases in the solvent as compared to the gas phase, while it decreases for the A- and I-mechanisms. The calculated activation energy, AW, for the water exchange in [UO2(H2O)(5)](2+) is 74, 19, and 21 kJ/mol, respectively, for the D-, A-, and I-mechanisms in the solvent, as compared to the experimental value DeltaH(double dagger) = 26 +/- 1 kJ/mol. This indicates that the D-mechanism for this system can be ruled out. The energy barrier between the intermediates and the transition states is small, indicating a lifetime for the intermediate approximate to 10(-10) s, making it very difficult to distinguish between the A- and I-mechanisms experimentally. There is no direct experimental information on the rate and mechanism of water exchange in [UO2(oxalate)(2)(H2O)](2-)containing two bidentate oxalate ions. The activation energy and the geometry of transition states and intermediates along the D-, A-, and I-pathways were calculated both in the gas phase and in a water solvent model, using a single-point MP2 calculation with the gas phase geometry. The activation energy, AW, in the solvent for the D-, A-, and I-mechanisms is 56, 12, and 53 kJ/mol, respectively. This indicates that the water exchange follows an associative reaction mechanism. The geometry of the A- and I-transition states for both [UO2(H2O)(5)](2+) and [UO2(oxalate)(2)(H2O)](2-) indicates that the entering/leaving water molecules are located outside the plane formed by the spectator ligands.
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