| 1. |
- Lehto, Laura, et al.
(författare)
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Comparison of two inverse filtering methods in parameterization of the glottal closing phase characteristics in different phonation types
- 2007
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Ingår i: Journal of Voice. - : Elsevier BV. - 0892-1997 .- 1873-4588. ; 21:2, s. 138-150
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Tidskriftsartikel (refereegranskat)abstract
- Inverse filtering (IF) is a common method used to estimate the source of voiced speech, the glottal flow. This investigation aims to compare two IF methods: one manual and the other semiautomatic. Glottal flows were estimated from speech pressure waveforms of six female and seven male subjects producing sustained vole /a/ in breathy, normal, and pressed phonation. The closing phase characteristics of the glottal pulse were parameterized using two time-based parameters: the closing quotient (C1Q) and the normalized amplitude quotient (NAQ). The information given by these two parameters indicates a strong correlation between the two IF methods. The results are encouraging in showing that the parameterization of the voice source in different speech sounds can be performed independently of the technique used for inverse filtering.
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| 2. |
- Toropainen, Tarja, et al.
(författare)
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Crystal structure changes of gamma-cyclodextrin after the SEDS process in supercritical carbon dioxide affect the dissolution rate of complexed budesonide
- 2007
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Ingår i: Pharmaceutical research. - : Springer Science and Business Media LLC. - 0724-8741 .- 1573-904X. ; 24:6, s. 1058-1066
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Tidskriftsartikel (refereegranskat)abstract
- Purpose. The present study describes the crystal structure changes of γ-cyclodextrin (γ-CD) during the solution enhanced dispersion by supercritical fluids (SEDS) process and its effect on dissolution behaviour of complexed budesonide. Materials and Methods. γ-CD solution (10 mg/ml in 50% ethanol) was pumped together with supercritical carbon dioxide through a coaxial nozzle with or without a model drug, budesonide (3.3 mg/ml). The processing conditions were 100 b and 40, 60 or 80°C. γ-CD powders were characterised before and after vacuum-drying (2-3 days at RT) with XRPD, SEM and NMR. Budesonide/γ-CD complexation was confirmed with DSC and XRPD. The dissolution behaviour of complexed budesonide was determined in aqueous solution (1% γ-CD, 37°C, 100 rpm). Results. During the SEDS process (100 b, 40 and 60°C), γ-CD and budesonide/γ-CD complexes crystallized in a tetragonal channel-type form. The vacuum-drying transformed crystalline γ-CD into amorphous form while the complexes underwent a tetragonal-to-hexagonal phase transition. The increase in the processing temperature decreased the crystallinity of γ-CD. At 80°C, amorphous γ-CD was obtained while the complexes crystallized in a hexagonal channel-type form. The dissolution behaviour of budesonide/γ-CD complexes was dependent on their crystal structure: the tetragonal form dissolved faster than the hexagonal form. Conclusions. The crystal structure of γ-CD and subsequently, the dissolution rate of complexed budesonide, can be modified with the processing conditions.
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| 3. |
- Toropainen, Tarja, et al.
(författare)
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Preparation of budesonide/gamma-cyclodextrin complexes in supercritical fluids with a novel SEDS method
- 2006
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Ingår i: Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0022-3549 .- 1520-6017. ; 95:10, s. 2235-2245
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to investigate if solid drug/cyclodextrin complexes could be produced in a single-step process with a solution enhanced dispersion by supercritical fluids (SEDS) method. Budesonide and gamma-cyclodextrin (CD) solutions (50% or 99.5% ethanol) were pumped from the same (conventional method) or separate (modified method) containers together with supercritical carbon dioxide through a coaxial nozzle into a particle formation chamber. The pressure was maintained at 100, 150 or 200 bar with a temperature of 40, 60 or 80 degrees C. SEDS-processed powders were characterised with HPLC, DSC and XRPD for budesonide content, complexation and crystallinity. The budesonide dissolution rate was determined in 1% gamma-CD aqueous solution. Solid, white budesonide/gamma-CD complex particles were formed using the conventional and modified SEDS processes. The complexation efficiency was dependent on the processing conditions. For example, with the conventional method (100 bar, 60 C) the yield of the powder was 65 +/- 12% with 0.14 +/- 0.02 mg budesonide/mg powder, corresponding to 1:2 drug:CD molar ratio. The dissolution rate of this complexed budesonide (93 +/- 2% after 15 min) was markedly higher compared to unprocessed micronised budesonide (41 +/- 10%) and SEDS-processed budesonide without CD (61 +/- 3%). As a conclusion, SEDS is a novel method to produce solid drug/CD complexes in a single-step process.
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