Home About us Contact
|
Home About us Contact | ||
|
|
||
Dispersion Technique (dispersion + technique)
Selected AbstractsAxial liquid mixing in high-pressure bubble columnsAICHE JOURNAL, Issue 8 2003G. Q. Yang Axial dispersion coefficients of the liquid phase in bubble columns at high pressure are investigated using the thermal dispersion technique. Water and hydrocarbon liquids are used as the liquid phase. The system pressure varies up to 10.3 MPa and the superficial gas velocity varies up to 0.4 cm/s, which covers both the homogeneous bubbling and churn-turbulent flow regimes. Experimental results show that flow regime, system pressure, liquid properties, liquid-phase motion, and column size are the main factors affecting liquid mixing. The axial dispersion coefficient of the liquid phase increases with an increase in gas velocity and decreases with increasing pressure. The effects of gas velocity and pressure on liquid mixing can be explained based on the combined mechanism of global liquid internal circulation and local turbulent fluctuations. The axial liquid dispersion coefficient also increases with increasing liquid velocity due to enhanced liquid-phase turbulence. The scale-up effect on liquid mixing reduces as the pressure increases. [source] Improvement of dissolution and oral absorption of ER-34122, a poorly water-soluble dual 5-lipoxygenase/cyclooxygenase inhibitor with anti-inflammatory activity by preparing solid dispersionJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2002Ikuo Kushida Abstract Several formulation approaches were attempted to improve the dissolution and the oral absorption of ER-34122, which is a novel dual 5-lipoxygenase/cyclooxygenase inhibitor with potent anti-inflammatory activity. The solid dispersion of ER-34122 with hydroxypropylmethylcellulose (TC-5RW), which is an inert solid carrier, resulted in a significant improvement in the dissolution rate of ER-34122. The solid dispersion was prepared by a solvent evaporation method using ethanol and water. The solid-state characteristics of the solid dispersion, the corresponding physical mixture, and ER-34122 alone were investigated by X-ray powder diffraction, Fourier transform infrared spectroscopy (FTIR), and an automated controlled-atmosphere microbalance. The X-ray powder diffraction patterns suggest that the solid dispersion exists in a totally amorphous state and the others exist in a crystalline state. The FTIR spectra results suggest that ER-34122 can interact with TC-5RW through intermolecular hydrogen bonding in the solid dispersion. This interaction may cause a stabilization of ER-34122 in the higher-energy, faster-dissolving amorphous state. The dissolution rate of ER-34122 from the solid dispersion was significantly greater than that from the physical mixture or the pure drug. Furthermore, when orally administrated to beagle dogs, ER-34122 showed about a 100-fold increase in both maximum concentration (Cmax) and area under the curve of concentration versus time (AUC) compared with the pure drug. Consequently, it was determined that the solid dispersion technique with TC-5RW provides a promising way to increase the dissolution rate and the oral absorption of poorly water-soluble drugs such as ER-34122. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:258,266, 2002 [source] Enhanced solubility and dissolution rate of lamotrigine by inclusion complexation and solid dispersion techniqueJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 9 2008Vikram R. Shinde ABSTRACT The solid-state properties and dissolution behaviour of lamotrigine in its inclusion complex with ,-cyclodextrin (,CD) and solid dispersions with polyvinylpyrrolidone K30 (PVP K30) and polyethyl-eneglycol 6000 were investigated. The phase solubility profile of lamotrigine with ,CD was classified as AL -type, indicating formation of a 1:1 stoichiometry inclusion complex, with a stability constant of 369.96 ± 2.26 M,1. Solvent evaporation and kneading methods were used to prepare solid dispersions and inclusion complexes, respectively. The interaction of lamotrigine with these hydrophilic carriers was evaluated by powder X-ray diffractometry, Fourier transform infrared spectroscopy and differential scanning calorimetry. These studies revealed that the drug was no longer present in crystalline state but was converted to an amorphous form. Among the binary systems tested, PVP K30 (1:5) showed greatest enhancement of the solubility and dissolution of lamotrigine. [source] Processability studies of silica-thermoset polymer matrix nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 2 2008C. Lekakou The aim of this study is to investigate the processability of silica-thermoset polymer matrix nanocomposites in terms of dispersion of silica nanoparticles and their effect on curing. Two thermosetting resins were considered, an epoxy and a polyester resin, with 5% silica, although 1% silica was also used in preliminary studies in the polyester system. Various combinations of mechanical mixing and sonication were investigated for the dispersion of silica nanoparticles under different processing conditions and times in solvent-free and solvent-containing systems. It was found that the best dispersion route involved a solvent-aided dispersion technique. Consequently, different procedures for the solvent removal were investigated. Optical microscopy and SEM were used to characterize the resulting nanocomposites. DSC and rheological DMTA tests demonstrated that the silica nanoparticles shorten the gel time and promote curing in these thermosetting systems. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers [source] Hyperstability and crystal structure of cytochrome c555 from hyperthermophilic Aquifex aeolicusACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2009Marii Obuchi In order to elucidate the relationship between the stability and the structure of the monohaem cytochrome c555 (AA c555) from the hyperthermophilic bacterium Aquifex aeolicus, chemical denaturation and crystal structure determination were carried out. AA c555 exhibited higher stability than the thermophilic Hydrogenobacter thermophilus cytochrome c552 (HT c552), which is one of the most stable cytochromes c. The three-dimensional crystal structure of AA c555, which was determined using the multiple anomalous dispersion technique at 1.15,Å resolution, included a unique 14-residue extra helix, while the side-chain interactions of several amino-acid residues responsible for the stability of HT c552 were conserved in AA c555. The side chain of the Met61 residue in the extra helix was aligned towards the haem, forming a coordination bond between the Met S and haem Fe atoms. In other cytochromes c the corresponding regions always form , loops which also include the haem-liganding Met residue and are known to be involved in the initial step in cytochrome c denaturation. The formation of the extra helix in AA c555 results in the highest helix content, 59.8%, among the monohaem cytochromes c. The extra helix should mainly contribute to the hyperstability of AA c555 and is presumed to be a novel strategy of cytochromes c for adaptation to a hyperthermophilic environment. [source] | ||||||||||