The effect of the binder size and viscosity on agglomerate growth in fluidised hot melt granulation

Fluidised hot melt granulation (FHMG) is a novel granulation technique for processing pharmaceutical powders. Several process and formulation parameters have been shown to significantly influence granulation characteristics within FHMG. In this study we have investigated the effect of the binder properties (binder particle size and binder viscosity) on agglomerate growth mechanisms within FHMG. Low-melting point co-polymers of polyoxyethylene–polyoxypropylene (Lutrol® F68 Poloxamer 188 and Lutrol® F127 Poloxamer 407) were used as meltable binders for FHMG, while standard ballotini beads were used as model fillers for this process. Standard sieve analysis was used to determine the size distribution of granules whereas we utilised fluorescence microscopy to investigate the distribution of binder within granules. This provided further insight into the growth mechanisms during FHMG. Binder particle size and viscosity were found to affect the onset time of granulation. Agglomerate growth achieved equilibrium within short time-scales and was shown to proceed by two competing processes, breakage of formed granules and re-agglomeration of fractured granules. Breakage was affected by the initial material properties (binder size and viscosity). When using binder with a small particle size (<250 µm), agglomerate growth via a distribution mechanism dominated. Increasing the binder particle size shifted the granulation mechanism such that agglomerates were formed predominantly via immersion. A critical ratio between binder diameter and filler has been calculated and this value may be useful for predicting or controlling granulation growth processes.

The alteration of the structural properties and photocatalytic activity of TiO2 following exposure to non-linear irradiation sources

When TiO2 powder was irradiated with a laser light (>0.8 MW peak pulse power (PPP) at 355 nm) a visible change in its colour from white to dark blue was observed. The initial rate of change of the total colour difference was related to the laser light intensity and the longer the irradiation time the more substantial the colour change. The result of X-ray diffraction (XRD) studies showed that the crystal structure of the TiO2 developed a more rutile form after laser exposure. ESR studies indicated that the colour change was associated with the generation of Ti(III) species in the photocatalyst. Electron microscopic studies showed that more spherical shaped particles of TiO2 were observed after laser treatment although the average particle size remained largely unchanged. No significant changes in the band gap or the surface area of the laser modified TiO2 were observed. The laser modified photocatalyst showed no enhancement in activity for the destruction of methylene blue, rhodamine B and stearic acids, indicating that the rutile/anatase ratio is unimportant in the destruction of the test pollutants used in this work, via TiO2 photocatalysis

Time dependence of the spatial coherence of the 23.6- and 23.2-nm radiation from the germanium soft-x-ray laser

The time dependence of the spatial coherence of the combined spectral lines at 23.2 and 23.6 nm from the Ge XXIII collisionally pumped soft-x-ray laser with a double-slab target is examined within a single nanosecond pulse by use of Young's interference fringes and a streak camera. High source intensity is linked with low spatial coherence and vice verse. Calculations of the source intensity, size, and position have also been made; these calculations refer to a single-slab source. Comparison between the observed and calculated intensities, and of the source sizes both calculated and derived from the Young's fringes by interpretation with a Gaussian model of source emission, show good agreement in general trends. (C) 1998 Optical Society of America [S0740-3224(98)01905-5].

COMPARISON OF THE GROWTH INHIBITORY AND BACTERIOCIDAL EFFECTS OF TAUROLIDINE AND TAURULTAM ON A CLINICAL ISOLATE OF ESCHERICHIA-COLI

To investigate the mode of action of Taurolin, an antimicrobial preparation, the growth inhibitory and bacteriocidal effects of taurolidine and taurultam solutions on Escherichia coli isolated from a diagnosed urinary tract infection were examined at 37-degrees-C. The inhibitory effects of taurolidine solutions were observed to be greater than those of taurultam solutions at comparative concentrations; however, the presence of sublethal concentrations of formaldehyde (methylene glycol) associated with taurolidine was sufficient to account for this. The bacteriocidal activity of taurolidine (2.0% w/v) was greater than that of taurultam (4.5% w/v). Both compounds produced biphasic death rates with dissimilar initial slopes, suggested to be due to the presence of formaldehyde in taurolidine solutions. These observations indicate that the growth inhibitory and bacteriocidal effects of Taurolin solutions are primarily due to taurultam, however, the presence of sublethal concentrations of formaldehyde is significant in the expression of this activity.