Faculty Bibliography

The study investigates the influence of polyvinyl pyrrolidone (PVP) concentration on stabilizing the amorphous form of salbutamol sulphate (SS) before and after storage under ambient and elevated humidity conditions. Different mass ratios of SS and PVP (0-90wt%) were co-milled using a planetary ball mill. X-ray powder diffraction (XRPD), high sensitivity differential scanning calorimetry (HSDSC), dynamic vapor sorption (DVS), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Raman microscopy (RM) were used to analyze the stability of the co-milled mixtures against heat and humidity treatments as well as storage at different humidity conditions. Prior storage, DSC and DVS analyses revealed that re-crystallization of amorphous SS was suppressed above PVP content of 33 wt%. Probable hydrogen bond interaction between SS and PVP was found in FT-IR analysis. XRPD diffractograms and SEM analysis showed stability against re-crystallization was achieved in the co-milled mixtures with a minimum PVP content of 80 wt% after storage. Homogeneous distribution of SS and PVP from RM analysis showed fine clustering of SS and PVP, suggesting the formation of an amorphous dispersion at molecular level. The results provide insights on the application of thermal and humidity treatments, accelerated stability testing and investigations on drug-excipient interactions to predict the minimum ratio of an excipient for stabilizing the amorphous state of a milled API.

1. The study was conducted to evaluate the effects of a dried Bacillus subtilis culture (DBSC) on growth performance and nutrient retention of goslings. 2. A total of 240 goslings were randomly divided into 4 dietary treatments with 6 replicates of 10 goslings per pen from 0 to 4 weeks of age. The 4 treatments consisted of a basal diet containing neither antibiotics nor DBSC (control), basal diet supplemented 5 mg Flavomycin/kg, and basal diet supplemented with 250 or 500 mg DBSC/kg. 3. Body weight and feed consumption were measured with pen as the experimental unit at 14 and 28 d of age, and excreta collections from each pen were carried out to determine nutrient retention ratio during the 4th week. 4. The results showed that the diet supplemented with 250 mg DBSC/kg increased average daily gain (ADG) by 6.9%, reduced average daily feed intake (ADFI) by 3.9%, and improved feed conversion ratio (FCR) by 10.3% in a 0-28 d feeding period, compared with the control diet. However, the diet containing 500 mg DBSC/kg did not effect these performance of goslings. 5. The goslings given the diet with 250 mg DBSC/kg had similar ADG, lower ADFI and significantly lower FCR to or than the goslings fed on the Flavomycin diet. 6. The results also showed that dietary DBSC supplementation improved dry matter and energy retention of goslings. 7. This study indicated that the diet containing a dried B. subtilis culture at 250 mg/kg offered large benefits to the growth performance of goslings, and these benefits could equal or exceed those from Flavomycin. It is suggested that the growth promoting effect of DBSC may be attributed to the improvement in the availability of dietary nutrients.

Breaking down the time limit constraints for conventional compression-permeation (C-P) cell test, this work has, for the first time, experimentally evaluated the cake characteristics of viable waste-activated sludge subject to polyelectrolyte flocculation and to freeze/thaw treatment under a pressure range of 25-200 kPa. There exists a threshold pressure exceeding which the cake structure would significantly deteriorate. Also, the present biological sludge is a "super-compactible" sludge, whose compactibility is greater than most data ever reported in open literature. The information presented herein has implications to filter design/operation and can be used as a reference data set for examining the existing filtration theories.

A genetically structured mathematical model of the trp attenuator in Escherichia coli based on known coupling mechanisms of the transcription of the trp leader region and translation of the trp leader peptide region is proposed. The model simulates, both qualitatively and quantitatively, the effects of tryptophan on the repression of cloned gene products. It shows that repression by attenuation mechanism alone operates over a narrow trp concentration range of 1 to 5 microM compared with 1 to 100 microM for trp repressor mechanism. This implies that attenuation by transcription termination is not relaxed until tryptophan starvation is severe. Simulation results show that the attenuator starts to derepress when the repressor is about 40% repressed, and becomes significantly derepressed only when the repressor repression decreased to about 20%. Unlike the case of repressor-operator interaction, the operating range of tryptophan concentration in the attenuator mechanism is not sensitive to plasmid copy number.