Willem Frans Stevens

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Mutagenesis was used to probe the interface between the small GTPase Cdc42p and the CRIB domain motif of Ste20p. Members of a cluster of hydrophobic residues of Cdc42p were changed to alanine and/or arginine. The interaction of the wild-type and mutant proteins was measured using the two-hybrid assay; many, but not all, changes reduced interaction between(More)
Factors affecting Lactobacillus fermentation of shrimp waste for chitin and protein liquor production were determined. The objective of the fermentation is medium conditioning by Lactobacillus through production of proteases and lowering of the pH. The efficiency was tested by conducting fermentation of biowaste in 1-l beakers with or without pH adjustment(More)
Chitosan prepared from natural biopolymer chitin and cast into membranes has been tested as wound dressing at the skin-graft donor site in patients. Bactigras, a commonly used impregnated tulle gras bandage, served as a control. Chitosan membrane, prepared with a 75% degree of deacetylation and a thickness of 10 microm, was used in nonmesh or mesh form. The(More)
The aim of this study is to develop multilayer beads with improved properties for controlled delivery of the antibiotic ampicillin. Ionotropic gelation was applied to prepare single and multilayer beads using various combinations of chitosan and Ca(2+) as cationic components and alginate and polyphosphate as anions. Beads prepared with higher concentrations(More)
Chitosan-alginate beads loaded with a model protein, bovine serum albumin (BSA) were investigated to explore the temporary protection of protein against acidic and enzymatic degradation during gastric passage. Optimum conditions were established for preparation of homogenous, spherical, and smooth chitosan-alginate beads loaded with BSA. Multilayer beads(More)
A hybrid fuzzy-SVM classifier, used to automate leukaemia diagnosis based on microarray gene expression data, is presented. A publicly available dataset was used to develop and test the classifier. A fuzzy gene filter was developed to select the genes which show significant class variation between various leukaemia types. The results obtained from using all(More)
The amount of traffic generated by RTAs has increased substantially over the years. RTA will face congestion where there is any form of bottleneck restricting traffic. This will result in packet loss or delayed traffic which is unacceptable for RTAs. Therefore it is desirable for RTAs to implement congestion control mechanism to improve the stability of(More)
The solubility of non cross-linked chitosan in weak acid solutions restricts its utility in microspheres for drug delivery. The primary aim of this study was to produce pentasodium tripolyphosphate cross-linked chitosan microspheres with higher acid resistance for controlled release of ampicillin. The microspheres were prepared by two different(More)
Fermentation of shrimp biowaste was conducted with two Lactobacillus plantarum strains at pH=6.0 under various salt concentrations. The non-amylolytic strain L. plantarum 541 and amylolytic strain L. plantarum A6 showed to possess reasonable growth in biowaste with the addition of salt as high as 6 %. Fermentation carried with 10 % inoculum, 5 % glucose,(More)
The transcription pattern of bacteriophage Mu has been studied with the use of Mu-1 cts62, a thermo-inducible derivative of wild-type Mu. The rate of transcription at various times after induction was measured by pulse-labeling the RNA during synthesis and determining the fraction of Mu-specific RNA by hybridization with the separated strands of Mu-DNA.(More)