Showing papers by "University of Twente published in 1985"

Studies on tableting properties of lactose. Part 2. Consolidation and compaction of different types of crystalline lactose.

Abstract: Lactose is available in several crystalline forms, which differ in binding properties. A new method of estimating the fragmentation propensity was applied to investigate the consolidation and compaction behaviour of this excipient for direct compression. Mercury porosimetry was used to demonstrate that crystalline lactose fragments during compaction. Tablet strength was found to be dependent on the degree of fragmentation only. This finding indicates that the nature of the actual binding must be the same for the different types of crystalline lactose.

A rationale for the preparation of asymmetric pervaporation membranes

Abstract: Pervaporation is carried out primarily with homogeneous membranes. An improvement in permeation rate can be achieved by using asymmetric or composite membranes. In order to maintain a high selectivity, very dense top layers are needed. The formation of asymmetric pervaporation membranes will be discussed in terms of the model proposed by our group: formation of the top layer by gelation; formation of the porous sublayer by liquid-liquid phase separation followed by gelation of the concentrated polymer phase. To obtain very dense top layers the following factors are important: the ratio of nonsolvent inflow and solvent outflow, polymer concentration, location of the liquid-liquid demixing gap, and location of the gel region. Asymmetric membranes have been prepared by varying these factors, and the obtained membranes have been tested on ethanol/water mixtures.

Phase separation phenomena in solutions of poly(2,6‐dimethyl‐1,4‐phenyleneoxide) in mixtures of trichloroethylene, 1‐octanol, and methanol: Relationship to membrane formation

Abstract: The phase boundaries in the quaternary system consisting of the polymer poly(2,6-dimethyl-1,4-phenyleneoxide) (PPO[Note ][PPO is a registered trademark of the General Electric Company.]), the solvent trichloroethylene (TCE), and the nonsolvents 1-octanol (OcOH) and methanol (MeOH) are determined. The kinetics of crystallization are investigated by pulse-induced critical scattering. The formation and properties of PPO membranes are discussed in relation to the phase separation phenomena.

Two politicians in a realistic experiment: attraction, discrepancy, intensity of delivery, and attitude change

Abstract: The leader of the Socialists in the Dutch Parliament and his Liberal opponent participated in this realistic experiment. Identical TV interviews with the two politicians were recorded and shown to subjects of both parties. The intensity of delivery was also varied: emotional versus rational. Our findgins indicated that the experimental interveiw changed the attitude of the subjects. In addition, support was found for a second hypothesis: Attitude change was greater for the attractive source from the same party than for the less attractive source from the opposite party. Furthermore, our expectations were confirmed that attitude change would be greater with high than with low discrepancy. Although the intensity of delivery did have an effect on the credibility of the source–the emotional delivery scored lower–no effect on attitude change was found.

Adhesion of coagulase-negative staphylococci with different surface characteristics onto a hydrophobic biomaterial

Abstract: Implanted prostheses or temporary inserted medical devices are frequently associated with infections. Coagulase-negative staphylococci (CNS) are most often isolated from such infections (Garvey, 1980). The adhesion of the CNS onto the surface of the devices has been considered to play an essential role in the initiation of infections (Peters et al., 1982; Sugarman, 1982). In this study surface characteristics of various strains of CNS such as hydrophobicity, relative negative surface charge and the presence of capsules, were determined. Subsequently, the adhesion of various strains of Staphylococcus epidermidis and S. saprophyticus onto fluorinated polyethylenepropylene (FEP), a hydrophobic biomateral was studied. Since surfaces of devices after contact with blood or body fluids are rapidly coated with a protein layer (Feijen et al., 1979) we also studied the bacterial adhesion onto FEP pre-exposed to plasma. CNS used in this study were isolated from the skin and from the blood of open heart surgery patients with sepsis or with endocarditis. The strains were classified according to the scheme of Kloos and Schleifer (1975) using the API Staph gallery. In total, 22 strains of S. epidermidis, 21 strains of S. saprophyticus, 10 strains of S. capitis, 10 strains of S. haemolyticus, 8 strains of S. hominis, 4 strains of S. cohnii and 2 strains of S. warneri were identified.

A Four-Quadrant CMOS Analog Multiplier

Abstract: A new circuit configuration for an MOS four-quadrant analog multiplier circuit is presented. It is based on the square-law I-V characteristics of the MOS transistor. Linearity is better then 0.14 % for an output swing of 36 % of the supply current. The bandwidth is from de to above 1 MHz.

FORTH ― A good programming environment for laboratory automation ? II: An example from the laboratory

Abstract: The query which (x: acetylsalicylic-acid to-be-dissolved-in x) yields then: dilute-NaOH. This knowledge base consisting of sentences and rules can now be extended at will. For instance if one wants to know in which solvent one should dissolve sulfanilamide, a substance containing the functional group sulfonamide, one adds: sulfonamide weak-acidic-function sulfanilamide contains-function sulfonamide and then asks the to-be-dissolved-in query. Alternatively one can add additional rules such as: x to-be-dissolved-in dilute-HCl if (either x acid- base-status weak-base or x acid-base-status strong-base). In this second Corner we have tried to give an idea about how to construct rules in PROLOG. The way in which knowledge was manipulated in these two Corners is simple but not very efficient. Indeed, PROLOG (and similar languages such as LISP) have really been constructed to manipulate lists of knowledge items instead of single items. Lists will be discussed in the next Corner.