In-vitro evaluation of sustained-release dyphylline tablets

Dyphylline tablets were prepared by direct compression of mixtures of the drug, emcompress and different ratios of hydroxypropyl methylcellulose (HPMC) or cellulose acetate phthalate (CAP). Physical properties of the prepared tablets and the drug release in 0.1 N HC1 and phosphate buffer, pH 7.4 were investigated.

All tablets were found to satisfy the USP requirements regarding content, weight uniformity and friability. Hardness was greatly enhanced and thickness was slightly increased by increasing the polymer ratio in tablet formulations. Disintegration time of the dyphylline tablets was delayed by the presence of either HPMC or CAP and there was a direct relationship between the polymer ratio and the disintegration time. Considerable retardation in the rate and extent of drug release from the prepared tablets in both dissolution liquids was observed. As the polymer ratio increased in the tablet formulations, the drug release was significantly inhibited.     

Computational complexities of axiomatic extensions of monoidal t-norm based logic

We study the computational complexity of some axiomatic extensions of the monoidal t-norm based logic (MTL), namely NM corresponding to the logic of the so-called nilpotent minimum t-norm (due to Fodor in Fuzzy Sets Syst 69:141–156, 1995); and SMTL corresponding to left-continuous strict t-norms, introduced by Esteva (and others) (Fuzzy Sets Syst 132(1):107–112, 2002; 136(3):263–282, 2003). In particular, we show that the sets of 1-satisfiable and positively satisfiable formulae of both NM and SMTL are NP-complete, while the set of 1-tautologies of NM and the set of positive tautologies of both NM and SMTL are co-NP-complete. The set of 1-tautologies of SMTL is only shown to be co-NP-hard, and it remains open if this set is in co-NP. Also, some results on the relations between these sets are obtained. We point out that results about 1-satisfiability and 1-tautology for NM are already well-known. However, in this paper, those results are proved in different ways. W. B. Lotfallah is on leave from Cairo University.     

SOLIDS DISTRIBUTION IN A BATCH BUBBLE COLUMN

This paper presents some new experimental data for axial solid distribution in batch slurry reactors. The effects of liquid and solid properties on the solid dispersion behavior in 0.076 m and 0.305 m diameter slurry bubble columns are outlined. The effects of gas distributor, column internals and particle size distribution on the solids concentation profiles are also examined. Critical gas velocity for complete suspension of solids are measured and compared with those predicted from the available literature correlations. It is shown that when the particles are completely suspended, the Peclet number obtained from the sedimentation-dispersion model depends very significantly on the assumed boundary conditions. The effect of gas velocity on the particle Peclet number depends on the nature of the liquid-solid system.     

Effect of environmental fluctuations on the dynamic composition of engineered cartilage: a deterministic model in stochastic environment

Dynamics of extracellular matrix (ECM) deposition and scaffold degradation in cell-polymer constructs have been studied in a random fluctuating environment created due to the applications of growth factors into the in vitro generation of cartilaginous constructs. Existing models of cell-polymer constructs for the design of engineered cartilage have been discussed and then a new deterministic scheme in random environment proposed taking into account the effects of growth factors as the environmental variability in the form of Gaussian white noise. Steady-state probability distribution of each individual component of the ECM in its homeostasis is found explicitly. The computer-simulated results of the model have been discussed and then compared with the data from a variety of scaffold systems and culture conditions.     

The effect of angle on wall shear stresses in a LIMA to LAD anastomosis: numerical modelling of pulsatile flow

The purpose of this study was to examine the effect of anastomotic angle on the flow patterns and wall shear distributions at the distal anastomosis of a left interior mammary artery (LIMA) graft to the left anterior descending artery (LDA). It is now well recognized that abnormal wall shear stress distributions along the anastomotic bed, around the toe, and around the heel can contribute to the focal development of intimal hyperplasia. However, the exact nature of the interaction between the dominant pulsing flow and the anastomotic angle on wall shear stresses has not been fully investigated numerically. In this study a commercial CFD package was used for three-dimensional flow analysis where the pulsatile waveforms and flowrates used as the boundary conditions are representative of an anastomosed left internal mammary artery and a stenosed left anterior descending coronary artery (intermediate, <70 per cent diameter narrowing). The flow patterns and distributions of time-averaged wall shear stress (TAWSS) and the oscillatory shear index (OSI) for three anastomotic angles of 20, 40, and 60 degrees were evaluated and compared with other published data. The findings indicated that transient, highly disturbed flow patterns occurred in localized regions of the proximal and distal native segments and in the anastomotic domain including recirculation zones, moving points of stagnation, and oscillating wall shear stresses mainly on the bed, at the toe, and at the heel. Moreover, higher anastomotic angles resulted in more extreme variations in TAWSS and OSI values, particularly around the toe and along the bed. In addition, the effect of anastomotic angle on OSI values at the heel followed the same pattern whereas the TAWSS values along the graft at the heel showed a significant increase at the lowest anastomotic angle of 20 degrees.     

Rapid processing & characterization of micro-scale functionally graded porous materials

Spark plasma sintering (SPS) is a process that has stimulated worldwide interest for the rapid consolidation of powder-based materials through the combined effects of electric current and pressure. Recently the localization of SPS has been realized through current activated tip-based sintering (CATS) where electric current is selectively applied to small targeted regions of a green compact/powder bed via a precision controlled electrically conductive small tip. The unique tip-specimen geometry allows for locally controlled temperature and current distributions that can result in microstructural modifications on the micro-scale. The present paper presents for the first time the rapid processing and characterization of micro-scale functionally graded materials in relation to porosity content and size. The effects of initial green density and particle size on the developed micro-scale functionally graded material are discussed.