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.     

TRANSFORMATION OF n-OCTANE INTO AROMATIC HYDROCARBON OVER ZSM-S ZEOLITES

ABSTRACT

Conversion of n- octane over ZSM-5 zeolites are greatly enhanced by incorporation of 0.35 wt. % Fe, Zn, Zr metals. Hydroconversion rates were conducted at temperature range of 350-500 C, W/F of 14.8 g of catalyst / g. mole of feed / h, and hydrogen / feed = 5:1 (mole : mole). The product selectivity with total conversion was examined at the temperature range under study. The catalyst Zr / H25 M-5 gave the highest selectivity towards aromatization and production of xylenes.     

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.     

A novel approach via combination of electrospinning and FDM for tri-leaflet heart valve scaffold fabrication

In this paper, a novel combination method of electrospinning and rapid prototyping (RP) fused deposition modeling (FDM) is proposed for the fabrication of a tissue engineering heart valve (TEHV) scaffold. The scaffold preparation consisted of two steps: tri-leaflet scaffold fabrication and heart valve ring fabrication. With the purpose of mimicking the anisotropic mechanical properties of the natural heart valve leaflet, electrospun thermoplastic polyurethane (ES-TPU) was introduced as the tri-leaflet scaffold material. ES-TPU scaffolds can be fabricated to have a well-aligned fiber network, which is important for applications involving mechanically anisotropic soft tissues. We developed ES-TPU scaffolds as heart valve leaflet materials under variable speed conditions and measured fiber alignment by fast Fourier transform (FFT). By using FFT to assign relative alignment values to an electrospun matrix, it is possible to systematically evaluate how different processing variables affect the structure and material properties of a scaffold. TPU was suspended at certain concentrations and electrospun from 1,1,1,3,3,3-hexafluoro-2-propanol onto rotating mandrels (200–3000 rpm). The scaffold morphological property and mechanical anisotropic property are discussed in the paper as a function of fiber diameter and mandrel RPM. The induction of varying degrees of anisotropy imparted distinctive material properties to the electrospun scaffolds. A dynamic optimum design of the heart valve ring graft was constructed by FDM. Fabrication of a 3D heart valve ring was constructed using pro-engineer based on optimum hemodynamic analysis and was converted to an STL file format. The model was then created from PCL which was sewed and glued with electrospun nanofibrous leaflets. This proposed method was proven as a promising fabrication process in fabricating a specially designed graft with the correct physical and mechanical properties.     

Effect of mechanical and electrical activation on the combustion synthesis of Al3Ti

Titanium aluminides have attracted immense interest as lightweight intermetallic compounds that possess good high-temperature mechanical and corrosion properties. In the present work, titanium aluminides (Al₃Ti) have been reactively processed from elemental powder using a combined mechanical and electrical activation approach. The effect of mechanical activation and electric current intensity on the ignition and phase development is discussed. Ignition was not possible when powders were milled for a short time, while prolonged milling resulted in mechanical activation that promoted a self-propagating-type reaction. The time to engulfment of the compact with the reaction wave was found to decrease with an increase in current intensity. A secondary reaction occurred at the higher current intensity, which in turn increased the product homogeneity.     

Effect of carbon nanotube (CNT) content on the mechanical properties of CNT-reinforced aluminium composites

The interest in carbon nanotubes (CNTs) as reinforcements for aluminium (Al) has been growing considerably. Efforts have been largely focused on investigating their contribution to the enhancement of the mechanical performance of the composites. The uniform dispersion of CNTs in the Al matrix has been identified as being critical to the pursuit of enhanced properties. Ball milling as a mechanical dispersion technique has proved its potential. In this work, we use ball milling to disperse up to 5 wt.% CNT in an Al matrix. The effect of CNT content on the mechanical properties of the composites was investigated. Cold compaction and hot extrusion were used to consolidate the ball-milled Al–CNT mixtures. Enhancements of up to 50% in tensile strength and 23% in stiffness compared to pure aluminium were observed. Some carbide formation was observed in the composite containing 5 wt.% CNT. In spite of the observed overall reinforcing effect, the large aspect ratio CNTs used in the present study were difficult to disperse at CNT wt.% greater than 2, and thus the expected improvements in mechanical properties with increase in CNT weight content were not fully realized.     

A soft tissue adhesive based on aldehyde-sodium alginate and amino-carboxymethyl chitosan preparation through the Schiff reaction

Sodium alginate and carboxymethyl chitosan have been extensively applied in tissue engineering and other relative fields due to their low price and excellent biocompatibility. In this paper, we oxidized sodium alginate with sodium periodate to convert 1,2-hydroxyl groups into aldehyde groups to get aldehyde-sodium alginate (ASA). Carboxymethyl chitosan was modified with ethylenediamine (ED) in the presence of water-soluble N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) to introduce additional amino groups to get amino-carboxymethyl chitosan (A-CS). Upon mixing the A-SA and A-CS aqueous solutions together, a gel rapidly formed based on the Schiff’s base reaction between aldehyde groups in A-SA and amino groups in A-CS. FTIR analysis confirmed the characteristic peak of Schiff’s base group in the hydrogel. It was confirmed that the gelation time be dependent on the aldehyde group content in A-SA and amino group content in A-CS. The fasted hydrogel formation takes place within 10 min. The data of bonding strength and cytotoxicity measurement also showed that the hydrogel had good adhesion and biocompatibility. All these results support that this gel has the potential as soft tissue adhesive.     

Issues on adjointness in multiple-valued logics

We contribute to the theory of implications and conjunctions related by adjointness, in multiple-valued logics. We suggest their use in Zadeh’s compositional rule of inference, to interpret generalized modus ponens inference schemata. We provide new complete characterizations of implications that distinguish left arguments, implications that satisfy the exchange principle, divisible conjunctions, commutative conjunctions, associative conjunctions and triangular norms. We also introduce and characterize pseudo-strict and pseudo-continuous implications and conjunctions, and we explore the close relationship between these two notions.