Research Papers: Preparation of Indobufen Pellets by Using Centrifugal Rotary Fluidized Bed Equipment Without Starting Seeds

ABSTRACT

Pellets containing Indobufen as model drug were prepared by using the centrifugal-rotary fluidized bed equipment without employing non-pareil seeds.

The influence of different amounts of spheronization enhancer (microcrystalline cellulose) and of different fillers (lactose, mannitol, calcium carbonate) on both processing and physical properties of the pellets were evaluated.

The preparation reproducibility was also investigated. The use of 30% w/w of microcrystalline cellulose was essential to produce a good quality pellets; the incorporation of filler decreased the qualitative characteristics of the pellets.

The water feeding rate proved to be an important parameter for the pellet growth.

Therefore, the results showed that this technology based on the rotary fluidized bed is a promising and alternative method in producing pellets.     

Zero-Safe Nets: Comparing the Collective and Individual Token Approaches

The main feature of zero-safe nets is a primitive notion of transition synchronization. To this aim, besides ordinary places, called stable places, zero-safe nets are equipped with zero places, which in an observable marking cannot contain any token. This yields the notion of transaction: A basic atomic computation, which may use zero tokens as triggers, but defines an evolution between observable markings only. The abstract counterpart of a generic zero-safe net B consists of an ordinary P/T net whose places are the stable places of B and whose transitions represent the transactions of B. The two nets offer the refined and the abstract models of the same system, respectively, where the former can be much smaller than the latter, because of the transition synchronization mechanism. Depending on the chosen approach—collective vs individual token philosophy—two notions of transaction may be defined, each leading to different operational and abstract models. Their comparison is fully discussed on the basis of a multicasting system example. In the second part of the paper, we make use of category theory to analyze and motivate our framework. More precisely, the two operational semantics of zero-safe nets are characterized as adjunctions, and the derivation of abstract P/T nets as coreflections.     

Experimental study of the spontaneous thermal homopolymerization of methyl and n‐butyl acrylate

This article presents an experimental study of the spontaneous thermal homopolymerization of methyl acrylate (MA) and n‐butyl acrylate (nBA) in the absence of any known added initiators at 120 and 140°C in a batch reactor. The effects of the solvent type, oxygen level, and reaction temperature on the monomer conversion and polymer average molecular weights were investigated. Three solvents, dimethyl sulfoxide (DMSO; polar, aprotic), cyclohexanone (polar, aprotic), and xylene (nonpolar) were used. The spontaneous thermal polymerization of MA and nBA in DMSO resulted in a lower conversion and higher average molecular weights in comparison to polymerization in cyclohexanone and xylene under the same conditions. The highest final conversion of both monomers was obtained in cyclohexanone. The high polymerization rate in cyclohexanone was most likely due to an additional initiation mechanism where cyclohexanone complexed with the monomer to generate free radicals. Bubbling air through the mixture led to a higher monomer conversion during the early stage of the polymerization and a lower polymer average molecular weight in xylene and cyclohexanone; this indicated the existence of a distinct behavior between the air‐ and nitrogen‐purged systems. Matrix‐assisted laser desorption/ionization time‐of‐flight analysis of the polymer samples taken from nitrogen‐bubbled batches did not reveal fragments from initiating impurities. On the basis of the identified families of peaks, monomer self‐initiation is suggested as the principal mode of initiation in the spontaneous thermal polymerization of MA and nBA at temperatures above 100°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Selective effect of cholesterylphosphoserine on intracellular cholesterol transport

Cholesteryl-3β-phosphoserine (CPHS) is a synthetic steroid affecting intracellular cholesterol transport. To compare CPHS with the well-known inhibitors progesterone and U18666A, we examined cholesterol transport in three human cell lines: the monocytic U-937, the endothelial ECV-304, and the lymphoid Jurkat. Under low density lipoprotein (LDL) loading, CPHS inhibited cholesterol esterification in U-937 and ECV-304 cells but not in Jurkat cells. In contrast, CPHS inhibited the mobilization of plasma membrane cholesterol induced by 25-hydroxycholesterol, brefeldin A, or sphingomyelinase in all cell lines. In cells pulse-labeled with [³H] cholesterol, CPHS decreased incorporation of cholesterol and inhibited its esterification. In prelabeled cells, CPHS promoted cholesterol efflux and enhanced the cyclodextrin-mediated removal of plasma membrane cholesterol. CPHS did not affect endogenous cholesterol synthesis nor acylcoenzyme A: cholesterol acyltransferase activity. These data suggest that, unlike progesterone and U18666A, CPHS inhibits intracellular cholesterol transport by specifically affecting the movements of cholesterol in the plasma membrane. Owing to this restricted site of action, CPHS may help to clarify the role of the plasma membrane in cholesterol trafficking. For example, the lack of an effect of CPHS on the esterification of LDL-derived cholesterol in Jurkat cells suggests that most of the LDL-derived cholesterol in these cells is directly delivered to the endoplasmic reticulum without cycling through the plasma membrane.     

Semantic foundations for generalized rewrite theories

Rewriting logic (RL) is a logic of actions whose models are concurrent systems. Rewrite theories involve the specification of equational theories of data and state structures together with a set of rewrite rules that model the dynamics of concurrent systems. Since its introduction, more than one decade ago, RL has attracted the interest of both theorists and practitioners, who have contributed in showing its generality as a semantic and logical framework and also as a programming paradigm. The experimentation conducted in these years has suggested that some significant extensions to the original definition of the logic would be very useful in practice. These extensions may develop along several dimensions, like the choice of the underlying equational logic, the kind of side conditions allowed in rewrite rules and operational concerns for the execution of certain rewrites. In particular, the Maude system now supports subsorting and conditional sentences in the equational logic for data, and also frozen arguments to block undesired nested rewrites; moreover, it allows equality and membership assertions in rule conditions. In this paper, we give a detailed presentation of the inference rules, model theory, and completeness of such generalized rewrite theories. Our results provide a mathematical semantics for Maude, and a foundation for formal reasoning about Maude specifications.     

SystemC cosimulation and emulation of multiprocessor SoC designs

SystemC is an open source C/C++ simulation environment that provides several class packages for specifying hardware blocks and communication channels. The design environment specifies software algorithmically as a set of functions embedded in abstract modules that communicate with one another and with hardware components via abstract communication channels. It enables transparent integration of instruction-set simulators and prototyping boards. The authors describe a simulation environment that targets heterogeneous multiprocessor systems. They are currently working to extend their methodology to more complex on-chip architectures.     

Multicomponent crystals of gliclazide and tromethamine: preparation,physico-chemical,and pharmaceutical characterization*

Objective: To improve the pharmaceutical behavior of the oral antidiabetic agent gliclazide through the synthesis of multicomponent crystals with tromethamine.

Methods: Multicomponent crystals were prepared by solvent evaporation method, kneading, and combining mechanical and thermal activation. DSC, FT-IR spectroscopy, X-ray diffraction, SEM-EDS, and SSNMR were used to investigate their formation. Measurements of solubility and dissolution rate were carried out for the pharmaceutical characterization.

Results: The formation of multicomponent crystals of gliclazide and tromethamine was confirmed by all the techniques. In particular, FT-IR and NMR measurements revealed that the interaction between drug and coformer leads to significant changes of the hydrogen bond scheme, and that almost all the functional groups of the two molecules are involved. The dissolution profile of the new phase is significantly better than that of both pure gliclazide and of the reference commercial product Diabrezide^®.

Conclusions: The new system shows an improved pharmaceutical behavior and could be formulated in a dosage form to obtain a rapid and complete release of the drug available for absorption.