The influence of chitosan on in vitro properties of Eudragit RS microspheres

Eudragit RS microspheres containing chitosan hydrochloride were prepared by the solvent evaporation method using acetone/liquid paraffin solvent system and their properties were compared with Eudragit RS microspheres without chitosan, prepared in our previous study. Different stirring rates were applied (400-1200 rpm) and drug content, Higuchi dissolution rate constant, surface and structure characteristics of the microspheres were determined for each size fraction. An increase in average particle size with a reduction of stirring rate appeared in limited interval in both series. The average particle size of microspheres without chitosan, prepared at the same stirring rate, was smaller. Pipemidic acid content increased with increasing fraction particle size, but not with increasing stirring rate as it was observed for microspheres without chitosan. We presume that high pipemidic acid content in larger microspheres is a consequence of cumulation of undissolved pipemidic acid particles in larger droplets during microspheres preparation procedure. Pipemidic acid release was faster from microspheres with chitosan and no correlation between Higuchi dissolution rate constant and stirring rate or fraction particle size was found, though it existed in the system without chitosan. Structure and surface characteristics of microspheres observed by scanning electron microscope (SEM) were not changed significantly by incorporation of chitosan. But in contrast with microspheres without chitosan, the surface of chitosan microspheres was more porous after three hours of dissolution. It is supposed that the influence of particle size fraction and stirring rate on release characteristics is expressed to a great extent through porosity and indirectly through total effective surface area, but the incorporation of highly soluble component i.e. chitosan salt hides these effects on drug release. In conclusion, changes in biopharmaceutical properties due to varying stirring rate and fraction particle size exhibited the same direction as those reported for the microspheres without chitosan, although they are less expressed because of increased experimental variability, likely caused by chitosan.     

OR in the industrial engineering of Industry 4.0: experiences from the Iberian Peninsula mirrored in CJOR

Central European Journal of Operations Research - Industry 4.0 (I4.0) implies a group of technologies, organisational concepts and management principles to improve the performance of manufacturing...     

Effect of preparation temperature in solvent evaporation process on Eudragit RS microsphere properties

Eudragit RS 100 microspheres containing ketoprofen as a model drug were prepared by the solvent evaporation method using an acetone/liquid paraffin solvent system. The influence of various preparation temperatures: 10, 25, 35, and 40 degrees C, on particle size and morphology, drug content and release kinetics, and drug crystal state was evaluated. With increasing temperature, microsphere average size was found to increase and particle size distribution to widen significantly. At 10 degrees C particles of irregular shape are formed, whereas higher temperatures gradually improve the sphericity of microspheres. As can be seen from SEM photographs, particle surface roughness decreases as preparation temperature increases. It was found that temperature had no effect either on ketoprofen microencapsulation efficiency or on its crystal state, but it does influence emulsion-stabilizer incorporation. Ketoprofen forms solid solution in Eudragit matrix and maintains amorphous state for significant period of time. Drug release rates from microspheres correlated with microspheres' surface roughness and to a lesser extent with particle size.     

Reverse logistics facility location using cyclical model of extended MRP theory

Grubbström’s well-developed MRP Theory has been mostly used in modeling production processes. Global supply chains also contain distribution, consumption and recycling processes. For this reason theory was recently further extended to incorporate all kinds of activities. Such extended model, which consists of four main sub-systems, is closed and can be used for several detailed analyses. Since the importance of reverse logistics is increasing, this paper will focus on parameters which determine Net Present Value of the whole system, depending on geographical location of recycling facilities. We will show how lead times, transportation costs, setup costs and price of labor and energy of individual location contribute to overall NPV of the system.     

An approximate algorithm for optimal logistics of heavy and variable size items

The objective of this article is to show the improvement reached by a ceramic logistics operator using an approximate algorithm for cargo of logistics of many different products with different weights and volumes. This algorithm, which has been used successfully for efficient assignment in logistics industry, where many different products in small but heavy items have to be distributed, can improve road transport efficiency for clients’ orders in the minimum time and with the least possible costs. The paper describes how it could increase efficiency in logistics in a ceramic industry (from the initiation of activities and over several days to the end of the job cycle) and similar heavy and small items production when time and costs play the role in function criterion. The algorithm is based on several priority rules. Real life application of the algorithm developed here has been running on a time horizon of more than one week. Though the results of the first steps (initial solution) of algorithm are not as good as the results of already known algorithms for transportation assignments, the algorithm is improving the value of criterion function rapidly, during further iterations dealing with the sequences of daily assignments, which is a major improvement in applications for such types of algorithms, known up until now. The algorithm was a well accepted development and seen as very beneficial to the ceramics industry.     

Multistage reverse logistics of assembly systems in extended MRP Theory consisting of all material flows

In this paper we will address the issue of environmental problems in connection with extended MRP Theory. It is based on Grubbstr?m??s well developed MRP Theory (Grubbstr?m in Z für BetrWirthsch 77(3):297?C324, 2007). A major advantage of this theory is that timing and its impact on net present value can be easily calculated even for extended multilevel, multistage production-inventory systems and also for perturbed production systems consisting of many production cells. Theory has recently been extended by including reverse logistics of final and used products (Grubbstr?m et?al. in A compact representation of distribution and reverse logistics in the value chain. Faculty of Economics, Ljubljana, 2007). At each activity cell a certain percentage of scrapes is produced and sent for recycling after quality control. Here we present an input?Coutput model which includes all possible flows into a recycling sub-process with several stages of recycling. This model is presented in a generalized form of input and output matrices which has not been developed before. The model will be presented in two different ways which differ in the level of detailed information they contain. Contribution of recycling to the net present value of all activities in a supply chain is expressed and can be compared to environmental damage that could occur if reverse processes are not introduced. Using this approach, the losses and gains in both the economy and the environment could be evaluated more accurately considering all individual flows in the system. No other approaches besides input?Coutput analysis and Laplace transforms have been found so successful in compound supply systems.     

Regression-fuzzy approach to land valuation

In this paper, we demonstrate that the fuzzy pricing model can improve regression analysis in applications where non-smoothness appears. Combining the fuzzy and regression approaches it is capable of modelling complex non-linearities. The application of this approach describes an effort to design a regression-fuzzy system to estimate real estate market values, especially for vacant urban plots. The results are compared with those obtained using a traditional multiple regression model only. The changes of parameters in the domain of independent variables of the regression function are determined by the analysis of membership functions defining the terms of the fuzzy model. The paper also describes possible future research. The suggested method is interesting for real estate appraisers, real estate companies, and bureaus because it provides a better overview of location prices. The suggested approach could be also used in various other economic and business analyses.     

Optimisation of short term commercial bank loans to corporates in terms of financing operating activities in Slovenia

This paper presents the mathematical model for determination of the optimal amount of short term commercial bank loans to corporate sector in Slovenia which is based on probabilistic inventory models. The goal of this paper is complete optimisation of cash inventories of corporate sector in the national economy. The results of optimisation are important for the corporate sector and for commercial banks. The optimal order quantity is an amount of short term commercial bank loan to corporates and defines a lending potential of commercial banks in a national economy. As such is important for the central bank when conducting monetary policy. Special emphasis has been given to determinants of optimal order quantity, which reflect market conditions in national economy.     

Network Simulation Method for the evaluation of perturbed supply chains on a finite horizon

Due to lead times and other delays in a chain, the Net Present Value (NPV) can be easily estimated if Laplace transforms in MRP models are employed. This leads to the estimation of NPV on an infinite horizon. However, for the simultaneous perturbations of several parameters in a supply chain and activities running on the finite horizon, NPV could be overestimated. Therefore, we suggest the parallel use of the Network Simulation Method (NSM) with the MRP theory to reduce these overestimations. This paper aims to present the NSM to evaluate supply chains on a finite horizon when stochastic behaviour of time delays and other perturbations of parameters are also essential, which is typical for food and drug supply chains. The circuit simulator NGSPICE, which was previously used by certain authors in thermodynamics, also evaluates the financial consequences of simultaneous perturbations in a finite chain. This approach holds better for the stochastic processes of simultaneous perturbations, compared to our results achieved using MRP theory without these corrections. As presented in the numerical example, the shorter the horizon and lower the interest rate, the more important it is to use the correction factors obtained from the NGSPICE simulator.