The application of biopharmaceuticals for oral administration is a topic of great interest in the pharmaceutical industry due to the inherent advantages of oral delivery [1]. Biopharmaceutical formulations are more stable in the solid state than in liquid form; in addition, it has many advantages like storage at ambient temperature, longer shelf-life, easier product shipping and the possibility of controlled drug delivery [2]. Currently, the pharmaceutical industry is typically applying freeze drying and spray drying processes in order to obtain solid biopharmaceuticals, however, both technologies have disadvantages [3,4]. Freeze drying is a time-consuming batch technology, has high energy consumption, and the freezing can cause degradation of the biomolecules. On the contrary, spray drying can be operated continuously, is more economical, but can induce inactivation of heat-sensitive molecules, due to the high drying temperature. Electrospinning (ES), which is originally a fiber drawing technology, can be a promising alternative for continuous drying technologies, providing Abstract. Electrospinning is a promising drying technology providing a rapid and gentle drying at ambient temperature, thus electrospinning of polyvinyl alcohol aqueous solutions was investigated for the solid formulation of biopharmaceuticals. The commonly used single-needle electrospinning does not have adequate productivity to satisfy the industrial requirements, therefore our aim was to study the scale-up of the technology by using high-speed electrospinning. High molecular weight polyethylene oxide as a secondary polymer was applied to enhance the fiber formation of polyvinyl alcohol. While polyvinyl alcohol-polyethylene oxide formulations resulted in adequate fiber formation it was not possible to process them further as the friability of the fibers was too low. In order to increase the friability, the effect of adding various sugars (mannitol, glucose, lactose, saccharose, and trehalose) was investigated. The results showed that mannitol was the best friability enhancing excipient because of its crystallinity and low moisture content in the fibrous sample. In contrast, glucose, lactose, saccharose, and trehalose were amorphous with higher moisture content and fibers containing these were grindable only after post-drying.
In this work a cycloaliphatic amine-cured epoxy (EP) resin was modified by micron-scale rubber particles (RP). Nominal RP, in sizes of 200 and 600 µm respectively, were produced using worn truck tires and ultra-high-pressure water jet cutting. The RP were dispersed into the EP resin using different mixing techniques (mechanical, magnetic, and ultrasonic stirring) prior to the introduction of the amine hardener. The dispersion of the RP was studied using optical light microscopy. A longer mixing time reduced the mean size of the particles in the EP compounds. Static (tensile and flexural), dynamic (unnotched Charpy impact), and fracture mechanical (fracture toughness and strain-energy release rate) properties were determined. The incorporation of the RP decreased the stiffness and strength values of the modified EPs. In contrast, the irregular and rough surface of the RP resulted in improved toughness. The fracture toughness and strain-energy release rate were enhanced up to 18% owing to the incorporation of 1% by weight (wt%) RP. This was traced to the effects of crack pinning and crack deflection. Considerably higher improvement (i.e., up to 130%) was found for the unnotched Charpy impact energy. This was attributed to multiple cracking associated with RP-bridging prior to final fracture.
In case of traditional surface-hardening processes (e.g. carburization), the wear resistance usually correlates with hardness, which means optimising these technologies could be based on testing the achieved hardness. In case of modern laser treatment technologies however – e.g. surface melting combined with surface alloys or laser scanning surface treatment followed by nitridation – it is unlikely to conclude wear resistance from the value of hardness. The reasons are the following: the hardness of surface melting combined with surface alloys (especially if alloyage is made using high hardness compound powders) depends on the remelting of the material and the particle size and distribution of the dispersed alloy. These same properties define wear resistance, but the values don’t necessarily correlate. In case of a compound phase dispersion in a softer base material, we can have outstanding wear resistance with moderate hardness. (e.g. bearing metals) The case is similar with scanning treatment combined with nitridation, which results in complicated structures. Due to the above, it is possible that in order to optimise these aforementioned technologies, we have to rely on examining wear resistance. In order to back this statement, we show the results of two typical experiments concerning these technologies.
. A method for the structural classification of fullerenes via graph invariants is presented. These graph invariants (called edge-parameters) represent the 9 different types of bonds existing in fullerenes between two neighbouring carbon atoms and they are also applicable to classify the fullerene isomers into equivalence classes. Discriminating performance of edge-parameters has been tested on the sets of C40 and C66 fullerene isomers. It is shown that the stability of C40 and C66 isomers can be efficiently predicted using a novel topological descriptor (Ω) defined as a function of four appropriately selected edge parameters.
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