Today, monoliths are well-accepted chromatographic stationary phases due to several advantageous properties in comparison with conventional chromatographic supports. A number of different types of ...monoliths have already been described, among them recently a poly(high internal phase emulsion) (PolyHIPE) type of chromatographic monoliths. Due to their particular structure, we investigated the possibility of implementing different mathematical models to predict pressure drop on PolyHIPE monoliths. It was found that the experimental results of pressure drop on PolyHIPE monoliths can best be described by employing the representative unit cell (RUC) model, which was originally derived for the prediction of pressure drop on catalytic foams. Models intended for the description of particulate beds and silica monoliths were not as accurate. The results of this study indicate that the PolyHIPE structure under given experimental condition is, from a hydrodynamic point of view, to some extent similar to foam structures, though any extrapolation of these results may not provide useful predictions of pressure versus flow relations and further experiments are required.
Thrombosis and restenosis are the most common problems during insertion of biocompatible implants like titanium stents into human blood, due to aggregation of platelets on their surfaces. Because of ...this reason, we studied the response of blood platelets to a plasma treated titanium surface. The aim was to design a functionalized surface which would repel blood platelets or prevent their adhesion. Therefore, we functionalized surfaces with low-temperature inductively coupled oxygen plasma treatment, which in the first stage cleaned the surface of titanium, and in the second promoted incorporation of oxygen functional groups as well as the growth of a titanium dioxide film. In this paper we show that oxygen atoms or oxygen containing groups play an important role in the repulsion of platelets and their deactivation. At the same time, increased surface temperature of samples either through sequential thermal deactivation in oven at 150°C or heating the surface with ion bombardment during the treatment, lowers the oxygen content and the surface repulsion for platelets.
► We investigated repulsion of blood platelets on oxygen plasma functionalized titanium surface used for coronial stents. ► Increased concentration of interstitial oxygen atoms or oxygen polar groups increases repulsion and deactivates platelets. ► Thermal treatment of plasma functionalized surfaces lowers the oxygen content and increases adhesion and activity of platelets.
Sterilization of delicate materials by gaseous plasma represents an interesting task for plasma scientists. While sporulating bacteria are rather resistant to weak plasma treatments, some bacteria ...are destroyed even in an afterglow. A representative type of nonsporulating bacteria is Staphylococcus aureus. Such bacteria are destroyed by treatment with mostly neutral O atoms found in oxygen plasma afterglow. The degradation steps are followed by atomic force microscopy. The bacteria remain vital for about 2 min of treatment at the O flux of about 1.3 ×10 22 m -2 ·s -1 . The bacterial capsule is removed in about 2 min. Once the capsule is removed, degradation of the cell wall occurs, causing bacterial death.
A number of polyvinyl chloride (PVC) applications require a modification of surface properties of the polymer. In the present work, the effects of plasma treatment on the resulting surface, including ...chemical composition, wettability, and roughness, were assessed using X-ray photoelectron spectroscopy, contact angle measurements, and scanning electron microscopy analysis. A significant alteration regarding the oxygen and carbon content as evidenced by the XPS data was observed after oxygen plasma treatment. Scanning electron microscope images revealed a drastic change of the topography of the treated surface. These changes correspond to improvement in the printability of the treated surface. Therefore, plasma modification in air is demonstrated to be a viable method to improve printability of PVC.
Inductively coupled oxygen plasma was used to study degradation of Escherichia coli. Bacteria were deposited on a silicon wafer substrate and treated by plasma for different periods. The effect of ...oxygen plasma ions and neutral oxygen atoms was observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The first effect was removal of the envelope - a protective coating bacteria developed during growing. After removing the envelope (capsule), slow etching of the cell wall was observed. Further treatment resulted in gradual removal of the cell wall and after 240s, only ashes remained. Images of plasma interaction steps during bacteria degradation are presented and the plasma radical interaction steps explained by observed damages of bacteria.
This study investigates the changes in morphology and wettability of amorphous and semicrystalline polyethyleneterephthalate (PET) polymers, which were treated in weakly ionized, highly dissociated ...RF oxygen plasma. The polymers were treated in glow region for different exposure times with the discharge power set to 250 W and the gas pressure set to 75 Pa. Results indicate that plasma modification has different effects on the surface properties of amorphous and semicrystalline polymers. The amorphous polymers are more sensitive to plasma treatment, as they can be quickly burned, while this is not the case for semicrystalline polymers. With the atomic force microscopy (AFM) different surface structures were observed, which become even more pronounced after plasma treatment. The measurements of water contact angle (WCA) on polymer surfaces also revealed different characters. The plasma treatment of amorphous polymer resulted in a lower hydrophilicity than was observed for the semicrystalline polymer at the some conditions.
In this paper, a review of cold plasma setups and the physical and chemical processes leading to the generation of active species is presented. The emphasis is given to the interaction of cold ...plasmas with materials used in medical applications, especially medical implants as well as live cells. An overview of the different kinds of plasmas and techniques used for generation of active species, which significantly alter the surface properties of biomaterials is presented. The elemental processes responsible for the observed changes in the physio-chemical properties of surfaces when exposed to plasma are described. Examples of ongoing research in the field are given to illustrate the state-of-the-art at the more conceptual level.
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