Plasma, surface activation

AFM is often chosen for topological characterization of the modified surface Fig. 1.13 shows the surface graft polymerization of l-vinyl-2-pyrrolidone onto a silicon surface, accomplished by atmospheric pressure hydrogen plasma surface activation, followed by graft polymerization in both A-methyl-2-pyrrolidone (NMP)... 

The reaction mechanisms of plasma polymerization processes are not understood in detail. Poll et al [34] (figure C2.13.6) proposed a possible generic reaction sequence. Plasma-initiated polymerization can lead to the polymerization of a suitable monomer directly at the surface. The reaction is probably triggered by collisions of energetic ions or electrons, energetic photons or interactions of metastables or free radicals produced in the plasma with the surface. Activation processes in the plasma and the film fonnation at the surface may also result in the fonnation of non-reactive products. 

Surface Modification. Plasma surface modification can include surface cleaning, surface activation, heat treatments, and plasma polymerization. Surface cleaning and surface activation are usually performed for enhanced joining of materials (see Metal SURFACE TREATMENTS). Plasma heat treatments are not, however, limited to high temperature equiUbrium plasmas on metals. Heat treatments of organic materials are also possible. Plasma polymerization crosses the boundaries between surface modification and materials production by producing materials often not available by any other method. In many cases these new materials can be appHed directly to a substrate, thus modifying the substrate in a novel way. 

Electric discharge (corona, cold plasma) is another method of physical treatment. Corona treatment is one of the most interesting techniques for surface oxidation activation. This process changes the surface energy of the cellulose fibers [28]. In the case of wood surface activation it increases the amount of aldehyde groups [291. 

One function of HK is to present the substrates of factor Xlla in a conformation that facilitates their activation [25, 26]. More difficult to explain is the effect of HK on the rate of factor XII activation in plasma since HK does not interact with factor XII, nor does it augment the activity of kaiiikrein. This effect seems to be largely indirect. First, HK is required for efficient formation of kaiiikrein in surface-activated plasma [26, 27]. Second, since kaiiikrein can disassociate from surface-bound... 

The formation of Au nanoparticles can be easily monitored by following the appearance of a surface plasma resonance band around 520-540 nm (Fig. 6.1). Yeung et al. [33] observed that the efficiency of gold particle formation was different in different alcohols (n-pentanol > propan-2-ol > methanol). This is due to the air/water surface activity of the alcohols and the ability of the solute to scavenge the primary OH radicals at the bubble/liquid interface. 

Borzelleca JF, OHara TM, Gennings C, et al. 1990. Interactions of water contaminants. I. Plasma enzyme activity and response surface methodology following gavage administration of CC14 and CHC13 or TCE singly and in combination in the rat. Fundam Appl Toxicol 14 477-490. 

To realize surface-bonded initiating sites or their precursors, a variety of methods are applicable. Either organic (polymer) surfaces are irradiated or plasma treated to yield suitable functional groups [187, 195] or inorganic supports are covered with an interlayer of functional polymers bearing the desired groups. However, to gain control over the quantity of surface reaction sites and define the surface chemistry, interlayers of low molar mass a,co-functionalized surface active compounds are suit-... 

Plasma treatment is useful to activate the surface of a certain material. The treatment enhances the adhesion property. Basically, surface activation effects the introduction of chemical functionalities on the polymer surface in order to increase its surface energy. 

In milk, the important interfaces are those between the liquid product and air and between the milk plasma and the fat globules contained therein. Studies of the surface tension (liquid/air) have been made to ascertain the relative effectiveness of the milk components as depressants to follow changes in surface-active components as a result of processing to follow the release of free fatty acids during lipolysis and to attempt to explain the foaming phenomenon so characteristic of milk. Interfacial tensions between milk fat and solutions of milk components have been measured in studies of the stabilization of fat globules in natural and processed milks. 

Determined as follows 1 mg of the copolymer was dispersed in a 0.1 ml solution of non-ionogenic surface-active compound at 37 °C for 10 min 0.2 ml of plasma were added to the suspension the mixture was incubated for 15 min at 37 °C 0.1 ml thrombin (5 U/ml) (thrombin time) or 0.2 ml of 0.025 M CaCl2 (recalcification time) were then added and the time of clot formation was measured. 

We now may examine the relevance of surface tension measurements to interactions of cells in contact with serum or plasma. The surface tensions reported in Table I for the unfiltered liquids are much lower than those of the ultrafiltrates, at least in part, because of the adsorption of proteins having molecular weight > 20,000 at the liquid-air interface. And the measurements made on the ultrafiltrates are likely to be a good approximation to the zero-time surface tensions of the whole serum and plasma. The solutes that remain in the solution after ultrafiltration evidently are of a relatively low level of surface activity, and do not affect the surface tension to any greater extent than would be expected from their volume fractions. 

Finally, we can estimate the comparative influence of plasma and serum proteins with molecular weights > 20,000 on the cell-serum and cell-plasma interfaces, as opposed to surface-active solutes such as ethylene glycol or dimethylsulfoxide (6). The latter will adsorb at the interfaces to an extent that is comparable with their adsorption at the liquid-... 

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