Conditioning films

Microbial cells transported with the stream of fluid above the surface interact with conditioning films. Immediately after attachment, microorganisms initiate production of slimy adhesive substances, predominantly exopolysaccharides (EPS) that assist the formation of microcolonies and microbial films. EPS create bridges for microbial cells to the substratum and permit negatively charged bacteria to adhere to both negatively and positively charged surfaces. EPS may also control interfacial chemistry at the mineral/biofilm interface. 

From the foregoing, it seems likely that apart from a small number of specialist medical applications, the efficacy of surface coated devices may be compromised by antibiotic-resistant bacteria, together with the barrier effect provided by conditioning films that will rapidly coat biomaterials in situ.43... 

These differences in film morphology were also reflected as differences in film formation conditions, film adhesion, and in electrochemical properties. The pyrazoline beads readily formed films from solvents such as benzene. For the phenoxy TTF system, however, only CH2Cl2 was effective in forming films. In general, the TTF cross-linked polymers were found to be less adherent to the metallized substrates than the pyrazoline cross-linked polymers. Electro-chemically, it was found that the pyrazoline films showed complete activity after one potential sweep. The TTF polymer films, on the other hand, required from 5 to 20 cycles to reach full electrochemical activity as evidenced by a constant voltammogram with cycling. Furthermore, it was observed that the TTF polymer films were much less electroactive than the pyrazoline materials as shown by optical densities and total coulombs passed which were several times less for the TTF systems. 

A variety of techniques have been used in the present work to establish the relative sensitivity of positive electron-beam resists made from copolymers of maleic anhydride (Table I). The term sensitivity is used rather loosely at times. In the most practical sense, sensitivity is a comparative measure of the speed with which an exposure can be made. Thus, the exposure conditions, film thickness, developing solvent and temperature may be involved. Most often, the contrast curve is invoked as a more-or-less objective measure of sensitivity. The dose needed to allow removal of exposed film without removing more than about 70% of the unexposed film can be a measure of sensitivity. The initial film thickness and the developing conditions still must be specified so that this measure is not, strictly speaking, an intrinsic property of the polymeric material. 

The polycarbonate films containing the additives were completely transparent, and x-ray diffractometric curves gave no indication of crystallinity. Films with a thickness of about 2 mils could be tightly creased without cracking, but 3- to 4-mil films often cracked under these conditions. Film properties of the polymers from bisphenols I and II and from bisphenol A are listed in Tables I to III, respectively. Some conventional plasticizers also are listed at the bottoms of the tables to show their effect on the film properties. 

Development of a conditioning film. This process should depend on surface properties of the substratum and on the charge and polarity of the sorbed matter. It is a relatively fast [half-saturation times of 5-72 s (Armstrong... 

Alginic Acid Adsorption in the Presence of a Protein Conditioning Film... 

Schneider, R.P., Conditioning-film induced modification of substratum physicochemistry — an analysis by contact angles, J. Colloid Interface Sci., 182, 204, 1996. 

The two methanation reactions are strongly exothermic. The temperature rise for typical methanator gas compositions in hydrogen plants is about 74°C (133°F) for each 1% of carbon monoxide converted and 60°C (108°F) for each 1% of carbon dioxide converted. At higher temperatures, the intrinsic rates of both methanation reactions can become sufficiently fast for diffusion effects to become important as shown in Figure 5.42. Under these conditions, film diffusion controls the overall rate of reaction. Diffusion limitations can be overcome to some extent by using a catalyst with a smaller particle size (3.1mm diameter by 3.6 mm long compared to regular catalyst dimensions of 5.4 mm by... 

Formation of a conditioning film of adsorbed macro-molecular organic components (i.e. proteins and other organic molecules) on the substratum surface prior to microbial deposition. 

Upon approach, organisms will be attracted or repelled by the biomaterial surface, depending on the resultant of the various interaction forces. Thus, the physico-chemical surface properties of the biomaterial, with or without conditioning film, and those of the microorganisms play a decisive role in this process. Because the size of microorganisms is in the im range, adhesion can be described in terms of colloid science. Indeed, for several strains and species physico-chemical models like the Deijaguin-... 

Delivery temperatures of 264 °C and 350 °C were used to give films 1 and 2, respectively. In the formation of film 2 with a delivery temperature of 350 °C, premature precursor decomposition was observed in the delivery zone. Deposition temperature was also found to be a very important factor. The deposition at 300 °C gave a much thinner film. Films 1 and 2 deposited at 448-450 °C had a gold color and a dark blue black zone, reflecting some bluish gray light. Under the same conditions, films deposited on quartz substrates below 450 °C had very different appearances compared to those grown on a Si(lOO) wafer. They were very thin, transparent and quite yellow. 

Some of the areas where interfacial protein layers dominate the boundary chemistry are reviewed, and we introduce some nondestructive armlytical methods which can be used simultaneously and/or sequentially to detect and characterize the microscopic amounts of matter at protein or other substrates which spontaneously acquire protein conditioning films. Examples include collagen and gelatin, synthetic polypeptides, nylons, and the biomedically important surfaces of vessel grafts, skin, tissue, and blood. The importance of prerequisite adsorbed films of proteins during thrombus formation, cell adhesion, use of intrauterine contraceptives, development of dental adhesives, and prevention of maritime fouling is discussed. Specifics of protein adsorption at solid/liquid and gas/liquid interfaces are compared. 

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