Adherence phenomena

D. Maugis, Overview of adherence phenomena, in Adhesive Chemistry—Developments and Trends (L. H. Lee, ed.), p. 63, Plenum Press, New Yoik (1984) Adherence and fracture mechanics, in Adhesive Bonding (L. H. Lee, ed.). Chapter 10, Plenum Press, New York (1990). 

A. Frumkin, About wetting and adherence phenomena, J. Phys. Chem. USSR, 12, 337 [1938],... 

When gaseous or liquid molecules adhere to thesurface of the adsorbent by means of a chemical reaction and the formation of chemical bonds, the phenomenon is called chemical adsorption or chemisorption. Heat releases of 10 to 100 kcal/g-mol are typical for chemisorption, which are much higher than the heat release for physisorption. With chemical adsorption, regeneration is often either difficult or impossible. Chemisorption usually occurs only at temperatures greater than 200 C when the activation energy is available to make or break chemical bonds. 

The time dependent him is also related to the running history as shown in Fig. 32. Before the system starts running, the static Him is 5 nm thick, /yter 60 minutes of running at a speed of 3.12 mm/s, the system stops running for 10 minutes, and the him drops down to 9 nm. When the system restarts running, the him rapidly recovers. This phenomenon indicates the hlms on the surface of substrates will adhere to the surface for a period of time when the rolling action has stopped, and the him thickness can pick up its value quickly once the rolling is restarted. 

Recently a phenomenon of resistance to biocide solutions has been recognized (see also Chapters 9 and 13) in which bacteria adhere to a container wall and cover themselves with a carbohydrate slime called a glycocalyx thus, doubly protected (wall and glycocalyx), they have been found to resist biocide attack. 

NK cells possess a receptor for Fc/and this enables them to adhere to target cells coated in antibody with the resultant destruction ofthat cell. This phenomenon is known as antibody-dependent cell-mediated cytotoxicity (ADCC). This was attributed to a separate cell population known as killer (K) cells but these have now been shown to be in effect NK cells. 

Inflammatory cell phenomenon are also contributors to lipid peroxidation. Activated neutrophils may adhere to damaged endothelium and amplify traumatic, ischaemic or ischaemia-reperfiision injury. Many cyclooxygenase products of the metabolism of atachidonic acid modulate the inflammatory responses of cells. Macrophages, neutrophils and microglia are important sources of reactive oxygen at the injury site. When activated, they produce a respiratory burst that is traced to activated nicotinamide adenine dinucleotide (NADPH/NADH) oxidase. 

The baking process, particularly the batch variety, presents a number of serious disadvantages. Not only does the reaction produce solid urea decomposition products, but it also releases large amounts of ammonia and ammonium salts which escape by sublimation. The foam which is thus formed makes for a porous reaction mixture, which in turn even prevents heat conduction. Moreover, the reaction mixture tends to adhere to the surface of the reaction vessel and the stirring unit a phenomenon which adds to the complexity of the problem. 

In a more restrictive sense, the term "ion exchange" is used to characterize the replacement of one adsorbed, readily exchangeable ion by another. This circumscription, used in soil science (Sposito, 1989), implies a surface phenomenon involving charged species in outer-sphere complexes or in the diffuse ion swarm. It is not possible to adhere rigorously to this conceptualization because the distinction between inner-sphere and outer-sphere complexation is characterized by a continuous transition, (e.g., H+ binding to humus). 

The term bioadhesion ean be defined as the ability of a material (synthetic or natural) to stick (adhere) to a biological tissue for extended periods of time [27]. The phenomenon of bioadhesion can be visualized as a two-step process. The first step involves the initial contaet between polymer and the biological tissue. The second step is the formation of seeondary bonds due to noncovalent interactions. The strength of bioadhesion (expressed as the foree of detachment) for a novel oligosaccharide gum Hakea Gibbosa) contained in a buccal tablet developed by Alur et al. [28,29]... 

Yeast flocculation mechanism can be described as a phenomenon of adhesion to certain surfaces. The ability to adhere to surfaces and to form biofilm is the basis of the pathogenicity of Candida species. Pathogens adhere to mucous membranes and wounds, they stick to medical instruments and prosthesis, and thus contaminate surfaces in food processing facilities. The high mortality rate in disseminated fungal infections caused an increase in the amount of research on the molecular basis of the adhesive phenomena in Candida. This research discovered a considerable overlap in the molecular regulation of all forms of adhesive behavior. ... 

Evidence of attachment of an organic molecule to a metal surface by a particular group in the molecule is not only provided from surface tension data on the surface of liquid mercury but is also to be noted in the phenomenon of displacement of one liquid by another from a surface. The hydrocarbons adhere to metals much less tenaciously than molecules containing polar groups such as —COOH and —OH. Thus we find that a hydrocarbon may be removed from a metal surface by displacement with alcohol and also that the lubricating properties of a hydrocarbon are materially affected by the addition of hydrocarbon compounds containing polar groups (Hardy, Proc. Roy. 8oc. A, c. 650, 1922, A, ci. 487, 1923). 

Thereafter, the dynamic mixing behaviors of fine cohesive particles adhered to the surface of a coarser excipient was discussed as considerable importance in the manufacture of solid pharmaceuticals (3). The term ordered mixing was given to this phenomenon by Hersey (4). An ordered mixture can be produced by a dry process, simple dry mixing of fine and coarse particles. When interparticle interactions, such as van der Waals and coulombic forces, exist between the two types of particles, the fine particle adheres to the surface of the coarse particle that is, an ordered mixture spontaneously forms. As described earlier, ordered mixing... 

Thermoplasticity of lactose. Unless certain precautions are taken during the drying of whey or other solutions containing high concentrations of lactose, the hot, semi-dry powder may adhere to the metal surfaces of the dryer, forming deposits. This phenomenon is referred to as thermoplasticity. The principal factors influencing the temperature at which thermoplasticity occurs ( sticking temperature ) are the concentrations of lactic acid, amorphous lactose and moisture in the whey powder. 

In the Encyclopedia of Twentieth Century Physics, R.W. Cahn describes A.H. Cottrell and B.A. Bilby s result that strain aging in an interstitial solid solution increases with time as t2/3 as the coming of age of the science of quantitative metallurgy [25]. Strain aging is a phenomenon that occurs when interstitial atoms diffuse to dislocations in a material and adhere to their cores and cause them to be immobilized. Especially remarkable is that the t2/3 relation was derived even before dislocations had been observed. 

Various theories have been postulated to explain the phenomenon that magnetic fields can change the way in which calcium carbonate precipitates and crystallizes, the most probable one being that the applied field distorts the electrical charge carried by small particles of the calcium carbonate already formed in the water, affecting the way in which they adhere to form large particles. 

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