Biological deposit

Biofilms can promote corrosion of fouled metal surfaces in a variety of ways. This is referred to as microbiaHy influenced corrosion. Microbes act as biological catalysts promoting conventional corrosion mechanisms the simple, passive presence of the biological deposit prevents corrosion inhibitors from reaching and passivating the fouled surface microbial reactions can accelerate ongoing corrosion reactions and microbial by-products can be directly aggressive to the metal. 

Sorby (1879) put forth one of the earliest non-biological hypotheses for the mechanism of odid formation. His basic idea was that odids with a concentric structure form by a process similar to that which forms a snowball. In his model, an organic coating is biologically deposited (the infamous "mucilagenous slime") on... 

There is macroporous silica diatomite or diatomeceous earth as biological deposits of sea algae diatom . This is used as an industrial filter aid and heat insulator. The inside space of the bamboo stems and the rice straws contain silicas of high purity. 

Batch process stop feed because the membrane performance has deteriorated or because the target concentrations or volumes of permeate or retentate have been achieved. Deteriorated membrane performance can be (1) because of a buildup of particulates or biological deposits (this can be corrected by backflushing with permeate or cleaning with detergents, acids, or bases) or (2) because the membrane needs to be replaced (the life of a membrane is one or two to ten years, depending on the operating conditions and the type of membrane). See Table 16.32. 

Oils or light greases (a) Sodium hydroxide, carbonate or tri sodium phosphate with or without detergents or (b) Solvent - water emulsions, e.g. kerosene - water Alkalis are also used for the removal of biological deposits Useful for non-ferrous systems which may be attacked by alkalis... 

Dy are biologically deposited in the bones of chinook salmon fingerlings. Hori (406,407,408) has used activation analysis to measure the Na and K content of unfertilized and fertilized eggs of sea-urchins. Barnacle shells have been examined for their Ca, Mg, Sr, and Na contents by Gordon and Larson (337), and Wakita and Kigoshi (978) have found thorium in various Japanese shellfish. Studies on trace element physiology in fresh water snails and mollusks have been reported respectively by Girardi and Merlini (331) and Spronk (903). 

Hardness deposits Poor pH control Biological deposits Insufficient chlorine addition Routine tabulation of heat-transfer coefficients Review vendor s treatment program... 

Crevice corrosion also develops under deposits or fouling, e.g. under the basalt plates of barnacles. The microbiological slime often observed on the surface of stainless steels can shift the free corrosion potential in the positive direction so that the pitting potential of the steels is exceeded [108]. Pipes made of a chromium steel with 26% Cr and 1% Mo failed within a brief period with biological deposits, but remained resistant in deaerated and sterile seawater in desalination plants [109]. 

One of the standard FilmTec products (FT-30) is based on the interfacial polymerization of m-phenylenediamine chain extended and cross-linked with trimesoyl chloride. Sulfonated polysulfone and sulfonated poly(ether sulfone) have also been utilized, as they offer the advantage of chlorine resistance (which is desirable, as chlorine is often employed to remove biological deposits causing membrane fouling). Newer versions of sulfonated polysulfones demonstrating excellent chlorine resistance have recently been reported in the literature. Reverse osmosis is also relevant for organic mixture separations, of which a few have been commercialized such as solvent recovery from lube oil. ... 

Weathering and transportation is followed by the sedimentation of material. The depositional environment can be defined as an area with a typical set of physical, chemical and biological processes which result in a specific type of rock. The characteristics of the resulting sediment package are dependent on the intensity and duration of these processes. The physical, chemical, biological and geomorphic variables... 

A belief that solid interfaces are easier to understand than liquid ones shifted emphasis to the former but the subjects are not really separable, and the advances in the one are giving impetus to the other. There is increasing interest in films of biological and of liquid crystalline materials because of the importance of thin films in microcircuitry (computer chips ), there has been in recent years a surge of activity in the study of deposited mono- and multilayers. These Langmuir-Blodgett films are discussed in Section XV-7. 

Corrosion associated with the action of micro-organisms present in the corrosion system. The biological action of organisms which is responsible for the enliancement of corrosion can be, for instance, to produce aggressive metabolites to render the environment corrosive, or they may be able to participate directly in the electrochemical reactions. In many cases microbial corrosion is closely associated with biofouling, which is caused by the activity of organisms that produce deposits on the metal surface. 

The fir.-fit line of the file (see Figure 2-110) - the HEADER record - hold.s the moleculc. s classification string (columns 11-50), the deposition date (the date when the data were received by the PDB) in columns 51-59, and the PDB (Dcode for the molecule, which is unique within the Protein Data Bank, in columns 63-66. The second line - the TITLE record - contains the title of the experiment or the analysis that is represented in the entry. The subsequent records contain a more detailed description of the macromolecular content of the entiy (COMPND), the biological and/or chemical source ofeach biological molecule in the entiy (SOURCE), a set ofkeywords relevant to the entiy (KEYWDS). information about the experiment (EXPDTA), a list of people responsible for the contents of this entiy (.AUTHOR), a history of modifications made to this entiy since its release (REVDAT), and finally the primaiy literature citation that describes the experiment which resulted in the deposited dataset ()RNL). 

Aragonite. Calcium carbonate is a common deposit in shallow tropical waters as a constituent of muds, or in the upper part of coral reefs where it precipitates from carbon dioxide-rich waters supersaturated with carbonate from intense biological photosynthesis and solar heating. Deposits of ooHtic aragonite, CaCO, extending over 250,000 km in water less than 5 m deep ate mined for industrial purposes in the Bahamas for export to the United States (19). 

Radiation Dosimetry. Radioactive materials cause damage to tissue by the deposition of energy via their radioactive emissions. Thus, when they are internally deposited, all emissions are important. When external, only those emissions that are capable of penetrating the outer layer of skin pose an exposure threat. The biological effects of radiation exposure and dose are generally credited to the formation of free radicals in tissue as a result of the ionization produced (17). 

Subgroup on Metals of the Tri-Academj Committee on Acid Deposition, Acid Deposition Effects on Geochemical Cjcling and Biological Availability of Trace Elements, National Academy Press, Washington, D.C., 1985. 

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