Acid resistance mechanisms

Physiology of Acetobacter and Komagataeibacter spp. Acetic Acid Resistance Mechanism in Acetic Acid Fermentation... 

Other acid resistance mechanisms include urease, a nickel-containing oligomeric enzyme that catalyzes the hydrolysis of urea to two molecules of ammonia and one molecule of carbon dioxide (Mobley et al. 1995). The enzyme has maximal activity at pH 7 but loses activity at more extreme acidic pHs, being essentially inactive at pH 4.3. Ureases have been mostly associated with pathogens with the most studied system encoded by the highly urolytic bacteria Helicobacter pylori (Bartnik... 

Polysulfide 150 Excellent resistance to oils, gasoline, aliphatic and aromatic hydrocarbon solvents. Very good water resistance, good alkali resistance, fair acid resistance. Poor mechanical properties. 

Neoprene 250 Excellent mechanical properties. Good resistance to uouaromatic petroleum, fatty oils, solvents (except aromatic, chlorinated, or ketone types). Good water and alkali resistance. Fair acid resistance. 

Improvement in the solvent and oil resistance of rubbers can be achieved via grafting of acrylonitrile onto rubber [140-142] and rubber blends [143]. The careful control of the degree of grafting allows vulcanized rubber with high-mechanical properties compared with ungrafted vulcanized rubber to be obtained. Also, acid resistance [144] and resistance to microbiological attack [145,146] was improved for cellulose grafted with acrylonitrile, and increases in base resistance were also noted for MMA and a mixture of MMA and ethyl acrylate [13],... 

Using present ideas of glass structure, frits can be formulated to have maximum durability. Zirconia enamels have a lower than optimum acid resistance, but titania enamels have superior durability at low pH values. Encouraging crystallisation in the enamel enhances mechanical strength and therefore chemical resistance by reducing the incidence of damage sites which act as foci for attack. The addition of an extra (clear) coat on to the top most coat of enamel gives superior chemical resistance". 

It is generally true that the lower the porosity the higher the mechanical strength and the acid resistance of the body, but unfortunately low porosity also usually results in reduced thermal shock resistance. 

The possible involvement of polygalacturonic acid-containing molecules in the defence reactions of tomato root cells against Fusarium oxysporum was suggested about 20 years ago by their accumulation at penetration sites. Since papillae are held to serve as a resistance mechanism to fungal penetration, it was assumed that the interrelation between pectin and other polymers - such as lignin - may contribute to enhancing the hardness of these newly formed structures (Benhamou et al., 1990). 

Fusidic acid, bacterial resistance mechanisms, 3 32t Fusinite, 6 707t, 719, 828 Fusion, PVC, 25 663-664. See also Cold fusion Deuterium fusion Fusion-bonded-epoxies (FBE), 10 440 Fusion carburization, 4 674-675 Fusion-cast refractories, 21 504 shapes of, 21 481-482 Fusion method, for tin content assays, 24 791, 792... 

Linalool, 3 231, 232, 233 24 477, 495, 496, 500-503, 546 acid treatment of, 24 502 epoxidation of, 24 502 main producers of, 24 501 Linalool oxide, 24 502 Linalyl, 24 479 Linalyl acetate, 24 501 Linalyl alcohol, 24 500 Linalyl esters, 3 231 Linalyl oxide, 24 503 Lincomycin, registered for use in aquaculture in Japan, 3 221t Lincosamide, bacterial resistance mechanisms, 3 32t Lindane, 13 145-147... 

The sample introduction unit was constructed from inert materials, which minimizes the introduction of metal contamination into the system. The samples or digestion acids make contact only with PTFE, Kel-F, glass, acid-resistant rubber and platinum-iridium (9 + 1) alloy. In addition, the construction materials were Hmited to acid-grade Arborite (ureaformaldehyde laminate). Perspex and stainless-steel. The unit was constructed in three continuous sections a heated sample compartment, a turntable mechanism and heat-exchanger compartment, and a pump compartment. 

B. Overproduction (A) of PABA is one of the resistance mechanisms of sulfonamides. Changes in the synthesis of DNA gyrases (B) is a well-described mechanism for quinolone resistance. Plasmid-mediated resistance (C) does not occur with quinolones. An active efflux system for transport of drug out of the cell has been described for quinolone resistance, but it is not plasmid mediated. Inhibition of structural blocks (D) in bacterial cell wall synthesis is a basic mechanism of action of p-lactam antibiotics. Inhibition of folic acid synthesis (E) by blocking different steps is the basic mechanism of action of sulfonamides. 

The most common mechanism of isoniazid resistance is the mycobacteria s formation of mutations in catalase-peroxidase KatG, the enzyme that is responsible for activation of isoniazid. Another resistance mechanism is through a missense mutation related to the inhA gene involved in mycolic acid biosynthesis. 

Onium salts have been widely used as an acid generator for photo-, EB, and x-ray resist. In addition, aromatic polymers such as novolak and polyhydroxystyrene have been often used as a base polymer for EB and x-ray resist. The reaction mechanisms in a typical resist system have been investigated by pulse radiolysis [43,52,77-88], SR exposure [79,80,83-85], and product analysis [88]. Figure 6 shows the acid-generation mechanisms induced by ionizing radiation in triphenylsulfonium triflate solution in acetonitrile. The yields of products from electron beam and KrF excimer laser irradiation of 10 mM triphenylsulfonium triflate solution in acetonitrile are shown in Fig. 7 to clarify the... 

Here too there is an enol that tautomerizes to the product. The mechanism is illustrated for the case of p-keto acids,475 but it is likely that malonic acids, a-cyano acids, a-nitro acids, and p,y-unsaturated acids476 behave similarly, since similar six-membered transition states can be written for them. Some a,p-unsaturated acids are also decarboxylated by this mechanism by isomerizing to the p,7-isomers before they actually decarboxylate.477 Evidence is that 36 and similar bicyclic p-keto acids resist decarboxylation.47" In such compounds the... 

The continuous method of nitroglycerine manufacture invented by A. Schmid [38] involves not only continuous nitration, but also continuous separation and washing of the product. A novel idea introduced by Schmid was the nitrator made of acid-resistant steel with mechanical stirring (Fig. 38). 

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