Nature of resistance

Abstract The entry of viruses into target cells involves a complex series of sequential steps, with opportunities for inhibition at every stage. Entry inhibitors exert their biological properties by inhibiting protein-protein interactions either within the viral envelope (Env) glycoproteins or between viral Env and host-cell receptors. The nature of resistance to entry inhibitors also differs from compounds inhibiting enzymatic targets due to their different modes of action and the relative variability in... 

Putwain, P.D., K.R. Scott, and R.J. Holliday (1982). The nature of resistance to triazine herbicides Case histories of phenology and population studies. In H.M. LeBaron and J. Gressel, eds., Herbicide Resistance in Plants. NY, NY John Wiley Sons, pp. 99-115. 

Resistance Although the true nature of resistance to nitrosoureas is unknown, it probably results from DNA repair and reaction of the drugs with thiols. 

To create the means — and indeed, the will — to combat resistance, one must first understand it. Though the details of each specific situation are complex, the general nature of resistance can be understood in terms of genetics and natural selection. 

In view of the evolutionary nature of resistance, additional cases are bound to arise as new insecticides are being introduced and selection pressure remains high. Figure 1, based on a data bank that we are maintaining for the Food and Agriculture Organization of the United Nations (FAO), indicates the progressive increase in the number of species of insects and mites world-wide, that have developed resistance to one or more insecticides. 

More extensive investigations and comparable data are required for the knowledge of the nature of resistance of lichens to irradiation. In general, lichens accumulate a higher level of radioactive nuclides than vascular plants and are far more radioresistant. This can be illustrated by comparing the... 

The friermal decohesion model for impact and dynamic fracture in thermoplastics asserts that fracture resistance is not constant, and is strongly supported by experimental data. It also emphasises that the nature of resistance to impact britfle fracture is profoundly different from that to other brittle fracture modes. The model can be used, however, to construct an alternative scheme for transferring data between impact configurations. This scheme has been demonstrated for a practical impact failure problem. 

The derivatives are hydroxyethyl and hydroxypropyl cellulose. AH four derivatives find numerous appHcations and there are other reactants that can be added to ceUulose, including the mixed addition of reactants lea ding to adducts of commercial significance. In the commercial production of mixed ethers there are economic factors to consider that include the efficiency of adduct additions (ca 40%), waste product disposal, and the method of product recovery and drying on a commercial scale. The products produced by equation 2 require heat and produce NaCl, a corrosive by-product, with each mole of adduct added. These products are produced by a paste process and require corrosion-resistant production units. The oxirane additions (eq. 3) are exothermic, and with the explosive nature of the oxiranes, require a dispersion diluent in their synthesis (see Cellulose ethers). 

The magnitude and nature of the load are considered in formulating the design. The load may be essentially quasistatic, cycHc, or impact. Many stmctural failures, for example, have been caused by supposedly innocuous stmctural details welded in place without any consideration given to their effect on fatigue properties. The service temperatures are also important, since they affect the fracture resistance of a material. 

Flame-Retardant Treatments For Wool. Although wool is regarded as a naturally flame-resistant fiber, for certain appHcations, such as use in aircraft, it is necessary to meet more stringent requirements. The Zirpro process, developed for this purpose (122,123), is based on the exhaustion of negatively charged zirconium and titanium complexes on wool fiber under acidic conditions. Specific agents used for this purpose are potassium hexafluoro zirconate [16923-95-8] [16923-95-8] K ZrF, and potassium hexafluoro titanate [16919-27-0], K TiF. Various modifications of this process have been... 

Buoyancy. The low density, closed-ceUed nature of many ceUular polymers coupled with their moisture resistance and low cost resulted in their immediate acceptance for buoyancy in boats and floating stmctures such as docks and buoys. Since each ceU in the foam is a separate flotation member, these materials caimot be destroyed by a single puncture. 

Resistance to antimicrobial agents is of concern as it is well known that bacterial resistance to antibiotics can develop. Many bacteria already derive some nonspecific resistance to biocides through morphological features such as thek cell wall. Bacterial populations present as part of a biofilm have achieved additional resistance owkig to the more complex and thicker nature of the biofilm. A system contaminated with a biofilm population can requke several orders of magnitude more chlorine to achieve control than unassociated bacteria of the same species. A second type of resistance is attributed to chemical deactivation of the biocide. This deactivation resistance to the strong oxidising biocides probably will not occur (27). 

Water. Latices should be made with deionized water or condensate water. The resistivity of the water should be at least lO Q. Long-term storage of water should be avoided to prevent bacteria growth. If the ionic nature of the water is poor, problems of poor latex stabiUty and failed redox systems can occur. Antifreeze additives are added to the water when polymerization below 0°C is required (37). Low temperature polymerization is used to limit polymer branching, thereby increasing crystallinity. 

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