Intrinsic resistance

Microbial Resistance to Drugs. Figure 1 MlC-distribution showing the number of isolates of one species with a certain MIC. Some bacterial species are naturally resistant (intrinsic resistance) to drugs because their natural MIC is above the breakpoint. Naturally sensitive isolates as well as naturally resistant ones can acquire resistance and with that increase their MIC (acquired or secondary resistance). 

Gray cubic crystal density 5.316 g/cm melts at 1,227°C hardness 4.5 Mohs lattice constant 5.653A dielectric constant 11.1 resistivity (intrinsic) at 27°C, 3.7x10 ohm-cm. 

The safety-related parameters U, I, P, C and L can be matched to the corresponding values of the relevant intrinsically safe apparatus (sensors, actuators etc.) by variations of rated voltage and series resistance. Intrinsic safety may be engineered in a very flexible way using safety barriers. After all, even hopeless cases may be put into practice frequently. Additional advice for engineering is given in Section 6.9.5. 

MECHANISMS OF INTRINSIC RESISTANCE (INTRINSIC INSUSCEPTIBILITY) 137 Intrinsic resistance in Gram-negative bacteria 137... 

MECHANISMS OF RESISTANCE Intrinsic resistance Exclusion EDTA studies Crypticity studies... 

In this complex sequence of events the most important rate is the intrinsic rate of reaction which is composed of three rates the rate of surface reaction, the rate of chemisorption and the rate of desorption. The three processes are called the intrinsic kinetics i.e. the rate of reaction in the absence of any mass or heat transfer resistances. Intrinsic kinetics is almost always predicted experimentally in differential or integral laboratory reactors using fine powders to avoid diffusional resistances. This is not an easy task especially with regard to temperature gradients for highly exothermic reactions. Experimental difficulties associated with the development of models for intrinsic kinetics are not discussed in this book. However, the kinetic modelling of the intrinsic rates is described in chapter 3. 

Antibiotics have been used for the treatment of bacterial infections for more than 50 years. However, since that time, we have learned that antibiotics did not kill certain bacteria. It is generally accepted that there are two major classes of antibiotic resistance intrinsic resistance and acquired resistance. 

To investigate whether there was any molecular modification of the PSII reaction centre of the R2K1 mutant that made it more resistant intrinsically to photoinhibition we performed photoinhibition experiments in the presence of streptomycin to inhibit all recovery from photoinhibition. The increase of susceptibility to photoinhibition was observed and all three strains showed similar sensitivities (data not shown). 

Two major types of microbial resistance can be distinguished intrinsic and acquired resistance. Intrinsic (innate) resistance refers to a natural chromosomally controlled property, including physiological adaptation. 

Figure C2.16.1. A nomogram comparing electrical resistivity of pure (intrinsic) and doped Si witli metals and insulators.

This concludes our discussion of the viscosity of polymer solutions per se, although various aspects of the viscous resistance to particle motion continue to appear in the remainder of the chapter. We began this chapter by discussing the intrinsic viscosity and the friction factor for rigid spheres. Now that we have developed the intrinsic viscosity well beyond that first introduction, we shall do the same (more or less) for the friction factor. We turn to this in the next section, considering the relationship between the friction factor and diffusion. 

Poly(vinyl cinnamate) Resists. Dichromated resists exhibit numerous shortcomings which include lot-to-lot variabiUty of the components, aging of the formulated resists in solution and in coated form, poor process stabiUty (due to a sensitivity to variations in temperature and humidity), and intrinsically low photosensitivity requiring long exposure times for adequate insolubilization. 

As PWB technology is refined to provide greater integration using finer conductor lines, there is renewed interest in hquid resists. The absence of a cover sheet and the abihty to apply thinner films both contribute to improved resolution and to an intrinsically lower consumables cost (16,17). 

Positive-Tone Photoresists based on Dissolution Inhibition by Diazonaphthoquinones. The intrinsic limitations of bis-azide—cycHzed mbber resist systems led the semiconductor industry to shift to a class of imaging materials based on diazonaphthoquinone (DNQ) photosensitizers. Both the chemistry and the imaging mechanism of these resists (Fig. 10) differ in fundamental ways from those described thus far (23). The DNQ acts as a dissolution inhibitor for the matrix resin, a low molecular weight condensation product of formaldehyde and cresol isomers known as novolac (24). The phenoHc stmcture renders the novolac polymer weakly acidic, and readily soluble in aqueous alkaline solutions. In admixture with an appropriate DNQ the polymer s dissolution rate is sharply decreased. Photolysis causes the DNQ to undergo a multistep reaction sequence, ultimately forming a base-soluble carboxyHc acid which does not inhibit film dissolution. Immersion of a pattemwise-exposed film of the resist in an aqueous solution of hydroxide ion leads to rapid dissolution of the exposed areas and only very slow dissolution of unexposed regions. In contrast with crosslinking resists, the film solubiHty is controUed by chemical and polarity differences rather than molecular size. 

The polymers dissolve in l,l,l,3,3,3-hexafluoro-2-propanol [920-66-1/, hot phenols, and /V, /V- dim ethyl form am i de [68-12-2] near its boiling point. The excellent solvent resistance notwithstanding, solvents suitable for measurement of intrinsic viscosity, useflil for estimation of molecular weight, are known (13,15). 

SAN resins show considerable resistance to solvents and are insoluble in carbon tetrachloride, ethyl alcohol, gasoline, and hydrocarbon solvents. They are swelled by solvents such as ben2ene, ether, and toluene. Polar solvents such as acetone, chloroform, dioxane, methyl ethyl ketone, and pyridine will dissolve SAN (14). The interactions of various solvents and SAN copolymers containing up to 52% acrylonitrile have been studied along with their thermodynamic parameters, ie, the second virial coefficient, free-energy parameter, expansion factor, and intrinsic viscosity (15). 

In contrast, physical adsorption is a very rapid process, so the rate is always controlled by mass transfer resistance rather than by the intrinsic adsorption kinetics. However, under certain conditions the combination of a diffiision-controUed process with an adsorption equiUbrium constant that varies according to equation 1 can give the appearance of activated adsorption. 

AH intrinsic germanium metal sold is specified to be N-type with a resistivity of at least 40 H-cm at 25°C or 50 H-cm at 20°C. Germanium metal prepared for use in infrared optics is usuaHy specified to be N-type with a resistivity of 4-40 Hem, to be stress-free and fine annealed, and to have certain minimum transmission (or maximum absorption) characteristics in the 3—5 or 8—12 pm wavelength ranges. Either polycrystaHine or single-crystal material is specified. 

Fabric Composition. The method of fabric manufacture dictates many of the characteristics of the sheet, but intrinsic properties are firmly estabhshed by the base polymer selected. Properties such as fiber density, temperature resistance, chemical and light stabiUty, ease of coloration, surface energies, and others are a function of the base polymer. Thus, because nylon absorbs more moisture than polypropylene, spunbonded fabrics made from nylon are more water absorbent than fabrics of polypropylene. 

Intrinsic asthma, also called idiopathic asthma, usually develops in adulthood. In intrinsic asthma allergic factors are not demonstrable. Episodes of intrinsic asthma may be triggered by a variety of stimuli, eg, emotional state, exposure to cold air, or inert dusts. Both intrinsic and extrinsic asthmatics can be prone to exercise-induced attacks. Individuals who experience a combination of extrinsic and intrinsic asthmatic reactions have mixed asthma. Status asthmaticus refers to an especially acute life-threatening asthma attack which is resistant to normal treatments and which may require hospitalization in order to stabilize the patient. 

To achieve the lowest possible delay a bipolar switching transistor developed by IBM minimizes parasitic resistances and capacitances. It consists of self-aligned emitter and base contacts, a thin intrinsic base with an optimized collector doping profile, and deep-trench isolation (36). Devices must be isolated from each other to prevent unwanted interactions in integrated circuits. While p—n junctions can be used for isolation, IBM s approach etches deep trenches in the siUcon wafer which are filled with Si02 to provide electrical insulation. 

---