Behavioral Resistance

A prevailing pathophysiologic explanation for ADHD symptoms involves dehcits in prefrontal cortex-mediated executive brain function also known as response inhibition. Children with ADHD are unable to control their behavior, resist distractions, and develop an awareness of space and time. In addition, a dysregulation of arousal in frontosubcortical pathways has been proposed. Children with ADHD display insufhcient alertness dming dull and repetitive tasks, alternating with overarousal. ... 

The wide spectrum of pyrethroid resistance in these populations, which involves permethrin, fenvalerate, flucythrinate, cypermethrin, deltamethrin, and cyhalothrin, the relative lack of synergism by p. b. (52) or DEF, and the presence of DDT as well as methoxychlor resistance (52), suggest that this resistance is due to the site insensitivity mechanism kdr. Interestingly, some evidence of behavioral resistance was also detected. It was observed that pyrethroid-resistant flies tended to... 

Consequently, Eqs. 3 and 4 are the type of relations that should be used when modeling rheology of HPAM solutions in porous rock. In the past, we often noted cases in which commercial and academic simulators incorrectly assumed pseudoplastic behavior for HPAM solutions in porous media. Although HPAM solutions are well known to exhibit pseudoplastic behavior in viscometers, the petroleum literature (Pye 1964 Smith 1970 Jennings et al. 1971 Hirasaki and Pope 1974 Seright 1983) consistently revealed Newtonian or pseudodUatant behavior (resistance factor increases with increased flux) in porous rock (as shown in Fig. 10 for HPAM in 0.3% NaCl and in Fig. 12 for HPAM in seawater). The viscoelastic nature of the HPAM solutions in porous media overwhelms the pseudoplastic behavior seen in a viscometer. This point can be appreciated by examining the circle symbols in Fig. 10. 

In order to characterize the behavior of motor fuels or their components with regard to knocking resistance but without involving chemical composition criteria which are complex and not easy to quantify, the traditional method that has been universally employed for more than 50 years consists of introducing the concept of octane number. 

Two criteria are used to characterize the behavior of diesel fuel in this area these are color and resistance to oxidation. 

Greases Mechanical and rheological behavior and its persistence Consistency and viscosity Mechanical stability Oxidation resistance... 

The impact on negative-CA resists of airborne base contamination differs qualitatively from their positive tone counterparts. Suppression of acid-catalyzed chemistry at the surface of a negative resist results in some film erosion at the top of the exposed fields and in some cases an apparent loss of photosensitivity, but in general the reUef images formed exhibit the expected cross-sectional profile. This is in sharp contrast with the typical behavior seen with positive-tone CA resists, where suppression of acid-catalyzed chemistry at the surface causes an insoluble surface skin. 

In other work, the impact of thermal processing on linewidth variation was examined and interpreted in terms of how the resist s varying viscoelastic properties influence acid diffusion (105). The authors observed two distinct behaviors, above and below the resist film s glass transition. For example, a plot of the rate of deprotection as a function of post-exposure processing temperature show a change in slope very close to the T of the resist. Process latitude was improved and linewidth variation was naininiized when the temperature of post-exposure processing was below the film s T. 

Physical Properties Electrical. Electrical properties have been the main focus of study of organic semiconductors, and conductivity studies on organic materials have led to the development of materials with extremely low resistivities and large anisotropies. A discussion of conductivity behaviors for various classes of compounds follows. 

In packed beds of particles possessing small pores, dilute aqueous solutions of hydroly2ed polyacrylamide will sometimes exhibit dilatant behavior iastead of the usual shear thinning behavior seen ia simple shear or Couette flow. In elongational flow, such as flow through porous sandstone, flow resistance can iacrease with flow rate due to iacreases ia elongational viscosity and normal stress differences. The iacrease ia normal stress differences with shear rate is typical of isotropic polymer solutions. Normal stress differences of anisotropic polymers, such as xanthan ia water, are shear rate iadependent (25,26). 

The resistance to plastic flow can be schematically illustrated by dashpots with characteristic viscosities. The resistance to deformations within the elastic regions can be characterized by elastic springs and spring force constants. In real fibers, in contrast to ideal fibers, the mechanical behavior is best characterized by simultaneous elastic and plastic deformations. Materials that undergo simultaneous elastic and plastic effects are said to be viscoelastic. Several models describing viscoelasticity in terms of springs and dashpots in various series and parallel combinations have been proposed. The concepts of elasticity, plasticity, and viscoelasticity have been the subjects of several excellent reviews (21,22). 

Electrical Behavior. The resistivity of acetate varies significantly with humidity with typical values ranging from 10 ohm-cm at 45% rh to 10 ohm-cm at 95% rh (16). Because of the high resistivity both acetate and triacetate yams readily develop static charges and an antistatic finish is usually apphed to aid in fiber processing. Both yams have also been used for electrical insulation after lubricants and other finishing agents are removed. 

The medium resistance R, which theoretically should be constant, often varies with time. This behavior results when some of the soHds penetrate the medium or when it compresses under appHed pressure. For convenience, the resistance of the piping and the feed and outlet ports is sometimes included in R. 

Conventional filtration theory has been challenged a two-phase theory has been appHed to filtration and used to explain the deviations from paraboHc behavior in the initial stages of the filtration process (10). This new theory incorporates the medium as an integral part of the process and shows that the interaction of the cake particles with the medium controls filterabiHty. It defines a cake-septum permeabiHty which then appears in the slope of the conventional plots instead of the cake resistance. This theory, which merely represents a new way of interpreting test data rather than a new method of siting or scaling filters, is not yet accepted by the engineering community. 

Fluidization refers to the condition in which soHd materials are given free-flowing, fluid-like behavior (29). As a gas is passed upward through a bed of sohd particles, the flow of gas produces forces which tend to separate the particles from one another. At low gas flows, the particles remain in contact with other soflds and tend to resist movement. This condition is referred to as a fixed bed. As the gas flow is increased, a point is reached at which the forces on the particles are just sufficient to cause separation. The bed then becomes fluidized. The gas cushion between the soflds allows the particles to move freely, giving the bed a Hquid-like characteristic. 

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