Curves response

Ideally, dose-response curves follow simple relations they are either linear (Fig. 2) or else follow a two-hit kinetics function. Such situations can be found at lower dose ranges, but at higher doses curves can plateau or even decline. Extensive investigation of dose-response relationships with chemically induced mutation has been reported by Heslot i ) nd Schwaier and by Kplmark in Neurospora. 

Studies of variations in temperature and pVi on mutation induction are sometimes difficult, because the shape of dose-response curves can vary considerably (see Schwaier )), At any rate, if effects of j H, temperature, or other factors on the genetic activity of a certain agent are to be investigated, this cannot be done using just one standard dose rather, an entire dose-response curve has to be established in order to arrive at reasonable conclusions. Westergaard has used the optimal dose, the dose which gives the highest mutation frequency, as a basis of comparison. 

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It can be observed from the Figure 1 that the sensitivity of I.I. system is quite low at lower thicknesses and improves as the thicknesses increase. Further the sensitivity is low in case of as observed images compared to processed images. This can be attributed to the quantum fluctuations in the number of photons received and also to the electronic and screen noise. Integration of the images reduces this noise by a factor of N where N is the number of frames. Another observation of interest from the experiment was that if the orientation of the wires was horizontal there was a decrease in the observed sensitivity. It can be observed from the contrast response curves that the response for defect detection is better in magnified modes compared to normal mode of the II tube. Further, it can be observed that the vertical resolution is better compared to horizontal which is in line with prediction by the sensitivity curves. 

Modem NDT film systems (with Pb screens) are very linear X-ray detectors. This is shown in fig.l for different NDT film systems and a X-ray tube at 160 kV. Note that for histoncal reasons the film response curve is often plotted as film density versus log (radiation dose), which hides this linear relationship. The film density is the difference between the measured optical film density and the fog density Db of the film base. 

Fig.l Film response curves of several NDT film systems (160 kV X-ray tube)... 

The sharpness of the frequency response of a resonant system is conunonly described by a factor of merit, called the quality factor, Q=v/Av. It may be obtained from a measurement of the frill width at half maxuuum Av, of the resonator frequency response curve obtained from a frequency sweep covering the resonance. The sensitivity of a system (proportional to the inverse of tlie minimum detectable number of paramagnetic centres in an EPR cavity) critically depends on the quality factor... 

Two different types of dynamic test have been devised to exploit this possibility. The first and more easily interpretable, used by Gibilaro et al [62] and by Dogu and Smith [63], employs a cell geometrically similar to the Wicke-Kallenbach apparatus, with a flow of carrier gas past each face of the porous septum. A sharp pulse of tracer is injected into the carrier stream on one side, and the response of the gas stream composition on the other side is then monitored as a function of time. Interpretation is based on the first two moments of the measured response curve, and Gibilaro et al refer explicitly to a model of the medium with a blmodal pore... 

Blending behavior of a binary mixture may be characterized by a linear blending value (LBV). Figure 4 shows the response curve of a hypothetical two-component mixture. The LBV for each of the components at any composition is defined by the tangent at that point according to the formula. 

Fig. 4. Octane blending behavior where (--) represents the measured octane response curve, (-) the tangent to the curve, and (-) the linear...

The advantage of this definition is that it does not depend on measuting the tangent of the response curve, although the variation ia the value of the blending octane number is greater. Typically, BONs are measured at an 80/20 mixture. This technique is also usehil when trying to measure the octane of a compound such as butane or methanol that is difficult or impossible to measure ia its pure state. 

Pig. 11. Luminous performance vs peak emission wavelength for the best reported high brightness LEDs. Some high performance lighting sources are indicated. The numbers in parentheses correspond to the source wattage. Also shown is the (—) eye response curve (as defined by the Commission... 

Dmg distribution into tissue reservoirs depends on the physicochemical properties of the dmg. Tissue reservoirs include fat, bone, and the principal body organs. Access of dmgs to these reservoirs depends on partition coefficient, charge or degree of ionization at physiological pH, and extent of protein binding. Thus, lipophilic molecules accumulate in fat reservoirs and this accumulation can alter considerably both the duration and the concentration—response curves of dmg action. Some dmgs may accumulate selectively in defined tissues, for example, the tetracycline antibiotics in bone (see Antibiotics,tetracyclines). 

Fig. 6. Cumulative log concentration-response curves for the homologous-A/-aLkylcatecholamines,...

Fig. 8. Agonist, dose—response curves, (a) For an agonist where a value of 10 M is indicated at the concentration giving 50% response, (b) For an agonist alone, Aq, and in the presence of increasing amounts of irreversible receptor antagonists, B—F. There is a progressive rightward shift of the dose—response curve prior to reduction of maximum response. This pattern is consistent with the presence of a receptor reserve.

A critical component of the G-protein effector cascade is the hydrolysis of GTP by the activated a-subunit (GTPase). This provides not only a component of the amplification process of the G-protein cascade (63) but also serves to provide further measures of dmg efficacy. Additionally, the scheme of Figure 10 indicates that the coupling process also depends on the stoichiometry of receptors and G-proteins. A reduction in receptor number should diminish the efficacy of coupling and thus reduce dmg efficacy. This is seen in Figure 11, which indicates that the abiUty of the muscarinic dmg carbachol [51 -83-2] to inhibit cAMP formation and to stimulate inositol triphosphate, IP, formation yields different dose—response curves, and that after receptor removal by irreversible alkylation, carbachol becomes a partial agonist (68). 

Fig. 11. Dose—response curves for (A,A) inhibition of cyclic AMP formation and stimulation of IP formation by carbachol (A,D) before and (A,H) after reduction of receptor number by irreversible alkylation (carbachol) is in M. Error bars ( ) are shown for some studies.

R. J. Taharida and L. S. Jacob, The Dose—Response Curve in Pharmacology, Springer Vedag, New York, 1979. 

Fig. 5. Toxic chemical dose—response curves (a) no effect (b) linear effect (c) no effect at low dose and (d) beneficial at low dose.

Fig. 6. The stimulus perceived as color is made up of the spectral power (or, as here, energy) curve of a source times the spectral reflectance (or transmittance) curve of an object times the appropriate spectral response curves (one shown here) of the eye (3).

Slightly less sophisticated are spectrocolorimeters that determine spectral response curves for further computation but from which the spectral curve itself is not available. An example is the X-Rite 948. 

FIG. 8-75 Frequency response curves for a pneumatic positioner/actuator (a) input signal to stem travel for a 69-inch spring and diaphragm actuator with a 1.5-inch total travel and. 3-15 psig input pressure (h ) dynamic stiffness for the same positioner/actuator. 

A tracing of the electrode signal during a cycle of turning aeration off and on is shown in Fig. 24-15. The rate of supply is zero (after bubbles have escaped) in the first portion of the response curve thus, the slope equals the uptake rate by the organisms. When aeration is resumed, both the supply rate and uptake rate terms apply. The values for C — C can be calculated from the data, the slope of the response curve at a given point is measured to get dC/dt, and the equation can be solved for K a because all the other values are known. 

The biological response line for acute respiratory disease is a dose-response curve, which for a constant concentration becomes a duration-response curve. The shape of such a curve reflects the ability of the human body to cope with short-term, ambient concentration respiratory exposures and the overwhelming of the body s defenses by continued exposure. 

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