Extinction phase

Figure 5.2 A model of the learning curve built into the CPE assay. During the acquisition phase, the level of the CR increased up to a maximum value at the third conditioning trial (A). This value is an indicator of the bee s ability to get conditioned properly, and can be compared according to the treatments. During the extinction phase, the level of the CR slowly decreased, back to the initial level of spontaneous response (B). This expresses the resistance of the bee s response to successive presentations of the unrewarded CS. Values in T1 and T5 are commonly used to compare responses of bees subjected to different treatments.

The extinction process, when the CS is delivered alone, can also be used to indicate potential effects of toxic compounds. The acquisition phase shows the ability of treated animals to learn the temporal relation between the US and the CS, whereas the extinction phase indicates their resistance to extinguish the response to a CS no longer associated with a reward. Ingestion of dicofol [34], endosulfan [35, 46], imidacloprid, and hydroxy-imidacloprid [48] significantly reduced the level of conditioned responses in both acquisition and extinction phases. By contrast, the response level was not reduced in bees conditioned prior to an exposure to permethrin... 

In ellipsometry monochromatic light such as from a He-Ne laser, is passed through a polarizer, rotated by passing through a compensator before it impinges on the interface to be studied [142]. The reflected beam will be elliptically polarized and is measured by a polarization analyzer. In null ellipsometry, the polarizer, compensator, and analyzer are rotated to produce maximum extinction. The phase shift between the parallel and perpendicular components A and the ratio of the amplitudes of these components, tan are related to the polarizer and analyzer angles p and a, respectively. The changes in A and when a film is present can be related in an implicit form to the complex index of refraction and thickness of the film. 

The ultraviolet absorption spectrum of thiazole was first determined in 1955 in ethanolic solution by Leandri et al. (172), then in 1957 by Sheinker et al. (173), and in 1967 by Coltbourne et al. (174). Albert in 1957 gave the spectrum in aqueous solution at pH 5 and in acidic solution (NHCl) (175). Nonhydroxylic solvents were employed (176, 177), and the vapor-phase spectrum was also determined (123). The results summarized in Table 1-15 are homogeneous except for the first data of Leandri (172). Both bands A and B have a red shift of about 3 nm when thiazole is dissolved in hydrocarbon solvents. This red shift of band A increases when the solvent is hydroxylic and, in the case of water, especially when the solution becomes acidic and the extinction coefficient increases simultaneously. 

The solvent used was 5 %v/v ethyl acetate in n-hexane at a flow rate of 0.5 ml/min. Each solute was dissolved in the mobile phase at a concentration appropriate to its extinction coefficient. Each determination was carried out in triplicate and, if any individual measurement differed by more than 3% from either or both replicates, then further replicate samples were injected. All peaks were symmetrical (i.e., the asymmetry ratio was less than 1.1). The efficiency of each solute peak was taken as four times the square of the ratio of the retention time in seconds to the peak width in seconds measured at 0.6065 of the peak height. The diffusivities obtained for 69 different solutes are included with other physical and chromatographic properties in table 1. The diffusivity values are included here as they can be useful in many theoretical studies and there is a dearth of such data available in the literature (particularly for the type of solutes and solvents commonly used in LC separations). 

H. Takayasu, N. Inui, A. Y. Tretyakov. Extinction, survival, and dynamic phase transition of branching annihilating random walk. Phys Rev Lett 65 3060-3063, 1992. 

Ozin et al. 107,108) performed matrix, optical experiments that resulted in the identification of the dimers of these first-row, transition metals. For Sc and Ti (4s 3d and 4s 3d, respectively), a facile dimerization process was observed in argon. It was found that, for Sc, the atomic absorptions were blue-shifted 500-1000 cm with respect to gas-phase data, whereas the extinction coefficients for both Sc and Scj were of the same order of magnitude, a feature also deduced for Ti and Ti2. The optical transitions and tentative assignments (based on EHMO calculations) are summarized in Table I. 

Malondialdehyde (MDA) was determined with thiobarbituric acid as described by Mihara et al. (ref. 15). The absorbance of butanol phase containing the aldehyde was measured at 532 nm. Calculations were made using the extinction coefficient according to Casini et al. (ref. 16). 

Although such experiments could be carried out, in practice it is usually much more accurate to measure complete extinction rather than ratios of non-zero intensities. This is accomplished by using a compensator (a wave plate) to restore linear polarisation to the reflected ray by the introduction of a known phase difference between the S- and P-components. The restored... 

By employing an extinction coefficient for the anion radical obtained from the pulse radiolysis experiments, the concentration of the radical could be calculated, and plotted against /c. The straight line plot so obtained was taken as strong evidence for the ECE mechanism, i.e. the solution phase attack of C02 on C02, thus fully resolving the controversy over the identity and state of the intermediate. From the slope of the plot the authors obtained the rate constant k2 as 7.5 x I03dm3mol 1 s 1. 

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