Amax model

Both models have the disadvantage that the effect increases with increasing concentrations without an upper limit which is a highly unphysiologic behavior. Therefore, such models should be used with caution or better should not be used for extrapolation outside the observed range. The gold standard of the empirical PD models is the sigmoid Amax model with or without the Hill coefficient ... 

The most common function used to relate drug concentration c with effect is the Amax model ... 

Formation of the excited amide anion of coelenteramide as the light emitter in the luminescence reaction of coelenterazine was experimentally supported by the experiment of Hori et al. (1973a), in which 2-methyl analogue of coelenterazine was used as the model compound. The summary of their work is as follows In the presence of oxygen, la and lb in DMF emitted bright blue luminescence (Amax 480 and 470 nm, respectively), and produced the reaction products Ha and lib, respectively. The fluorescence emission of lib (Amax 470 nm) and that of the spent chemiluminescence reaction of lb, both in DMF plus a base (potassium r-butoxide), were identical to the chemiluminescence emission of lb in DMF. The fluorescence emission of Ha... 

Deviations between the actual ablation rates and those predicted using Eq. (2) occur at higher fluences. 64 65 Hence, a different rate equation is required to determine the relationship between amax and fluence. According to a rate model proposed by Sauerbrey and Pettit,46 the etch depth per pulse is given by... 

Ethylene Vffigjtal65 nm Ciuax l 5 X104 Benzene (perimeter model) Afiu> g2S6 nm emu 1.6x 10 Formaldehyde Amax=304 nm max 18... 

Structure (XII) with the attachment of the lactone bridge reversed can be ruled out for the following reason. Gibberellic acid decomposes slowly in aqueous solution to give gibberellenic acid first described by Gerzon, Bird, and Woolf (16) who suggested the homoannular diene structure (XV). We consider that the ultraviolet absorption (Amax 253 m/ e 22,400) is more in accord with the hetero-annular structure (XIV) and this is confirmed (25) by ultraviolet absorption (Amax 309 mfi e 16,500) of the derived dienone (XVII) which is decisive [cf. the ultraviolet absorption (Araax 310 m/ e 3900) of model cyclohexadienone (XVIII)]. 

Amax is shifted to 410 nm in 44 (c and g annelation) it is shifted to 422 nm. The explanation of this effect is quite straight forward. Benzo-annelation across a double bond substitutes a bond with half double bond character for a double bond. In terms of the exciton model this decreases both the length of the interacting system and the strength of the interaction. 

An accurate formula for the upper limit of these Amax in Da cannot be given. Hence it is recommended that individual vin values are found for every kinetic model. The stability of the matrix... 

At 638 nm in cyclohexane, the wavelength of maximum absorbance of the bis(naphtho[l,8-A ]thiopyranone) 628 is 98 nm to the red of thioindigo (Amax 540 nm). These values are in close agreement with those predicted by a TD-PBE0/6-311+G(2, />)//PBE0/6-311G6f,/>) approach that allowed for bulk solvent effects by means of a polarizable continuum model <2006JA2072>. 

The molar extinction coefficient (c) and Amax for the polymer and the model compound are almost identical, and the spectra are sufficiently similar to suggest that the nature of the absorption process is the same in both cases. 

It is interesting to note that these conclusions seem to be inapplicable to model protonated Schiff bases in solution. Thus Brith-Linder et al, (246) have shown that the C=C stretching frequency in a series of PRSB in a variety of solvents is almost independent of the spectral shift (vc=c = 1588 + 6 cm" in the range 435 nm < Amax < 542 ran). This implies that the excited state, rather than the ground state, is sensitive to the electrostatic effects of the counterion and to the solvent polarizability. This behavior which is in variance with the substantial slope of vs. Amax for the pigments as shown in Fig. 7, raises... 

The reactions of the OH radicals with two model thioether compounds, S-ethylthioacetate (SETAc) (H3C-CH2-S-C(=0)-CH3) and S-ethylthioacetone (SETA) (H3C-CH2-S-CH2-C(=0)-CH3, containing electron withdrawing acetyl groups in the a and f3 positions, with respect to the sulfur atom have been studied by pulse radiolysis. The a-positioned acetyl group in SETAc destabilizes >S -OH radicals within the five-membered structure that leads to the formation of alkyl-substituted radicals H2C -CH2-S-C(=0)-CH3 and H3C-CH2-S-C(-0)- CH2. At high proton and SETAc concentration, the OH-induced oxidation does not lead to intermolecularly three-electron-bonded dimeric radical cations SETAc(S.. S), only the a-(alkylthio)alkyl radicals H3C- CH-S-C(=0)-CH3 were observed (Amax = 420 nm). These observations are rationalized in terms of the... 

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