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Loss constant

Shell Chemical Company), exhibits a maximum at 300 nm, corresponding to that of the model chromophore anisole. The fluorescence intensity decreases monotonically with increasing concentration of 2,4-dihydroxybenzophenone (DHB) and, furthermore, decreases with time on continued excitation (274 nm) in the spectrophotometer. The fluorescence loss with time may be resolved into two exponential decays. Initially, a relatively rapid fluorescence loss is observed within 20 sec, followed by a slower loss. Loss constants for the initial (k ) and secondary (kj) exponential decays for 1.5 ym films (on glass slides) containing varying concentrations of DHB are provided in Table I (entries 1-3). The initial loss constants are seen to decrease more markedly with increasing DHB concentration than the secondary constants. [Pg.110]

In order to determine the effect of air on fluorescence loss, free films of polymer 1 (15 ym thick) were placed in a quartz cuvette, which was evacuated prior to excitation in the fluorescence spectrophotometer. Although the initial loss constant was not determined accurately, both constants (entry 4) were substantially smaller in vacuo relative to air. Fluorescence loss from correspondingly thick films in air is provided in entry 5. [Pg.110]

On continued excitation in the phase fluorimeter, the fluorescence lifetime of polymer 1 films also decreased with time. The lifetime decrease was exponential with an average loss constant of 8.2 1.2 x 10 lf sec-1 (1.5 pm thick film) from measurements at different sites on the film. These findings constitute direct evidence for RET from the polymer to a photoproduct(s) in support of the fluorescence intensity measurements. [Pg.111]

Method involves placing a specimen between parallel plate capacitors and applying a sinusoidal voltage (frequencies ranging from 1 mHz to 1 MHz) to one of the plates to establish an electric field in the specimen. In response to this field, a specimen becomes electrically polarized and can conduct a small charge from one plate to the other. Through measurement of the resultant current, the dielectric constant and dielectric loss constant for a specimen can be measured. The sharp increases in both the dielectric constant and the dielectric loss constant during a temperature scan are correlated with the occurrence of Tg... [Pg.75]

In the non-classifying continuous granulation experiments, a permanent discharge of particles is necessary to keep the bed mass and pressure loss constant this in turn is dependent on the amount of solid injected, the attrition, and the... [Pg.502]

Figure 20. Dielectric loss constant of plasma-polymerized (O) PPE, (A) PPEA,... Figure 20. Dielectric loss constant of plasma-polymerized (O) PPE, (A) PPEA,...
L stainless steel Decreased weight loss Constant potential (500mV vs. SCE) 10% serum (Brown et al, 1988)... [Pg.438]

The above Eq. 6.4 has two heat loss constants that can be converted into single heat loss constant by using the thermal mass relationship between the copper and composite. For a body of uniform composition, thermal mass, C , can be approximated by Cfh = m Cp, where m is the mass of the body and Cp is the isobaric specific heat capacity of the material averaged over temperature range in question. Thus, the equivalent thermal mass for a copper plate to aerogel composite for a constant cross-sectional area (Axz) will be as follows ... [Pg.86]

The dielectric loss constant, e", or its associated tan 5 can be measured by placing the sample between parallel plate capacitors and alternating the electric field. Polar groups on the polymer chain respond to the alternating field. When the average frequency of molecular motion equals the electric field frequency, absorption maxima will occur. [Pg.372]

Figure 9.23 Normalized dielectric constant o - s ( ), where Sq is the zero-frequency dielectric constant, and dielectric loss constant ( ) at 40 °C for a 6-arm polyisoprene star with = 459,000. Symbols are data ofWatanabeef a/. [66], and the lines are predictions of the slip link model. The parameters of the model = 4650 and Tq=42 s,are used for all calculations with the... Figure 9.23 Normalized dielectric constant o - s ( ), where Sq is the zero-frequency dielectric constant, and dielectric loss constant ( ) at 40 °C for a 6-arm polyisoprene star with = 459,000. Symbols are data ofWatanabeef a/. [66], and the lines are predictions of the slip link model. The parameters of the model = 4650 and Tq=42 s,are used for all calculations with the...
U18P3 (Calculated transient response fiM various reactivity stqis and heat loss constants (R) m U-235 systems 5k(t) = 6ko - B, Jo E(f le" dt ... [Pg.144]


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