Measurements and Results

To set up the lifetime experiment, fluorescence excitation spectra were recorded using pulses of 90 ns duration corresponding to a spectral bandwidth of 15 MHz at a repetition rate of 1 MHz. The bandwidth was limited by the pulses rise and fall times, the pulse shapes and the frequency jitter of the laser. Fig. 8(a) shows a typical spectrum with four individual molecular resonances A, B, C and D. On average, the lines are about 25 MHz wide as compared to a homogeneous linewidth of about 8 MHz measured by earlier experiments using cw radiation and lower excitation energies. The best fit of the absorption profile of molecule C was obtained using a Lorentzian profile with a FWHM of 27 MHz. 

The spectrum in Fig. 8(b), shows the effect of a pulse width reduction to 9 ns. This spectrum represents the conditions under which the actual fluorescence lifetime measurements were performed. Due to the shorter pulse duration, the spectral width of the excitation light severely broadens the molecular resonances. In this case typical linewidths of 75 MHz were observed. Fitting again the profile of molecule C, the best results were obtained using a Gaussian lineshape with a FWHM of 73 MHz. The resonances of molecules A and B are separated by 60 MHz. In spectrum (a) both resonances are clearly resolved. At a pulse duration of 9 ns both peaks cannot be distinguished any more so that both molecules are not suitable for the individual fluorescence lifetime measurements (spectrum 8b). Molecules C and D are ideal candidates, since they are clearly resolved and do not overlap even at 9 ns pulse duration. 

Previous lifetime measurements on higher concentrated samples [6, 13, 14] resulted in time constants of 21.7-24.5 ns and agree very well with the presented results on individual molecules. Although only four different molecules were investigated, all time constants fall within the experimental accuracy interval and the statistical variation is very low. The average of the four time constants is 24 ns (single exponential fit) with a standard variation of 0.5 ns or 2%. As expected, the lifetime of the excited molecule is not very sensitive to its local nano-environment. 

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Developing a meaningful method for reporting an experiment s result requires the ability to predict the true central value and true spread of the population under investigation from a limited sampling of that population. In this section we will take a quantitative look at how individual measurements and results are distributed around a central value. 

Bell-shaped probability distribution curve for measurements and results showing the effect of random error. 

Gryning, S. E., and Lyck, E., "Comparison between Dispersion Calculation Methods Based on In-Situ Meteorological Measurements and Results from Elevated- Source Tracer Experiments in an Urban Area." National Agency of Environmental Protection, Air Pollution Laboratory, MST Luft - A40. Riso National Laboratory, Denmark, 1980. 

K Eckschlager Errors, Measurements and Results in Chemical Analysis, Van Nostrand Reinhold, London 1969... 

In the paper from V. Matveyev of the Ukrainian State University of Chemical Engineering, an examination of the role of conductive carbon additives in a composite porous electrode is conducted. A model for calculation of the local electrochemical characteristics of an electrode is presented. A comparison on the polarization of the electrode as a function of the redox state of the electroactive species is emphasized in the model. The electrochemical reaction of chloranil (tetrachlorobenzoquinone) was measured and results compare favorably to calculations derived from the model. 

The infrared spectra for oxidation of COad adsorbed at 50 mV is shown in Fig. 2-38. While the start of COad oxidation is seen as low as 400 mV, the oxidation does not complete until as high as 675 mV. It can be concluded, therefore, that there are small amount of COad that is easier to oxidize than another when CO is adsorbed at 50 mV. These results agree well to the electrochemical measurements and results of other authors. ... 

The loss must be measurable in dollar figures, easy to measure, and result in a substantial loss. 

Narcisi, R. S. Ion and neutral composition measurements in the lower ionosphere. In Methods of measurement and results of lower ionospheric structure. Rawer, K. (ed.), pp. 207-218. Berlin Akademie-Verlag 1974... 

Figure 3 Examples of RBS measurements and results for different types of samples.

Carbon dioxide may also be estimated volumetrieally by absorption in concentrated potassium hydroxide solution from a volume of air. The diminution m volume is noted by direct measuring, and results of considerable accuracy can be obtained in this manner within a very few minutes.6... 

Mathematical calculations are an important part of chemistry. You will need your calculation skills to help you investigate many of the topics in this textbook. You will also need calculation skills to communicate your measurements and results clearly when you do activities and investigations. Chemistry, however, is more than measurements and calculations. Chemistry also involves finding and interpreting patterns. This is the focus of the next section. 

Table 6-2 Examples of Application of the Rubber Elasticity Theory to Biopolymer Gels System Measurement and Results... 

As the boundary moved down the U-tube, the resistance of the solution increased the galvanometer deflection was kept constant by decreasing the variable resistances. The movement of the boundary was followed with a travelling microscope, and the time taken to reach successive graduations was recorded on a stop-watch. Immediately after the experiment the galvanometer was calibrated to get an accurate value of the current used. The measurements and results are tabulated below. 

Administration of clldlnlum for 1 yr at 5.0, 25, and 50 mg/kg In the diet of rats did not result In drug-related toxicity. Blood counts, clinical-chemistry measures, and results of gross and microscopic studies remained within normal limits (28). 

The choice of MPE tubes for the test section allowed easier measurements and results closer to industrial reality. Further studies should put the stress on the accurate influence of channel geometry and confinement on heat transfer with diabatic flow visualisation and a large variety of channels configurations. 

Highly specific sodium electrodes have been developed in which the selectivity for sodium may be 10 times greater than that for potassium (C3, M19). With urine, the pH and potassium concentration should preferably be controlled, but this is unnecessary for blood. The potassium glass electrode is less selective and responds to NH/ and Na. Its selectivity may vary with age (M19). It can be used with blood only if corrections are made for sodium concentration according to Eq. (2) (M19, N2, N3), but when this is done, the electrode shows a linear response to potassium concentration. The precision of serum sodium and potassium measurements with electrodes was found to be better than those obtained by flame photometry (M19, N3). To compare the accuracy of the two methods, the results by flame photometry must be converted to concentrations in serum water. For most specimens, it was found that concentrations could be calculated satisfactorily from activity measurements and results by the two methods agreed (N3), but differences were noted with some samples. So far the cause of this has not been resolved, but it is possible that in future ionic activity will be recognized as a better diagnostic feature than ionic concentration (N3). 

Murai Y, Kitagawa A, Song X-Q, Ohta J, Yamamoto F (2000) Inverse Energy Cascade Structure of Turbulence in a Bubbly Flow (PIV measurement and results). JSME Int J Series B-Fluids and Thermal Engineering 43 (2) 188-196 Naot D, Rodi W (1982) Calculation of secondary currents in cannel flow. Proc Am Soc Civ Engrs 108 (HY8) 948-968... 

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