Deconvolution count

In this method cotton hairs are cut in large number of hair fragments 0.2 mm long. They are then mounted in liquid paraffin on a microscopic slide, and then 

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Fig. 4.3 Primary screening and deconvolution stage mass spectra. (A) The region of the negative ion mass spectra containing the ions of interest is shown for two compounds, in two replicate primary screening experi-ments. Full-scale y-axis intensity values are normalized to 308 counts per second for compound 4 (m/z 436) and 162 counts per second for compound 5 (m/z 498).

Sample preparation was given elsewhere [2]. Femtosecond fluorescence upconversion and picosecond time-correlated single-photon-counting set-ups were employed for the measurement of the fluorescence transients. The system response (FWHM) of the femtosecond fluorescence up-conversion and time-correlated single-photon-counting setups are 280 fs and 16 ps, respectively [3] The measured transients were fitted to multiexponential functions convoluted with the system response function. After deconvolution the time resolution was 100 fs. In the upconversion experiments, excitation was at 350 nm, the transients were measured from 420 nm upto 680 nm. Experiments were performed under magic angle conditions (to remove the fluorescence intensity effects of rotational motions of the probed molecules), as well as under polarization conditions in order to obtain the time evolution of the fluorescence anisotropy. 

The time resolution of the electronics in a single photon counting system can be better than 50 ps. A problem arises because of the inherent dispersion in electron transit times in the photomultiplier used to detect fluorescence, which are typically 0.1—0.5 ns. Although this does not preclude measurements of sub-nanosecond lifetimes, the lifetimes must be deconvoluted from the decay profile by mathematical methods [50, 51]. The effects of the laser pulsewidth and the instrument resolution combine to give an overall system response, L(f). This can be determined experimentally by observing the profile of scattered light from the excitation source. If the true fluorescence profile is given by F(f) then the... 

Dyads (1 - 4) were synthesized by the method described previously. Fluorescence spectra were measured in degassed acetonitrile solutions at 2S °C with a Hitachi 8S0 spectrofluorometer. The excitation wavelength was the Soret maximum. Fluorescence lifetimes were measured at 25 °C using a Horiba NAES-500 ns-fluorometer interfaced to an NEC PC-9801 RX personal computer. The excitation light below 420 nm was cut off with a glass filter. The fluorescence was detected by a single-photon counting system and analyzed as the sum of two exponential components after deconvolution of the instrument response function. NMR spectra were recorded on a JEOL JNM GX-270 NMR spectrometer. 

Although deconvolution is a wdl defined mathematical procedure, its a lication to fluorescence decay curves is attended with numerous difficulties owing to the counting enors and instmmental distortions that accompany sin e photon countii data. It is now generally accepted that least squares iterative reconvdution is the most satisfactory method of analymg nano cond decay data In its amplest... 

The present limitatkins in time resolution for the time-correlated photon counting technique are due to the time jitter in the detection electronics and the transit time spread in the photomultqjlier tube ( 500 ps). Mth future improvements in these components and using cw mode-locked lasers as an excitation source, deconvolution of fluorescence lifetimes to a few tens of picoseconds oidd be achieved. Alter-... 

Fluorescence lifetimes were measured by time-correlated single photon counting using a mode-locked, synchronously pumped, cavity-dumped pyridine I dye laser (343 nm) or Rhodamine 6G dye laser (290 nm). Emissive photons were collected at 90° with respect to the excitation beam and passed through a monochromator to a Hamamatsu Model R2809U microchannel plate. Data analysis was made after deconvolution (18) of the instrument response function (FWHM 80 ps). 

A more detailed picture of the energy-transfer sequence was revealed by additional kinetic analysis. Mimuro et al. obtained rise and decay curves for the individual chromophores by deconvolution ofthe time-resolved fluorescence spectra based on the relative intensities obtained by photon counting. The time-resolved fluorescence spectra could be computer-fitted to the reported emission spectra of nine major chromophores four belonging to the rod PC and the remaining five to the APC-core complex. 

Counting Interferences + Peak overlap intrinsic irradiation Deconvolution selection of proper decay times RNAA as an alternative, change energy peak in XRF... 

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