Millisecond data analysis

TD-NMR is performed on NMR spectrometers that are equipped with lower magnetic field strength magnets with relatively low field homogeneity. Thns, relatively short FlDs on the order of a few milliseconds are obtained and FT of this signal yields broad lines from which no chemical detail can be obtained. However, the data is rich in information regarding the relative amonnts of different phases that are present in a sample, snch as water and oil, liqnid and solid, crystalline and amorphous. The data can be approached in two ways - analysis of the FID or analysis of relaxation times and their relative distributions. 

Instruments of this type may also be used quite effectively to evaluate kinetics of time-dependent changes in foods, be they enzymatic or reactive changes of other types. The computerized data-acquisition capabilities of these instruments allow precise measurement of absorbance or fluorescence changes, often over very brief time periods ( milliseconds). This is particularly useful for analysis of fluorescence decay rates, and in measurement of enzymatic activity in situ. A number of enzyme substrates is available commercially which, although non-fluorescent initially, release fluorescent reaction products after hydrolysis by appropriate enzymes. This kinetic approach is a relatively underused capability of computerized microspectrophotometers, but one which has considerable capability for comparing activities in individual cells or cellular components. Fluorescein diacetate, for example, is a non-fluorescent compound which releases intensely fluorescent fluorescein on hydrolysis. This product is readily quantified in individual cells which have high levels of esterase [50]. Changes in surface or internal color of foods may also be evaluated over time by these methods. 

MS Dwell Time Dwell time describes the time spent on a single step in a SRM or SIM analysis. Longer dwell time results in fewer data points but better signal-to-noise ratio, and should be optimized to produce acceptable data for each consideration. Common SRM dwell times in LC-MS would be 25-300 milliseconds (ms). 

Figure 4 A schematic representation of the experimentai approach for time-resoived XAS measurements. XAS provides local structural and electronic information about the nearest coordination environment surrounding the catalytic metal ion within the active site of a metalloprotein in solution. Spectral analysis of the various spectral regions yields complementary electronic and structural information, which allows the determination of the oxidation state of the X-ray absorbing metal atom and precise determination of distances between the absorbing metal atom and the protein atoms that surround it. Time-dependent XAS provides insight into the lifetimes and local atomic structures of metal-protein complexes during enzymatic reactions on millisecond to minute time scales, (a) The drawing describes a conventional stopped-flow machine that is used to rapidly mix the reaction components (e.g., enzyme and substrate) and derive kinetic traces as shown in (b). (b) The enzymatic reaction is studied by pre-steady-state kinetic analysis to dissect out the time frame of individual kinetic phases, (c) The stopped-flow apparatus is equipped with a freeze-quench device. Sample aliquots are collected after mixing and rapidly froze into X-ray sample holders by the freeze-quench device, (d) Frozen samples are subjected to X-ray data collection and analysis.

The PL kinetics at various wavelengths are non-exponential (Fig. 2). Decay behavior analysis reveals a weak long-decay component on a millisecond scale and an intense faster component on a submilisecond scale. Its relative contribution is increasing monotonously with increasing photon energy. The time-resolved PL spectra recovered fi om kinetics data have confirmed the existence of the fast decay component at the short-wave branch of the PL spectrum which cannot be ascribed to electronic transitions in a 3d-shell of Mn " ions. 

One of the reasons of the insufficient reliability of micellisation kinetics data determined from dynamic surface tensions, consists in the insufficient precision of the calculation methods for the adsorption kinetics from micellar solutions. It has been already noted that the assumption of a small deviation from equilibrium used at the derivation of Eq. (5.248) is not fulfilled by experiments. The assumptions of aggregation equilibrium or equal diffusion rates of micelles and monomers allow to obtain only rough estimates of the dynamic surface tension. An additional cause of these difficulties consists in the lack of reliable methods for surface tension measurements at small surface ages. The recent hydrodynamic analysis of the theoretical foundations of the oscillating jet and maximum bubble pressure methods has shown that using these techniques for measurements in the millisecond time scale requires to account for numerous hydrodynamic effects [105, 158, 159]. These effects are usually not taken into account by experimentalists, in particular in studies of micellar solutions. A detailed analysis of... 

A study in 12 healthy subjects found that verapamil 80 mg three times daily given with dofetilide 500 micrograms twice daily for 3 days caused a 42% increase in the peak plasma levels of dofetilide from 2.4 to 3.43 nanograms/mL. There was a 26% increase in the AUC0.4, which was associated with a transient simultaneous increase in QTc of 20 milliseconds for dofetilide alone and 26 milliseconds for the combination. However, the AUCo.s was not significantly different. The manufacturer notes that an analysis of clinical trial data for dofetilide revealed a higher occurrence of torsade de pointes when verapamil was used with dofetilide. ... 

The continuous line is for Ff/iax taken as the mean of 30 data points. The open circles are representative of the semi log analysis when Fg is taken as the fluorescence intensity measured after 3 milliseconds of illumination. 

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