Search

In conventional two-dimensional infrared (2D-IR) spectroscopy, the inherently short vibrational lifetimes limit the time window to observe molecular dynamics typically to tens of picoseconds. The rather complex dynamics of organized molecular systems (e.g., glass formers, polymers, membranes, proteins), however, span a wide range of timescales from femto- to microseconds and beyond. Vibrationally Promoted Electronic Resonance (VIPER) 2D-IR negates the limitations of 2D-IR spectroscopy, for its signal decays with the electronic lifetime. Here, we present 2-Isopropylthioxanthone as the first VIPER 2D-IR probe to exploit intersystem crossing, thereby covering even the microsecond timescale. We achieved the required signal-to-noise ratio and resolution by introducing the Fourier-transform approach to the VIPER 2D-IR pulse sequence. Now, we are in a position to monitor dynamics via spectral diffusion several orders of magnitude beyond the vibrational lifetime of 2D-IR labels.

Currently, acoustic methods are widely used as a way to detect pipeline leaks. This is due to the fact that the acoustic signal has sufficiently capacious information about the state of the pipeline. The effectiveness of acoustic monitoring depends on the correct extraction of this information from the diagnostic signal. Currently, there is a search for new, more effective methods for analyzing acoustic signals. The article proposes to apply the theory of fractals to determine pipeline leaks. One of the most accurate methods for determining the fractal dimension of time series is R/S analysis using the Hurst exponent. An experimental stand has been developed and created, which includes a steel pipeline with water circulating in it. Water leakage from the pipeline was simulated by installing discs with holes of different diameters. The discs were placed in a special fitting on the surface of the pipeline. Acoustic signals recorded from the pipeline surface at different leakages and water pressure were analyzed. A relationship has been established between the size of the leak and the Hurst exponent of acoustic signals. The proposed method is compared with spectral analysis. Empirical experience has proven that R/S analysis can be used to determine pipeline leaks, as well as their classification by size.