A study of transient processes makes it necessary to consider the sequence of RR-intervals from the point of nonlinear dynamical systems, central to which is occupied by the concept of stability of the system and its measures - Lyapunov exponents. Since the use of the latter in the HRV is associated with difficulties due to a large stochastic component, developed a method of local Lyapunov exponents - M-indices. The method allows to analyze the parts of a record AECG arbitrary length and degree of nonlinearity and a statistically significant and robust to the stochastic component of the results.
Using the method defined by the index:
M0 - the average value of the largest Lyapunov exponent for the local study site HRV. Sign M0 index shows that prevails in the study site of HRV, + - acceleration, - - braking. A value of - the degree of non-linearity plot of HRV compared with the function exp (t).
If the test plot is linear, then M0 = 0. It is clear that for fixed M0 HRV records will also be close to zero.
M1 - the index for assessing the temporal changes in HRV record: Does the movement in the phase space of the expansion or contraction phase flow. Sign of the index M1 shows what happens to the phase flow on the test site of HRV, + - extension, - - compression. A value - the rate of change of the phase flow on the test site HRV compared with the function exp (t). If the test section is stationary or changes are strictly periodic in nature, M1 = 0.
M - a composite index that characterizes the nonlinear and non-stationary transient at the test site recording of HRV. The sign + means the non-linear movement with a primary increase in heart rate, - means a non-linear movement with a primary decrease in heart rate. The value of the index M indicates the degree of non-linearity and non-stationary transient HRV.
EOS - Sub-Nanosecond Transient Absorption Spectrometer
Video on a new version of the EOS software.
EOS is a broadband pump-probe sub-nanosecond transient absorption spectrometer with an extended time window. Its patent pending design utilizes a photonic fiber for probe light generation.
To the researchers using femtosecond transient absorption for studying ultrafast kinetics of photoinduced processes it is often desirable to extend the time window of investigation beyond several nanoseconds. The most widely used method in this case is Nanosecond Flash Photolysis. This technique requires a dedicated Q-switched laser with accompanying wavelength conversion equipment, laser table, additional flash photolysis spectrometer, etc. Outside of the need to set up an additional laser spectrometer, the main disadvantage of this method is its relatively low time resolution a typical IRF in the nanosecond flash photolysis experiment is 7-10 ns. Therefore even when combined the above two methods often do not allow for reliable measurements of sub-10 ns lifetimes. The EOS with its less than 1 ns time resolution and the electronically controlled pump-probe delay presents a perfect solution and in combination with the HELIOS provides continuous temporal coverage from femto- to milliseconds and beyond.
