Heart rate depends on a feedback circuit through the autonomic nervous system. Microvascular disease (diabetes), denervation (heart transplant), and drugs can all alter the variabilility.
There actaully is a large literatuee in fetal heart rate variability used to diagnoses fetal distress and precipirate energent cesarian section. Sent via the Samsung Galaxy S™ III, an AT&T 4G LTE smartphone -------- Original message -------- From: Jim Lux <[email protected]> Date: 11/30/2013 6:41 PM (GMT-05:00) To: [email protected] Subject: Re: [time-nuts] simulation of interconnected clocks On 11/30/13 2:15 PM, Tom Van Baak wrote: > Jim, > > Could you just replay real data instead of trying to generate > simulated data? There's plenty of storage with Arduino or SD card > shields. > > Attached is frequency and ADEV of my heart beat for 10 hours. You > could do the same. In this case the flicker floor is just under 1e-1 > from 10s to 10ks. > > One could do that. Or in a limited sense, have a shorter table which you play back repetitively. If you did some processing on your heartbeat data to remove the sinusoidal modulation from respiration, you might find the ADEV/phase noise is less. That's something I'm looking into. In my case, I need to be able to generate multiple different realistic targets. I could probably record a bunch of sequences and then play back different pieces of them. or use one person and have them breathe at different rates and depths. But an algorithmic approach is interesting. And even more interesting is being able to generate a particular pattern (using the model), and see if you can retrieve the model parameters using the device. Here's where I'm using it: http://www.jpl.nasa.gov/news/news.php?release=2013-281 http://www.jpl.nasa.gov/news/news.php?release=2013-290 http://www.jpl.nasa.gov/video/?id=1252 We use the model parameters to distinguish targets from one another (and targets from bystanders and the operator); and also to separate humans from other targets (oddly enough, that slowly rotating fan, or swinging grandfather clock pendulum have much lower 1/f noise than your heart). One finds as you delve into the physiology literature that they have exceedingly different ways to measure, describe, and model things than engineers do. In some cases it's because they're working from the biological structures that make it happen. In others, it's just because historically it's been described differently: often with reference to particular methods of recording the signal. It's kind of like how the Richter scale is in terms of the height of the trace in mm on a particular kind of seismograph. Someone goes out and records ECG data and they write the paper and say "data was recorded using a Grass model X with the filter set at position 3", and since everyone in that field of research uses the same machines, they all know how it was recorded, and can duplicate it if needed. The signal processing details of the Grass Model X with filter set at Position 3 might be left as an exercise for the reader (or a letter to Al Grass at the Grass Instrument Company). The same thing happens in the nuclear instrumentation area, where everything is in terms of pulses and time domain processing, and you refer to a particular model of Ortec pre-amp, feeding some other model discriminator, finally feeding your multichannel analyzer (which name confused me, since it has only one input channel). The other thing is that a until recently, computers weren't used to analyze the data, so the analytical methods tend to favor those that are paper, pencil, and slide rule tractable. There's a lot of log/log plots with visually placed curve fits, with not a huge number of test subjects (20 subjects would be a lot in most of these papers). Finally, there might be a historical reason why decent math models aren't popular: The grand man of physiology was Carl Ludwig in Leipzig: he had hundreds of postgraduate students (Pavlov was one), but apparently "he had little use for mathematical treatment of biological problems". Ludwig wrote the 1847 paper everyone cites as the beginning: "Beitraege zur Kenntniss des Einflusses der Respirations bewegungen auf den Blutlauf im Aortensysteme". But hey, if your supervisor says math models aren't important, you're sure not going to argue with him, and someone of distinctly math modeling bent would likely find another place to study or field of study. So Ludwig casts a long shadow on published research, probably for 2 or 3 generations. Thanks to the miracle of the internet and big efforts to scan stuff this kind of thing is readily available. It's come a long ways since I had to hunt down a copy of Paschen's paper/thesis on high voltage breakdown as an actual printed copy and then photocopy it. http://archive.org/stream/beitrgezurkenn00hein#page/n55/mode/2up has some examples of data collected later in the 19th century from dogs and cats. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
