Processing of physiological signals often involves detection of peaks and finding intervals between them. Well developed methods are available for Electrocardiogram(ECG) QRS complex detection. However, there are only a few algorithms published for peak detection suitable for pulse wave signals such as arterial pressure wave and photoplethysmographic (PPG) signals. Algorithms for detection of QRS complex in ECG are based on the impulsive character of the signal and are not applicable for pulse wave signals, which are more sinusoidal in nature and the shape varies with age. In this background, a versatile algorithm based on the physiology of the pulse wave is developed to detect the peaks from a pulse wave signal such as PPG. The algorithm combines the technique of moving average of valley-peak differences with an adaptive threshold filtering to detect the systolic peaks. The algorithm is validated against a publicly available validation dataset and achieved a sensitivity of 99.82 and a positive predictivity of 98.88 when compared to expert manual annotations. This algorithm is computationally simple and can be easily implemented in real time processing hardware.

The overwhelming interest in supercapacitors has led to the search for various carbonaceous materials, leading to hierarchical porous carbons. Herein, we report a natural biomass (tamarind seed)-based hierarchical porous carbon without any template and activated by a facile scheme. The tamarind seed coat-based hierarchical porous carbon possessed a unique configuration, making the material exhibit superior supercapacitor properties. A single carbon fiber hosting a distinctive micro- and mesoporous structure formed a connecting thread between the pores. This unique structure enabled high surface area and high capacitance. The highest surface area obtained by this method was 1702 m2 g–1, whereas the capacitance was 157 F g–1 in 6 M KOH. Further, an ionic liquid-based electrolyte revealed 78 F g–1 at a current density of 0.5 A g–1. Outstanding capacity retentions of 96 and 93% were obtained over 1000 cycles at a current density of 2 A g–1 for aqueous (6 M KOH) and ionic liquid (1-butyl 3-methyl imidazoliumbistrifluorosulfonylimide) electrolytes, respectively. The high charge-storage ability of the porous carbon microfibers (PCMFs) can be ascribed to the coexistence of micro- and mesopores. The power characteristics and the cyclic stability of PCMF materials were appealing in both electrolytes. The synthesis process described is amenable for large-scale applications with less complexity.

[1] The unusual fast fading observed around middays on line-of-sight microwave links in a tropical coastal area is described. Fading was as deep as 20-30 dB with fade rates double the normal rates. The fading is attributed to multipath propagation produced under sea breeze circulations. Sea breeze circulations modify the boundary layer and cause the formation of a low level super-refractive layer associated with a temperature inversion above the ground. At the same time, an elevated layer of high refractivity variance is formed at the boundary of the cool and humid marine air flowing on-shore and the relatively dry and hot air flowing offshore. However, when there is a strong vertical heat transfer from the ground, a modified convective boundary layer with a height of about 100-150 m above the ground with a capping elevated layer at the upper boundary of the sea breeze front is formed. In both cases, specular reflections and scattering of radio signals from the layered structures, along with multiple refractive paths are expected to be the cause of the observed fast daytime fading, which is conspicuously absent on inland paths.

Heart rate variability (HRV) analysis is gaining acceptance as a potential non-invasive means of cardiac assessment in clinical as well as research domains. Although it is a standard practice to derive HRV from the R-R peaks of electrocardiogram (ECG), there have been attempts to deduce it from peripheral pulse wave signal. HRV is measured using photoplethysmographic (PPG) pulse wave signal in this work. A versatile algorithm governed by the physiology of the cardiovascular system developed by the authors is used to derive peak intervals from the PPG signal. In addition to normal time and frequency domain techniques, sequential trend analysis (STA) is applied to analyse HRV. Out of 20 subjects monitored, the results of three, one healthy and two with known cardiac problems, are presented and discussed. In all cases monitored, the results of HRV deduced from PPG are in tune with clinical picture of the subjects. The usefulness of STA in the analysis of HRV is also discussed.

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