An improved design of optical sensor for long-term measurement of arterial blood flow waveform

We present here the improved design and development of optical sensor for non-invasive measurements of arterial blood flow waveform. The sensor is based on a physical principle of reflective photoplethysmography (PPG). As the light source we used serially connected infrared diodes whereas NPN silicon phototransistors were used as light detectors. The electronic components were molded into square package and poured with silicone. Such preparation produced an elastic superficies that allowed excellent attachment of the sensor on the skins surface. Moreover, a serial connection of infrared diodes and phototransistors completely eliminated signal artifacts caused by minor muscle contractions. The sensor recording performances were examined at the photoplethysmographic sites on three different arteries; the commune carotid, femoral and radial and, on each site the sensor demonstrated remarkable capability to make a consistent, reproducible measurements. Because of the advantageous physical and electrical properties, the new sensor is suitable for various cardiovascular diagnostics procedures, especially when long-term measurements of arterial blood flow waveform are required, for monitoring of different parameters in cardiovascular units and for research

Cation Effect on the Electronic Excited States of Guanine Nanostructures Studied by Time-Resolved Fluorescence Spectroscopy

The effect of metal ions on the excited states of guanine nanostructures, short d­(TG4T)₄ quadruplexes and long G4-wires, are studied by fluorescence spectroscopy. The steady-state emission spectra show that both systems exhibit a strong cation effect. Fluorescence decays and fluorescence anisotropy decays, recorded from the femtosecond to the nanosecond time-scale, reveal the following picture. In the presence of K⁺, emission arises mainly from delocalized ππ* states (excitons), whose decay spans several decades of times. In contrast, the fluorescence in the presence of Na⁺ is dominated by emission from charge transfer excited states decaying essentially on the subnanosecond time-scale. Such a difference is not due to the initially populated (Franck–Condon) states. The interproton distances derived from two-dimensional NMR measurements on the ground state of d­(TG4T)₄ show that the geometrical arrangement of guanines, governing the electronic coupling, is the same for both cations, in line with the UV absorption spectra. The observed cation effect is correlated with the excited state relaxation: the increased mobility of Na⁺ ions within the quadruplex favors trapping of ππ* excitons by charge transfer excited states, whereas such a process is hindered for the larger K⁺ ions. This is rationalized by quantum calculations on two stacked guanine tetrads

Light induced charge and energy transport in nucleic acids and proteins: general discussion

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