We have constructed a new LighTouchTM device having improved measurement and control of applied force and tissue
position in noninvasive probing of human volar side fingertip capillary beds in vivo using near infrared Raman
spectroscopy. These improvements have translated into improved capacity to observe and classify the behavior of
specific spectral features under tissue and pulse modulation. Using this and other measurements on various other
samples in vitro have demonstrated the validity of associating specific functions of the observed spectra with medically
relevant quantities like hematocrit and bicarbonate ion. In addition we can say more about how much of the observed
tissue modulated spectra must be associated with a "modulation defect" resulting from various errors affecting the
accuracy and precision in subtraction of static tissue contributions.
We have refined of our previously published tissue modulation technique for obtaining Raman spectra of blood in fingertip capillary beds. Results from the newest LighTouch device benefit from more consistent management of applied force and temperature and more consistent tissue placement. Comparing these more precisely obtained spectra with other spectra obtained from the same capillary beds using the natural heart driven pulse as modulation reveals essential aspects of microcirculation such as plasma skimming, the Faraeus effect and the Faraeus-Lindqvist effect. We discuss these results in the context of performing noninvasive quantitative analysis of blood and blood components in vivo. We show the first Raman spectra of human blood plasma noninvasive, in vivo.
We present a preliminary study of all-optical switching devices based on the photo and electrochromic behavior of sputtered and sol-gel based tungsten oxide films. While many questions remain unanswered these films show considerable promise for meeting a variety of switching applications. These switching applications complement the optical memory applications we have previously demonstrated. In the present study we have used 488 nm control light to switch 632 nm data light. The films range from about 100 nm to 900 nm in thickness and can be deposited on various substrates. The switching was characterized using single layer films. The switching time is currently submillisecond with incident control powers of just a few tens of milliwatts of control light using a spot size of about ten microns in diameter.
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