KEYWORDS: Fluid dynamics, Near infrared, Calibration, Water, Pulsed laser operation, Prototyping, Sensors, Temperature metrology, Data modeling, Refractive index
Fluidic measurement is a critical part of clinical care and homeostasis maintenance. This paper reports feasibility study
of measuring flow velocities over a wide dynamic range using a non-contact measurement technique, optical time-of-flight
(OTOF), with the objective of developing a compact instrument that can be used to measure fluid flow for IV
medication delivery. In this study, a 1480nm laser diode focused to a 20μm spot introduces a heat bolus into the fluid.
This localized temperature increase results in a correlated change in refractive index, detected downstream by observing
defocusing of the visible beam, focused to a 10μm spot in the center of the fluid path. The OTOF measurement provides
the centerline velocity of the fluid flow. CFD modeling ensured that laminar flow was fully developed; prior to the
OTOF measurement point, thus providing a simple, empirical relationship between OTOF and fluid velocity, and hence
volumetric flow rate. Measurements have been performed over a wide range of flow velocity from 1 mm/s to 1 m/s with
approximately ±5% measurement error for broad ranges of fluid properties such as viscosity (0.77-13.88 cp), density
(0.98-1.17 g/cm3) and temperature (5-35 °C). The dynamic range of measured velocity/flow rates is a function of the
distance between the heating and the detection laser beams.
Animas Corporation is developing a long-term (>5 years), implantable optical, blood glucose sensor based on near-infrared absorption spectroscopy. While the glucose sensing R & D community tends to over promise results to the general public without convincing scientific evidence due to the business potential for the sensing market, Animas would like to present solid data showing robust glucose calibration and prediction. In vitro data from whole blood in more than 500 patients, with various medical histories, shows an excellent correlation (R2=0.94) between glucose concentrations determined using sensor prediction and traditional fingerstick measurement. The numbers of outliers identified in the thousands of measurements from the 500 patient population are less than 1%. Better than 13 mg/dl accuracy was achieved in dogs in in-vivo testing. Glucose data showing excellent tracking between measurements with the Animas sensor and a Hemocue glucometer will be presented. One of the technical challenges of developing the Animas implantable sensor is to fabricate laser diodes that have stable emission spectra, especially for those that emit in wavelength above 2 μm. Requirements for various kinds of diode light sources will be discussed.
Fluorescence images were acquired form gynecological tissues for multiple combinations of emission and excitation wavelengths in the UV and blue spectral regions. The wavelength combinations were selected to highlight different tissue molecules whose fluorescence signatures have been shown to potential in the detection of malignancy. These images were analyzed to determine the size, shape and location of different tissue structures.
The critical role of two-photon (pi) -electron excited states in third order optical processes in squaraine dyes is described. The discussion is based on recently completed femtosecond measurements of the excited state absorption spectrum of a typical centrosymmetric squaraine. The new experimental data agree well with the earlier theoretical description and quantum many-electron calculations reported for the dye chromophores.
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