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Today, visual classification of the degree of lipemia in blood samples is frequently performed in clinical laboratories. However, achieving standardization of this classification at low cost and with fewer resources is an objective that is still under development. In this work, a comparison is made between the visual inspection and optical measurements of blood plasma for quantifying lipemia. The plasma refractive index’s real part was measured using an Abbe refractometer and transmittance measurements were made at a 589 nm wavelength and wavelengths ranging from 320 to 1100 nm in the spectral region, respectively. Taking the slope of the transmittance spectrum at two specific wavelengths, it is possible to establish a more standardized selection criterion and implement it quickly using low-cost optical devices. Furthermore, using the proposed transmittance-spectrum-slope method, statistically significant differences (p < 0.05) were found between healthy blood samples and lipemia 1, 2, 3, and 4. However, there were no statistical differences between lipemia 1 and 2.

We analyze the sensitivity of electrical measurements to lysis of biological cells in suspensions. We aim at discerning the electrical parameter and measuring conditions that are more convenient to monitor the kinetics of a lysis process. We consider single-frequency measurements of the capacitance and resistance of an electrical capacitor containing a suspension of biological cells at mid-radiofrequencies. We use well-established models to estimate the relative sensitivities to variations of the volume fraction of cells during a lysis process. Then we estimate values for the resolution in measuring the fraction of cells that have been lysed with commercially available LCR meters. Unexpectedly, our results indicate that, despite the total number of ions in solution remains constant during a lysis process, in general, the electrical resistance provides a more appropriate signal for sensing the evolution of cell lysis than the capacitance. This is contrary to the case when the cell's volume fraction without lysis is to be measured. We predict that, with single-frequency resistance measurements, a resolution better than 0.1% in volume fraction of lysed cells should be attainable without much difficulty. Keywords: Electrical sensing, Biological-cell suspensions, Lysis, Resistance, Capacitance, Effective dielectric function

We analyze theoretically and experimentally a new way of sensing the real and imaginary parts of the effective refractive index of nanocolloids by coherent reflectance from a confined film of a liquid sample. [...]

A parallel plate capacitor can be used as a high resolution sensor of the electrical characteristics [...]

We consider the non-linear interaction of non-collinear acoustical waves in gas media. Conditions for the resonant backscattering are formulated in analogy with the four-wave mixing known in optics. The efficiency of the phase-matched interaction is calculated in the resonant approximation for gas media. The possibility of using the resonant backscattering as a remote acoustical probe in the atmosphere is analyzed. It is found that for acoustical waves with wave number 10 m-1, sources of size 1 m, and a distance to the interaction region of 100 m the amplitude of the reflected wave can be larger than 10-10 times the atmospheric pressure.

This paper addresses a long-standing concern of whether one can measure the refractive index of a turbid colloid as if it were an equivalent homogeneous medium using standard techniques. We analyze the accuracy of determining the effective refractive index of turbid colloids when measuring the critical angle by reflection of light in an internal reflection configuration and then using Snell’s law. It is assumed that the critical angle is taken as the inflection point of the reflectance curve and that the effective refractive index of the turbid colloid is well approximated by the van de Hulst approximation. Experimental measurements are used to show the viability of measuring the inflection point of an angular-reflectance curve with highly turbid colloids. The refractive index of aqueous suspensions of and latex particles (sizes in the range of 100–500 nm) were determined with an accuracy of  ±0.0025. Then, a multiple-scattering model for the coherent reflection of light from turbid colloids is used to produce 2D maps of the estimated error in determining the effective refractive index of turbid colloids by the critical angle method as a function of the size and volume-filling fraction of the colloidal particles. [ABSTRACT FROM AUTHOR]