Method of evaluation of process of red blood cell sedimentation based on photometry of droplet samples
The paper focuses on research aimed at creating and testing a new approach to evaluate the processes of aggregation and sedimentation of red blood cells for purpose of its use in clinical laboratory diagnostics. The proposed method is based on photometric analysis of blood sample formed as a sessile drop. The results of clinical approbation of this method are given in the paper. Analysis of the processes occurring in the sample in the form of sessile drop during the process of blood cells sedimentation is described. The results of experimental studies to evaluate the effect of the droplet sample focusing properties on light radiation transmittance are presented. It is shown that this method significantly reduces the sample volume and provides sufficiently high sensitivity to the studied processes.
Reliable TLDA-microvolume UV spectroscopy with applications in chemistry and biosciences for microlitre analysis and rapid pipette calibration
A TLDA-microvolume (transmitted light drop analyser) accessory for use with a standard UV–visible fibre spectrophotometer is described. The physics of the elegantly simple optical design is described along with the experimental testing of this accessory. The modelling of the arrangement is fully explored to investigate the performance of the drop spectrophotometer. The design optimizes the focusing to deliver the highest quality spectra, rapid and simple sample handling and, importantly, no detectable carryover on the single quartz drophead. Results of spectral measurements in a laboratory providing NIST standards show the closest correlation between modelled pathlength and experimental measurement for different drop volumes in the range 0.7–3 µl. This instrument accessory delivers remarkably accurate and reproducible results that are good enough to allow the accessory to be used for rapid pipette calibration to avoid the laborious weighing methods currently employed. Measurements on DNA standards and proteins are given to illustrate the main application area of biochemistry for this accessory. The accessory has a measurement range of at least 0–60 A units without sample dilution and, since there exists an accurate volume–pathlength relationship, the drop volume used in any specific measurement or assay should be optimized to minimize the photometric error. Studies demonstrate that the cleaning of the drophead with lab wipes results in no measurable carryover. This important practical result is confirmed from direct reading of the accessory and an analytical balance which was used to perform carryover studies.
Small-angle multiple scattering of light in a random medium
Small-angle multiple scattering of unpolarized light in a random medium with large-scale irregularities is considered. The intensity and degree of polarization of the scattered radiation are calculated. Their sensitivity to the angular dependence of the cross section for an individual scattering event are studied. For the case of a scattering phase function that falls off according to the power law du ld i lm y-", where y is the individual scattering angle, it is shown that both the angular distribution of the radiation as a whole and the degree of polarization at relatively small scattering angles depend substantially on the index a. This dependence is analyzed both in the case of purely elastic scattering and for strongly absorbent media. O 1995 American Institute of Physics.