Optical analysis of red blood cell sediment formation

The red blood cell (RBC) sediment formation was studied using an optical method. The intensity of light transmitted through the blood sample was measured as a function of time and distance from the bottom of the sample. Blood was obtained from healthy donors and measurements were performed at initial hematocrits ranging from 30 to 50%. Sedimentation curves and time dependence of the intensity averaged along the height of the RBC suspension were determined to give a cumulative description of the process. Detailed analysis of the transmitted light intensity revealed a moving interface between sedimenting RBC aggregates and the forming of a deposit of the cells. It was shown that although there is no discontinuity in the intensity an averaged interface can be found. A novel curve describing the sedimentation process called the deposit formation curve was found. Below this curve a formation of the RBC deposit occurs. Firstly, this curve represents the position of the interface between sedimenting RBC aggregates and a forming deposit, secondly this curve coincides with the last part of the sedimentation curve.

First-order statistics of human stabilogram

We investigated the statistical properties of the centre of pressure (COP) vector during quiet standing, as measured on a force platform. To derive a statistical model for the data, the COP vector, locally averaged COP, and deviations from the average COP were analysed. Whereas indefinite multimodal distributions for the components of the COP were observed, the density functions of deviation from the averaged COP had reproducible properties. The anterior-posterior and mediolateral components of the deviations had in common that they were correlated variables with a non-circular statistic. The main axes of the equiprobability density curves were rotated with respect to the natural anterior-posterior and mediolateral directions. By means of more detailed statistical analysis of the data, two distinct populations of subjects were identified. In some cases we have found Gaussian distributions of the components of deviation from the average COP. In most cases the statistics was non-Gaussian. The average contrast, a new dimensionless characteristic quantity, independent of platform calibration, was introduced as a useful indicator of non-Gaussian effects in the postural control system.

Light scattering in the eye lens near the spinodal

Scattered light intensities measurements of the nuclear part of adult bovine lenses are reported. In the investigated samples the existence of a binary liquid phase separation from a metastable state is demonstrated by the phenomenon of hysteresis. Fluctuations near spinodal are studied by means of a tentative theoretical approach. Accordingly the scattered light intensities were analyzed reduced by the intensity obtained for the stable state of the system. Fluctuations in the stable state are ascribed to protein aggregates and are analyzed by means of random density fluctuation theory. To evaluate the correlation length of the fluctuations near spinodal the Ornstein-Zernike theory is adopted. Temperature dependence of the correlation length xi of the fluctuations near spinodal can be described by equation for critical fluctuations [formula: see text]. For the investigated lenses the exponent nu varies from 0.65 to 0.74 and the parameter xi 0 varies from 1.6 nm to 3.6 nm. The spinodal temperature Ts for the investigated samples is evaluated.

[Effect of ventricular and sequential stimulation on the left- ventricular systolic function]

Left ventricular systolic function at rest was determined by echocardiography and Doppler in 20 patients after dual chamber pacemaker implantation due to second and third degree A-V block. Measurements were performed in each patient during VVI and DDD mode pacing at three different atrio-ventricular (A-V) intervals: 100, 150 and 200 ms. The essential hemodynamic superiority of DDD stimulation over VVI mode in the form of significant increase of forward stroke volume index (SVI) and cardiac index (CI) during dual chamber stimulation at identical rate stimulation was observed. Closer individual analysis of the values of CI during DDD stimulation at three different A-V intervals (100, 150 and 200 ms) gave the possibility of programming optimal A-V intervals (the highest value of CI) for each patient. The sequential atrio-ventricular stimulation as compared to right ventricular stimulation essentially improves the left ventricular systolic function at rest in patients without symptoms of heart failure. Maximum hemodynamic advantage during DDD stimulation depends on individual selection of A-V delay in each patient.