Optical Properties of Human Blood Sediment

The formation of human blood sediment by means of optical method was studied. Light was transmitted through a layer of blood. The temporal changes of the transmitted light intensity along the sample were measured. Samples of blood from a healthy donor were investigated. The optical method permits us to distinguish three phases of the blood sediment. At the top of the container the well-known supernatant plasma layer creates. In the sediment of the red blood two phases were distinguished. The rouleau formation phase and the phase of demixed blood were found. The two phases are separated by the moving boundary. The kinetics of this boundary was determined. The optical data admit to a hypothesis about the physical phenomena of the sedimentation process. The spinodal decomposition may be one of the mechanisms of the blood sediment formation

Fluctuations in settling velocity of red blood cell aggregates

Sedimentation of red blood cell aggregates was experimentally investigated by optical imaging. Suspensions of red blood cell at low hematocrit were obtained from blood of healthy donors. The velocity of three-dimensional red blood cell aggregates was measured using particle image velocimetry. The magnitude and spatial correlation functions of the velocity fluctuations of the settling aggregates were determined. It is shown that the fluctuations in the settling velocity exhibit characteristic correlations in the form of swirls. The formation of 3-D red blood cell aggregates leads to a large initial swirl. The growth of the aggregates and their sedimentation diminishes the swirls size

Lifetime and Collisional Depopulation Cross Section for the 142\text{}^{2}D3/2\text{}_{3}\text{}_{/}\text{}_{2} State of Rb

The lifetime τ and the cross section σ for depopulation induced by collisions with ground-state Rb atoms were measured for the 14$\text{}^{2}$D$\text{}_{3}\text{}_{/}\text{}_{2}$ state of Rb. The experiment was performed in the gas-cell conditions in a range of Rb vapour temperatures in the vicinity of 340 K. The lifetime value τ = 1970(130) ns, agrees with the theoretical prediction with allowance for the influence of blackbody radiation as well as of the effects due to core polarizability and spin-orbit interaction. The measured cross section σ = 6.5(3.1) × 10$\text{}^{-12}$ cm$\text{}^{2}$ is close to the geometrical cross section. This agrees with similar observations made by other authors for the case of the lower n$\text{}^{2}$D states of Rb

The Activity of the Postural Control System and Its Compensation in the Morbid Obese Subjects

The method based on two-dimensional stochastic process was used to examine the short-term postural sway under eyes-open and eyes-closed conditions. Obtained parameters, i.e., matrix of the fluctuation strength and friction coefficient, describe the stochastic activity of the muscles of the lower limbs as well as mechanisms compensating that activity. The standard force platform was used to measure the center of pressure displacements. In this investigation 17 control subjects and 22 morbid obese subjects were included. It is shown that the method is useful in the study of the postural control system of morbid obese subjects. The muscles responsible for postural control in these subjects have exhibited larger stochastic activity, than these muscles in non-obese subjects. However morbid obese as well as non-obese subjects compensate additionally enlarged level of muscles activity after closure of their eyes. The morbid obesity causes an increase of the muscles' force but does not cause the impairment of the postural control system

The fractal dimension of red blood cell aggregates in dextran 70 solutions

Fractal dimension of three dimensional red blood cell aggregates were determined by measurement of their size and sedimentation velocity. The sedimentation of the aggregates was investigated with red blood cells suspended in dextran 70 solutions at concentrations from 2 to 5 g/dL, at hematocrit 5% and 10%. The aggregate velocity and size were measured using an image analysis technique. The velocity vs. radius dependence of the aggregates exhibited a scaling behavior. This behavior showed the fractal structure of the aggregates. It is shown that the fractal dimension of the three dimensional red blood cell aggregates depends on the dextran concentration in the suspension. This parameter exhibited a minimum at dextran concentration between 3 and 4 g/dL. Thus the fractal dimensions increased as the aggregation extent decreased. The obtained results show that the sedimentation experiment together with image analysis is a promising technique to determine the fractal dimension of the three dimensional red blood cell aggregates