The analytical expressions for the van der Waals potential energy and force between two crossed carbon nanotubes are presented. The Lennard-Jones potential for two carbon atoms and the method of the smeared out approximation suggested by L.A. Girifalco were used. The exact formula is expressed in terms of rational and elliptical functions. The potential and force for carbon nanotubes were calculated. The uniform potential curves for single-and multi-wall nanotubes were plotted. The equilibrium distance, maximal attractive force, and potential energy have been estimated.

The erythrocyte sedimentation rate (ESR) test has been used for over a century. The Westergren method is routinely used in a variety of clinics. However, the mechanism of erythrocyte sedimentation remains unclear, and the 60 min required for the test seems excessive. We investigated the effects of cell aggregation during blood sedimentation and electrical conductivity at different hematocrits. A sample of blood was drop cast into a small chamber with two planar electrodes placed on the bottom. The measured blood conductivity increased slightly during the first minute and decreased thereafter. We explored various methods of enhancing or retarding the erythrocyte aggregation. Using experimental measurements and theoretical calculations, we show that the initial increase in blood conductivity was indeed caused by aggregation, while the subsequent decrease in conductivity resulted from the deposition of erythrocytes. We present a method for calculating blood conductivity based on effective medium theory. Erythrocytes are modeled as conducting spheroids surrounded by a thin insulating membrane. A digital camera was used to investigate the erythrocyte sedimentation behavior and the distribution of the cell volume fraction in a capillary tube. Experimental observations and theoretical estimations of the settling velocity are provided. We experimentally demonstrate that the disaggregated cells settle much slower than the aggregated cells. We show that our method of measuring the electrical conductivity credibly reflected the ESR. The method was very sensitive to the initial stage of aggregation and sedimentation, while the sedimentation curve for the Westergren ESR test has a very mild slope in the initial time. We tested our method for rapid estimation of the Westergren ESR. We show a correlation between our method of measuring changes in blood conductivity and standard Westergren ESR method. In the future, our method could be examined as a potential means of accelerating ESR tests in clinical practice.

We present an exact solution for the electrostatic field between a metallic hemi-ellipsoidal needle on a plate (as a cathode) and a flat anode. The basic idea is to replace the cathode by a linearly charged thread in a uniform electric field and to use a set of "image" charges to reproduce the anode. We calculate the field enhancement factor on the needle surface and ponderomotive force acting on the needle. Using the Fowler-Nordheim theory we obtain an exact analytical formula for the total current.

Contemporary biomedical research requires development of novel techniques for sorting and manipulation of cells within the framework of a microfluidic chip. The desired functions of a microfluidic chip are achieved by combining and integrating passive methods that utilize the channel geometry and structure, as well as active methods that include magnetic, electrical, acoustic and optical forces. Application of magnetic, electric and acoustics-based methods for sorting and manipulation have been and are under continuous scrutiny. Optics-based methods, in contrast, have not been explored to the same extent as other methods, since they attracted insufficient attention. This is due to the complicated, expensive and bulky setup required for carrying out such studies. However, advances in optical beam shaping and computer hardware, and software have opened up new opportunities for application of light to development of advanced sorting and manipulation techniques. This review outlines contemporary techniques for cell sorting and manipulation, and provides an in-depth view into the existing and prospective uses of light for cell sorting and manipulation.

In this study, a microfluidic-based physiometer capable of measuring the whole blood viscosity, hematocrit, and red blood cell (RBC) deformability on a chip is introduced.

Electrochemical impedance spectroscopy (EIS) is a highly promising tool for the analysis of blood.

No abstract

Relying on the obtained theoretical and expenmental results the electron work function from the nanotube carbon film was &mated. It was shown that these structures have a low work function, substantially lower than for graphite. Under estimation we regarded the influence of the film surface relief on its emission ability.Even first investigation results for electron field emission from the thin films containing nanotube carbon structures we developed [l] have shown that these films are promising for emission electronics [l-31. In the present paper we assess the work function of electrons from this material on the base of analyzing the experimentai results for field and thermal emission from the surface of thin nanotube carbon cluster (tubelene) films [4-51 and theoretical calculations.The studies of the nanotube film surface disclose [l-51 that they have an extremely appropriate geometry to construct field emitters when tubelenes are aligned orthogonally to the substrate surface. We have investigated two tubelene types [3-61. The former tubelenes are one-layer tubes of 8 A -1 1 A diameter which are twisted into 100 A -300 A diameter ropes. The letters represent multilayer tubes of 100 A -300 A diameter closed with the cap at the top. We call them, by convention, A and B tubelenes. The mean height of a single tubelene is 100 A .Since the tubelene conductivity is great (about 100 S. cm-1) and the tip radius is very small, a strong electric field arises at the top of the tubelene with applying the potential difference. between the anode and the film under study. This circumstance seems to be one of the factors defining the onset of electron field emission from these carbon films with comparatively low accelerating voltages. Numerical experiments were conducted to study the geometry of the tubelene film. The conductivity of electric field at the emitting surface of the tubelene was calculated using the method of finite elements [7]. So, we estimate, for example, the gain at the tubelene top for a height of a single tubelene of 100 A , its diaqeter of 30 A and an anode-cathode spacing of 20 mkm. With a zero potential at the cathode and the accelerating voltage at the anode U,=lOOO V the maximum field intensity at the top of the tubelene is 0.4 107 V/cm-3. Thus, with a specified geometry of the tubelene film a maximum gain makes up 10. This gain is insufficient to account for the experimentally obtained values of field emission current [4] (in experiment the current was 100 mkm with Ua=lOO V and the anode diameter was 0.6 mkm).Consequently the emission ability of the carbon tubelene film is due to one further factor, and namely, a low work function.In connection with this the Fowler-Nordheim formula was used to calculate the work function versus the number of tubelenes placed at the 0.6 mm diameter cathode. Computation was performed with regard to experimental field emission currents for a theoretically calculated gain at the tubelene tops. Figure 1 presents the work function cp versus Zn (N,JN) where N,, is the maxim...