Properties of calcium phosphate coatings deposited by high-power ion beam ablation plasma

Biocompatible hydroxyapatite coatings (Ca₁₀(PO₄)₆(OH)₂) are used in stomatology and orthopedic surgery as an original structure for production of medical materials. These coatings have been deposited on Si, Ti and VT15-alloy substrates from ablation plasma formed under the impact of pulsed high-power ion beams on a calcium phosphate ceramic target. The nanohardness, Young’s modulus, elastic recovery, adhesion of coatings to substrates, friction constant, and surface roughness were measured.     

Ultrafast structural dynamics with table top femtosecond hard X-ray and electron diffraction setups

The following tutorial review is directed to graduate students willing to be part of the emerging field of ultrafast structural dynamics. It provides them with an introduction to the field and all the very basic assumptions and experimental tricks involved in femtosecond (fs) diffraction techniques. The concept of stroboscopic photography and its implication in ultrafast science are introduced. Special attention is paid to the generation of ultrashort electron and hard X-ray pulses in table top setups, and a direct comparison in terms of brightness and temporal resolution between current table top and facility-based methodologies is given for proper calibration. This review is focused on ultrafast X-ray and electron diffraction techniques. The progress in the development of fs-structural probes during the last twenty years has been tremendous. Current ultrafast structural probes provide us with the temporal and spatial resolutions required to observe atoms in motion. Different compression approaches have made it possible the generation of ultrashort and ultrabright electron pulses with an effective brightness close to that of fs-hard X-ray pulses produced by free electron lasers. We now have in hand a variety of ultrafast structural cameras ready to be applied for the study of an endless list of dynamical phenomena at the atomic level of inspection.     

Imaging methods and their application at the ANKA synchrotron light source

The imaging methods used at the ANKA Synchrotron Light Source (Institute for Synchrotron Radiation, Karlsruhe Institute of Technology) are briefly reviewed. Examples of recent applications of the phase-contrast imaging method using a grating interferometer and fast radiography with optic flow data analysis to study static and moving biological objects are presented.     

Effect of Plasma Modification of Surface and Sterilization on Optical Characteristics of Polyethylene Terephthalate Track Membranes

Technical Physics - Effect of plasma modification of surface and sterilization processes on optical characteristics of a polyethylene terephthalate (PET) track membrane (TM) is studied. The TMs are...     

Investigation of solutions to one family of mathematical models of living systems

We consider a family of integral equations used as models of some living systems. We prove that an integral equation is reducible to the equivalent Cauchy problem for a non-autonomous differential equation with point or distributed delay dependently on the choice of the survival function of system elements. We also study the issues of the existence, uniqueness, nonnegativity, and continuability of solutions. We describe all stationary solutions and obtain sufficient conditions for their asymptotic stability. We have found sufficient conditions for the existence of a limit of solutions on infinity and present an example of equations where the rate of generation of elements of living systems is described by a unimodal function (namely, the Hill function).     

A two-dimensional model for extensional motion of a pre-stressed incompressible elastic layer near cut-off frequencies

A two-dimensional model for extensional motion of a pre-stressedincompressible elastic layer near its cut-off frequencies isderived. Leading-order solutions for displacement and pressureare obtained in terms of the long wave amplitude by direct asymptoticintegration. A governing equation, together with correctionsfor displacement and pressure, is derived from the second-orderproblem. A novel feature of this (two-dimensional) hyperbolicgoverning equation is that, for certain pre-stressed states,time and one of the two (in-plane) spatial variables can changeroles. Although whenever this phenomenon occurs the equationstill remains hyperbolic, it is clearly not wave-like. The second-ordersolution is completed by deriving a refined governing equationfrom the third-order problem. Asymptotic consistency, in thesense that the dispersion relation associated with the two-dimensionalmodel concurs with the appropriate order expansion of the three-dimensionalrelation at each order, is verified. The model has particularapplication to stationary thickness vibration of, or transientresponse to high frequency shock loading in, thin walled bodies.     

A Technique for Obtaining Thermal Resistance of the Dielectric-Substrate Contact under High-Intensity Irradiation

Heating of dielectric materials is investigated under irradiation of specimens by periodically pulsed ion-beams. The solution to the equation of thermal conductivity yields constrained variations of the specimen's temperature around its average value, with the repetition rate being that of the radiation-pulse frequency. Initially, the average variation-period temperature is found to grow, while after saturation it approaches a quasi-stationary value controlled entirely by the thermal resistance of the specimen-substrate contact under the same irradiation conditions. A method for the time-averaged dielectric temperature under saturation is proposed. Using this method, an express-technique for calculating thermal resistance of the dielectric-substrate contact is offered. It is based on periodically pulsed heating of the dielectric specimen by a moderate-density ion beam and precision measurements of the its average temperature. The error of the express technique is evaluated and so is its applicability range. A hypothesis is put forward that proceeding form this new method for thermal resistance one may determine the energy lost in ion sputtering.