Modelling of cavitational erosion in the area of surfaces of smooth contact

A qualitative and numerical analysis of the differential equation, describing pulsation of a symmetrical cavity in the area of the contact of smooth surfaces with different curvatures, forming a slot is presented in this article. This particular model is a slot between a plane and a sphere. Qualitative reasons of high erosion activity of such a toroidal bubble are defined. The boundary values were found when solutions of the equation are either non-harmonic periodic and non-vanishing, or vanishing (i.e., the bubble bursts). The results of this article can be applied to the controlling tasks of ultrasonic cavitation processes.     

On dimensionless parameters for generalization pressure head and flow rate characteristics of centrifugal disk pumps

Experimental study was performed for operation of a centrifugal disk pump at atmospheric air pressure. The dimensionless parameters were developed for generalization of experimental data on flow rate and head of the pump. The method for calculation of a pumping curve and throttling characteristic was offered through use of semiemperical generalization formulas. The method ensures a good accuracy in calculations, which is proved by comparison of calculation and experimental data for the pump tested.     

Thermal Stability of the Structure and Optical Properties of Nanostructured TIO2 Films

Russian Physics Journal - The structure and optical properties of titanium dioxide films have been studied during annealing from 100 to 400°C. The films were obtained by ion-plasma...     

Dynamic Effects in Nucleation of Receptor Clusters

Nucleation theory has been widely applied for the interpretation of critical phenomena in nonequilibrium systems. Ligand-induced receptor clustering is a critical step of cellular activation. Receptor clusters on the cell surface are treated from the nucleation theory point of view. The authors propose that the redistribution of energy over the degrees of freedom is crucial for forming each new bond in the growing cluster. The expression for a kinetic barrier for new bond formation in a cluster was obtained. The shape of critical receptor clusters seems to be very important for the clustering on the cell surface. The von Neumann entropy of the graph of bonds is used to determine the influence of the cluster shape on the kinetic barrier. Numerical studies were carried out to assess the dependence of the barrier on the size of the cluster. The asymptotic expression, reflecting the conditions necessary for the formation of receptor clusters, was obtained. Several dynamic effects were found. A slight increase of the ligand mass has been shown to significantly accelerate the nucleation of receptor clusters. The possible meaning of the obtained results for medical applications is discussed.     

Ion beam synthesis and investigation of nanocomposite multiferroics based on barium titanate with 3d metal nanoparticles

Samples of nanocomposite multiferroics have been synthesized by implantation of Co⁺, Fe⁺, and Ni⁺ ions with an energy of 40 keV into ferroelectric barium titanate plates to doses in the range (0.5–1.5) × 10¹⁷ ions/cm². It has been found that nanoparticles of metallic iron, cobalt, or nickel are formed in the barium titanate layer subjected to ion bombardment. With an increase in the implantation dose, the implanted samples sequentially exhibit superparamagnetic, soft magnetic, and, finally, strong ferromagnetic properties at room temperature. The average sizes of ion-synthesized 3d-metal nanoparticles vary in the range from 5 to 10 nm depending on the implantation dose. Investigation of the orientation dependence of the magnetic hysteresis loops has demonstrated that the samples show a uniaxial (“easy plane”) magnetic anisotropy typical of thin granular magnetic films. Ferromagnetic BaTiO₃: 3d metal samples are characterized by a significant shift of the ferromagnetic resonance signal in an external electric field, as well as by a large (in magnitude) magnetodielectric effect at room temperature. These results indicate that there is a strong magnetoelectric coupling between the ferroelectric barium titanate matrix and ion-synthesized nanoparticles of magnetic metals.     

Atomic-scale spin-polarized scanning tunneling microscopy applied to Mn3N2(010)

Atomic-scale spin-polarized scanning tunneling microscopy is demonstrated in the case of the unique surface spin structure of Mn3N2(010) at 300 K. We find that the surface spin structure is manifested as a modulation of the normal atomic row height profile. The atomic-scale spin-polarized image is thus shown to contain two components, one the normal, nonpolarized part, and the other the magnetic, spin-polarized part. A method is presented for separating these two spatially correlated components, and the results are compared with simulations based on integrated local spin density of states calculated from first principles.     

Nanostructure manipulation device for transmission electron microscopy: application to titania nanoparticle chain aggregates.

Experimental difficulties in studying nanostructures stem from their small size, which limits the use of traditional techniques for measuring their physical properties. We have developed a nanostructure manipulation device to apply tension to chain aggregates mounted in a transmission electron microscope. A 1-mm-long slit was cut in the center of a lead-tin alloy disc, measuring 3 mm in diameter and 200 microm in thickness. The disc was heated to about 140 degrees C before it was pressed between two quartz slides. The disc was then thinned by mechanical dimpling and ion milling until holes developed around the slit. The edges of the slit were 0.2 to 3 microm in thickness while the gap between them was up to a few microns. This disc was bonded to the two plates of a cartridge. The slit could be widened or narrowed at controlled speeds of 0.5 to 300 nm/s. The system was tested using titania (TiO2) nanoparticle chain aggregates (NCA) deposited across the slit. The ends of the NCA remained attached to the edges of the slit, which was widened at about 0.7 nm/s. In this way, the NCA was stretched up to 176% of its initial length before breaking.     

Electron Microscopy Study of Surface Islands in Epitaxial Ge3Sb2Te6 Layer Grown on a Silicon Substrate

Crystallography Reports - Islands in the form of truncated triangular pyramids on the surface of an epitaxial Ge3Sb2Te6 layer grown on a Si(111) substrate are identified by scanning electron...