Comments on speckle interferometry with regard to displacements of the camera during an exposure

Displacements of single-lens-reflex camera, which lead to errors in measuring displacements of an object by speckle interferometry, are studied to make sure that cameras with focal plane shutters displace to some extent, regardless of ways of mounting.     

The asymptotic relative generation distribution of the closest common ancestor of the multitype Galton–Watson tree conditioned on non-extinction

We extend Geiger’s size-biased tree method to the multitype case to give another proof of Zubkov’s result that the asymptotic relative generation distribution of the closest common ancestor of the multitype Galton–Watson branching process conditioned on non-extinction is uniform.     

Curvature-dependent excitation propagation in cultured cardiac tissue

The geometry of excitation wave front may play an important role on the propagation block and spiral wave formation. The wave front which is bent over the critical value due to interaction with the obstacles may partially cease to propagate and appearing wave breaks evolve into rotating waves or reentry. This scenario may explain how reentry spontaneously originates in a heart. We studied highly curved excitation wave fronts in the cardiac tissue culture and found that in the conditions of normal, non-inhibited excitability the curvature effects do not play essential role in the propagation. Neither narrow isthmuses nor sharp corners of the obstacles, being classical objects for production of extremely curved wave front, affect non-inhibited wave propagation. The curvature-related phenomena of the propagation block and wave detachment from the obstacle boundary were observed only after partial suppression of the sodium channels with Lidocaine. Computer simulations confirmed the experimental observations. The explanation of the observed phenomena refers to the fact that the heart tissue is made of finite size cells so that curvature radii smaller than the cardiomyocyte size loses sense, and in non-inhibited tissue the single cell is capable to transmit excitation to its neighbors.     

Effect of glass fiber-matrix polymer interaction on fatigue characteristics of short glass fiber-reinforced poly(butylene terephthalate) based on dynamic viscoelastic measurement during the fatigue process

Fatigue behaviors of glass fiber-reinforced poly(butylene terephthalate) (PBT) were studied based on dynamic viscoelastic measurements during the fatigue process. The fatigue strength of glass fiber-reinforced PBT was greatly improved by strengthening the interfacial adhesion between glass fiber and matrix PBT. The heat generation rate under cyclic fatigue for PBT reinforced with surface-unmodified short glass fiber was always larger than that reinforced with surface-modified short glass fiber because of the large net imposed strain amplitude of PBT matrix which occurred due to the interfacial debonding under cyclic fatigue. A fatigue fracture criterion based on the magnitude of hysteresis energy loss being consumed for a structural change was established for the PBT/short glass fiber composites in consideration of glass fiber-matrix polymer interfacial interaction. © 1994 John Wiley & Sons, Inc.     

Adsorption and electron properties of thin nickel films on W(110) surface

The evolution of the properties of ordered nickel films with thicknesses increasing from one to three atomic monolayers (ML) adsorbed on the W(110) single crystal surface is studied under ultrahigh vacuum conditions by the methods of reflection-absorption infrared spectroscopy (RAIRS) and ultraviolet photoelectron spectroscopy (UPS). The film structure corresponds to that of the Ni(111) single crystal face. The RAIRS technique is used to study the vibrational properties of the probing NO molecules adsorbed on the nickel films studied. In the course of the nickel film growth, whereby its thickness increases from 1 to 3 ML, both the vibrational and photoelectron spectra exhibit significant variation, which is indicative of a change in the adsorption and electron properties of the film. Stabilization of the IR and photoelectron spectra at a film thickness of 3 ML indicates that this thickness corresponds to the formation of the main adsorption and electron properties of the deposit. At the same time, the vibrational spectra of NO molecules adsorbed on a monoatomic nickel film exhibit features typical of adsorption on the W[110] surface of a massive tungsten crystal.     

Digital photocontrol of the network of live excitable cells

Recent development of tissue engineering techniques allows creating and maintaining almost indefinitely networks of excitable cells with desired architecture. We coupled the network of live excitable cardiac cells with a common computer by sensitizing them to light, projecting a light pattern on the layer of cells, and monitoring excitation with the aid of fluorescent probes (optical mapping). As a sensitizing substance we used azobenzene trimethylammonium bromide (AzoTAB). This substance undergoes cis-trans-photoisomerization and trans-isomer of AzoTAB inhibits excitation in the cardiac cells, while cis-isomer does not. AzoTAB-mediated sensitization allows, thus, reversible and dynamic control of the excitation waves through the entire cardiomyocyte network either uniformly, or in a preferred spatial pattern. Technically, it was achieved by coupling a common digital projector with a macroview microscope and using computer graphic software for creating the projected pattern of conducting pathways. This approach allows real time interactive photocontrol of the heart tissue.     

Superconducting Double Perovskite Bismuth Oxide Prepared by a Low‐Temperature Hydrothermal Reaction

Perovskite‐type structures (ABO₃) have received significant attention because of their crystallographic aspects and physical properties, but there has been no clear evidence of a superconductor with a double‐perovskite‐type structure, whose different elements occupy A and/or B sites in ordered ways. In this report, hydrothermal synthesis at 220 °C produced a new superconductor with an A‐site‐ordered double perovskite structure, (Na_0.25K_0.45)(Ba_1.00)₃(Bi_1.00)₄O₁₂, with a maximum T_c  of about 27 K.     

Spontaneous mode-selection in the self-propelled motion of a solid/liquid composite driven by interfacial instability

Spontaneous motion of a solid/liquid composite induced by a chemical Marangoni effect, where an oil droplet attached to a solid soap is placed on a water phase, was investigated. The composite exhibits various characteristic motions, such as revolution (orbital motion) and translational motion. The results showed that the mode of this spontaneous motion switches with a change in the size of the solid scrap. The essential features of this mode-switching were reproduced by ordinary differential equations by considering nonlinear friction with proper symmetry.