Asymptotic analysis and design of diffractive optical elements

The problem of light diffraction by a micro-optical diffractive element is investigated. The method of stationary phase is applied to obtain approximate values of the integrals in the Kirchhoff approximation. The accuracy of the asymptotic approximation is studied in detail. As an application, the obtained approximate formulas are used to solve a design problem of constructing a diffractive optical element with a desired intensity distribution.     

Real-time and postprocessing holographic effects in dichromated pullulan

Experimental results concerning both real-time and postprocessing (after-development) behavior of a novel photosensitive material, dichromate-sensitized pullulan (DCP), are investigated. The exposure mechanism and possibilities for controlling holographic grating properties are discussed. We have shown that it is possible to maximize the diffraction efficiency of interference gratings after development by controlling diffraction efficiency in real time. Stronger real-time effects of DCP compared with those of dichromated gelatin are achieved.     

Experimental immunotherapy of mice with transplanted MC-rhabdomyosarcoma resistant to doxorubicin

AIM: To compare the sensitivity of doxorubicin (DOX) sensitive and DOX-resistant MC-rhabdomyosarcoma (MC-RMS) cells to the action of lymphokine-activated cells (LAC). RESULTS: In vitro investigations showed that LAC received from the fraction of adherent lymphocytes possess the highest activity against DOX-resistant tumor cells, and LAC from lymphocytes of total pool--against DOX-resistant tumor cells pretreated with DOX at a low dose. Adoptive immunotherapy of MC-RMS in vivo showed the highest efficacy in the cases of LAC intratumoral injection and the one combined with intraperitoneal administration of DOX at a low dose (increase of survival time by 14% and 25%, respectively). CONCLUSION: Adoptive in vivo therapy of DOX-resistant Mh-RMS is effective if LAC or their combination with DOX at a low dose are administered.     

Test of the FDTD accuracy in the analysis of the scattering resonances associated with high-Q whispering-gallery modes of a circular cylinder

Our objective is the assessment of the accuracy of a conventional finite-difference time-domain (FDTD) code in the computation of the near- and far-field scattering characteristics of a circular dielectric cylinder. We excite the cylinder with an electric or magnetic line current and demonstrate the failure of the two-dimensional FDTD algorithm to accurately characterize the emission rate and the field patterns near high-Q whispering-gallery-mode resonances. This is proven by comparison with the exact series solutions. The computational errors in the emission rate are then studied at the resonances still detectable with FDTD, i.e., having Q-factors up to 10(3).     

Photonic-plasmonic scattering resonances in deterministic aperiodic structures

In this paper, we combine experimental dark-field scattering spectroscopy and accurate electrodynamics calculations to investigate the scattering properties of two-dimensional plasmonic lattices based on the concept of aperiodic order. In particular, by discussing visible light scattering from periodic, Fibonacci, Thue-Morse and Rudin-Shapiro lattices fabricated by electron-beam lithography on transparent quartz substrates, we demonstrate that deterministic aperiodic Au nanoparticle arrays give rise to broad plasmonic resonances spanning the entire visible spectrum. In addition, we show that far-field diffractive coupling is responsible for the formation of characteristic photonic-plasmonic scattering modes in aperiodic arrays of metal nanoparticles. Accurate scattering simulations based on the generalized Mie theory approach support our experimental results. The possibility of engineering complex metal nanoparticle arrays with distinctive plasmonic resonances extending across the entire visible spectrum can have a significant impact on the design and fabrication of novel nanodevices based on broadband plasmonic enhancement.     

Bridging crack model for fracture of spruce

An analysis is presented of how cracking in wood can be predicted using fracture mechanics. In situ, real-time, scanning electron microscopy was used as a tool to estimate the physical mechanism of fracture in softwoods using end-tapered double cantilever beam specimens. It was found that bridging behind the crack tip is the main toughening mechanism, which contributes to non-linear wood behavior in the presence of stress concentrations. A new bridging crack model is presented that mimics the observed cracking mechanism. Intrinsic flaw size is found to correspond to the fiber length of spruce.     

Biodegradable Self‐Folding Polymer Films with Controlled Thermo‐Triggered Folding

Self‐folding films are a unique kind of thin film. They are able to deform in response to a change in environmental conditions or internal stress and form complex 3D structures. They are very promising candidates for the design of bioscaffolds, which resemble different kinds of biological tissues. In this paper, a very simple and cheap approach for the fabrication of fully biodegradable and biocompatible self‐rolled tubes is reported. The tubes' folding can be triggered by temperature. A bilayer approach is used, where one component is active and another one is passive. The passive one can be any biocompatible, biodegradable, hydrophobic polymer. Gelatin is used as an active component: it allows the design of (i) self‐folding polymer films, which fold at room temperature (22 °C) and irreversibly unfold at 37 °C, and (ii) films, which are unfolded at room temperature (22 °C), but irreversibly fold at 37 °C. The possibilities of encapsulation of neural stem cells are also demonstrated using self‐folded tubes.     

Determination of the allowable graphite amount of a composite electrode for an electric arc furnace

Distribution of heat loads along the length and perimeter of electrodes in terms of the nominal power of transformer, optical characteristics of surfaces taking part in heat exchange and geometric dimensions of the furnace and electrodes has been obtained on the basis of mathematical simulation of processes of heat transfer in working volume of an electric arc furnace, the screening of radiation by electrodes being taken into account. The results obtained give an opportunity of determining the minimal permissible length of the composite electrode graphite part for furnaces with various nominal power transformers. The minimal permissible length of electrode-consumed graphite part is in the range of 80–100 cm for an 100-t electric arc furnace with the transformer of nominal power equal to 75 or 90 MVA. Decrease of the length of electrode graphite part will lead to damage of cooled metal part due to water burn-out.