Dejan Pantelić

Plasma diagnostics of the Grimm-type glow discharge

Abstract Results of argon-hydrogen plasma diagnostics in the plane cathode Grimm-type glow discharge are presented. Radial distributions of electron excitation temperatures, electron density and temperature of excited hydrogen atoms are reported. A numerical procedure necessary for the evaluation of the electron density and the temperature of excited hydrogen atoms from the profiles of hydrogen Balmer lines has been developed. The algorithm can be applied to the sum of an arbitrary line profile if they are convolved with a Gaussian profile.

Improving the holographic sensitivity of dichromated gelatin in the blue–green part of the spectrum by sensitization with xanthene dyes

The holographic properties of dichromated gelatin (DCG) sensitized with various xanthene dyes were studied, and results are reported. The sensitivity of dyed DCG in the green part of the spectrum compared with that of pure DCG (215 mJ/cm(2)) was significantly improved by addition of Rhodamine 6G (140 mJ/cm(2)) or Erythrosin B (90 mJ/cm(2)). Diffraction gratings were recorded with a He-Ne laser at 543.5 nm. The maximum diffraction efficiency was found to be 32% at normal incidence of the readout beam; it was 80% at the Bragg angle.

Protective effect of autophagy in laser-induced glioma cell death in vitro.

Laser phototherapy could be potentially used for cancer treatment, but the mechanisms of laser‐induced cell death are not completely understood. Autophagy is the process in which the damaged cellular proteins and organelles are engulfed by and destroyed in acidified multiple‐membrane vesicles. The aim of the present study was to investigate the role of autophagy in laser‐induced tumor cell death in vitro.

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.

High angular and spectral selectivity of purple emperor (Lepidoptera: Apatura iris and A. ilia) butterfly wings

The iridescent features of the butterfly species Apatura iris (Linnaeus, 1758) and A. ilia (Denis & Schiffermüller, 1775) were studied. We recognized the structural color of scales only on the dorsal side of both the fore and hind wings of males of both of the aforementioned butterfly species. The scale dimensions and microstructure were analyzed by a scanning electron microscope (SEM) and transmission electron microscope (TEM). The optical properties were measured and it was found that the peak reflectivity is around 380 nm, with a spectral width (full width at half maximum) of approximately 50 nm in both species. The angular selectivity is high and a purple iridescent color is observed within the angular range of only 18 degrees in both species.

Dichromated pullulan as a novel photosensitive holographic material

We found that pullulan [an a -glucan with (1?4) and (1?6) linkages] doped with chromium ions posseses promising holographic properties. It is environmentally stable and is capable of registering high spatial frequencies (as many as 1500 lines/mm) and producing surface relief. At 1000 lines/mm pullulans diffraction efficiency was 4%. Chemical treatment of pullulan with a mixture of water and isopropyl alcohol is simple. However, as expected from analogy with dichromated gelatin, pullulan is sensitive in only the blue-green region of the spectrum.

Dichromated pullulan diffraction gratings: influence of environmental conditions and storage time on their properties

Investigations of the environmental stability of diffraction gratings, recorded in dichromated pullulan (DCP), are reported. Profile changes of DCP surface relief gratings, under high humidity conditions, were analyzed using an atomic force microscope. It was found that the profile was not altered, while the diffraction efficiency was preserved. The influence of storage life on the diffraction efficiency and surface profile of DCP gratings were also investigated. It was concluded that DCP gratings offer much better stability compared with the dichromated gelatin.

Relief hologram replication using a dental composite as an embossing tool

A simplified method for holographic embossing tool production is presented. Surface relief diffraction gratings are holographically recorded in pullulan sensitized with ammonium dichromate (DCP). The surface structure is copied into dental photopolymer composite by direct contact and subsequent photo-polymerization. It was found that arbitrary surface micropattern can be replicated. Due to its excellent mechanical and thermal properties, micro-patterned dental composite can be further used as an embossing tool for mass production of holograms.

Single-beam, dual-view digital holographic interferometry for biomechanical strain measurements of biological objects.

Abstract. We describe a method for dual-view biomechanical strain measurements of highly asymmetrical biological objects, like teeth or bones. By using a spherical mirror, we were able to simultaneously record a digital hologram of the object itself and the mirror image of its (otherwise invisible) rear side. A single laser beam was sufficient to illuminate both sides of the object, and to provide a reference beam. As a result, the system was mechanically very stable, enabling long exposure times (up to 2 min) without the need for vibration isolation. The setup is simple to construct and adjust, and can be used to interferometrically observe any object that is smaller than the mirror diameter. Parallel data processing on a CUDA-enabled (compute unified device architecture) graphics card was used to reconstruct digital holograms and to further correct image distortion. We used the setup to measure the deformation of a tooth due to mastication forces. The finite-element method was used to compare experimental results and theoretical predictions.

Real-time measurement of internal stress of dental tissue using holography.

We describe a real-time holographic technique used to observe dental contraction due to photo-polymerization of dental filling during LED lamp illumination. An off-axis setup was used, with wet in-situ processing of the holographic plate, and consequent recording of interference fringes using CCD camera. Finite elements method was used to calculate internal stress of dental tissue, corresponding to experimentally measured deformation. A technique enables selection of preferred illumination method with reduced polymerization contraction. As a consequence, durability of dental filling might be significantly improved.