Study of chemical composition of <Emphasis Type="Italic">Asparagus racemosus</Emphasis> roots

The chemical composition of Asparagus racemosus roots is studied by the methods of gas chromatography and high-performance liquid chromatography. Marker substances characteristic of this type of raw materials are revealed. The dioscin content in the roots of A. racemosus is quantitatively determined.     

Photonic-crystal fibers with a photonic band gap tunable within the range of 930–1030 nm

The physical principles of photonic-crystal fibers with a photonic band gap tunable in the visible and near-IR spectral ranges are demonstrated. Direct numerical integration of the Maxwell equations with the use of the finite-difference time-domain technique reveals the possibility of creating holey fibers with a photonic-crystal cladding whose photonic band gap lies within the frequency range characteristic of widespread solid-state femtosecond lasers. The fabrication of holey fibers with a pitch of the two-dimensional periodic structure of the cladding less than 500 nm allowed us to experimentally observe a photonic band gap in transmission spectra of holey fibers tunable within the range of 930–1030 nm. This photonic band gap is satisfactorily described within the framework of the proposed numerical approach based on the finite-difference time-domain method.     

Simultaneous determination of proteins in microstructured optical fibers supported by chemometric tools

Analytical and Bioanalytical Chemistry - A new perspective on the relevant problem—creating simple, rapid, and efficient protein sensors based on microstructured optical fibers using a simple...     

Spectral broadening of 40-fs Ti:sapphire laser pulses in photonic-molecule modes of a cobweb-microstructure fiber

Photonic-molecule modes of a cobweb-microstructure fiber allow efficient nonlinear optical spectral broadening of nanojoule femtosecond light pulses. Spectral widths of approximately 200 nm are achieved at the output of a 6-cm sample of such a fiber for 40-fs Ti:sapphire laser pulses with an energy of a few nanojoules coupled into photonic-molecule modes. Higher values of the group index and a lower group-velocity dispersion, attainable with higher-order photonic-molecule modes, allow the efficiency of spectral broadening of femtosecond laser pulses to be increased relative to the efficiency of spectral broadening in the fundamental photonic-molecule mode. Received: 9 June 2002 / Revised version: 29 June 2002 / Published online: 22 November 2002 RID="*" ID="*"Corresponding author. Fax: +7-095/939-3959, E-mail: zheltikov@top.phys.msu.su     

Composite Pt/(SnO2/C) and PtSnNi/C Catalysts for Oxygen Reduction and Alcohol Electrooxidation Reactions

Russian Journal of Electrochemistry - The electrodeposition of tin and tin-nickel on a highly dispersed carbon material is used to obtain composite supports. These composite supports were used in...     

Determination of glucose concentration in biological liquids using photonic crystal waveguides

The possibility of using hollow-core photonic crystal waveguides as biological sensors is shown. The influence of the glucose concentration in solutions introduced into the waveguide core on the transmission spectrum of photonic crystal waveguides is shown. Two possible methods of determining the glucose concentration in liquids are considered, refractometric and photometric.     

ALSV investigation of the phase composition of electrolytic Cu + Sn alloys

Anodic linear sweep voltammograms (ALSVs) have been recorded for thin layers of Cu + Sn alloys electrochemically deposited on graphite from a pyrophosphate bath. Three characteristic peaks were found. The first peak, appearing in the ALSVs of all samples, could be ascribed both to pure Cu (in the deposit obtained at low cathodic polarization) and to the η-Cu₆Sn₅ phase, while one of the other two peaks appearing only in the samples obtained at low cathodic polarization should reflect the presence of the -Cu₃Sn phase. The other peak, appearing only in the samples obtained at high cathodic polarization, is likely to reflect the presence of the tin-rich β-solid solution. The phase composition, in terms of the content of different phases, was determined as a function of the thickness of the alloy as well as of the deposition potential.     

Supercontinuum generation in a two-dimensional photonic kagome crystal

We demonstrate the generation of ultrabroad spectra in a photonic crystal fiber with a kagome-lattice transverse structure. This two-dimensional periodic photonic lattice allows for strong confinement of light without employing defect states nor using photonic bandgap guiding. Light guiding is mediated by total internal reflection in the intersections of the lattice structure, similar to tapered or micro-structured fibers. The kagome lattice structure is manufactured from a soft glass with a high nonlinearity. Using a Ti:sapphire oscillator as a pump source, we observe for the first time impressive supercontinuum generation in the guided modes of a 2D photonic lattice. Supercontinuum generation is caused by fission and radiation of higher-order solitons in the anomalous dispersion range. Our spectrum encompasses the spectral range from 200 to 1750 nm. The dependence of the continuum on coupling spot location, fiber length, and pump wavelength and power as well as on pulse duration and polarization state is investigated. Using a numerical simulation for the lattice structure, pulse propagation through this structure is theoretically studied. Our model reveals the mechanism of supercontinuuum generation in the 2D photonic structure and explains the essential experimental findings.Electronic supplementary material to this article is avaiable at and accessible for authorized users.     

Structural features of martensitic transformations upon the low-temperature deformation of metastable austenitic Fe-Cr-Ni alloy single crystals

The features of martensitic transformations upon the low-temperature (1.8–300 K) deformation of metastable Fe-18Cr-10Ni and Fe-18Cr-15Ni alloy single crystals with low stacking-fault energies were studied. It was shown that the γ → ɛ and γ → α martensitic transformations play the main role in increasing strength and plasticity when the deformation temperature is reduced to 4.2 K.     

SEM and XRF spectroscopy methods for studying and controlling the surface morphology of metal-polymer films

The surface morphology and the degree of porosity of metal-polymer films deposited by the electrolytic method are studied using scanning electron microscopy (SEM) and X-ray fluorescence (XRF) spectroscopy. Mathematical processing is performed, and the structure of the sample surfaces is analyzed using images obtained in the mode of secondary-electron recording. The volume-packing coefficients for heterogeneous coatings are determined using the XRF analysis data. The dependence of the surface structure and volume-packing coefficient of copper in the film on the polymer type and the coating thickness is established.