Mössbauer study of surface layers of high-speed steel after laser treatment

Mossbauer measurements in the backscattering geometry have been employed to determine an effect of the laser pulse duration on phase transformations and tungsten redistribution in the laser-affected area in the Tl high-speed steel. It has been found that after laser processing in the surface layer 10 μm thick the phase composition becomes homogeneous, the quantity of the retained austenite decreases with the rise in the laser pulse duration, the solid solution as a result of partial solution of carbides is saturated with tungsten up to 10 and 14 percent, the pulse durations being 1.2 and 6.0 ms respectively.     

Effect of conductive screens on the stabilization of plasma channels with currents of hundreds kAmps

Based on experimental data, we analyzed the results of the influence of external conductive shield on stabilization of plasma channels in high-power pseudospark switches—thyratrons TDI-type. Both no-ferrous and ferrous shields are tested. The research is a part of a work on improvement of switching capabilities of thyratrons capable of transferring currents up to hundreds kA with switching energy more than 50 kJ.     

“Natural” and “Technical” Shapes of the Bispectral Peak of a Triharmonic Oscillation

By analogy with the spectral-line profile characterizing the stability of a single quasi-harmonic oscillation, we study physical limits of stability and phase synchronism of a triharmonic oscillation (triplet) characterized by the shape of its bispectral peak. The triplet is the standard (test) signal for new-generation radiophysical devices, i.e., bispectral analyzers as well as the elementary component of highly informative bispectral signals. The problem of natural and technical shapes of the bispectral peak is analyzed. Bispectral analogs of the natural and technical broadening of spectral lines of self-oscillations with physically determined fluctuations of the component frequencies are proposed. It is shown that these characteristics can be observed and measured simultaneously. Universal shapes of three-dimensional bispectral peaks for extremely slow and extremely fast fluctuations, exponentially correlated fluctuations, and 1/f frequency fluctuations are found. The phenomenon of bispectral-peak superlocalization is analyzed. The obtained peak shapes and their effective cross-sectional areas characterize the ultimate attainable resolution of bispectral analyzers and information capacity of the synthesized bispectral structures.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 2, pp. 159–179, February 2005     

Synthesis of laminaribiose derivatives

Conclusions Some laminaribiose derivatives were synthesized by the ortho ester method and their structure was proved.     

Coumarinyl(thienyl)thiazoles as new fluorescent molecular photoswitches

A number of new photochromic 3-(4-phenylthiazol-5-yl)-and 3-(4-hetarylthiazol-5-yl)- coumarins has been synthesized. These compounds possess properties of molecular photo- switches providing a reversible change of the fluorescence intensity in the visible region of the spectrum upon alternating irradiation of their solutions with the visible and UV light. Irradiation with the UV light (λ < 400 nm) leads to their electrocyclization and loss of fluorescence, whereas irradiation of the cyclic form with the visible light (λ < 400 nm) returns the system to the state with the original absorption and fluorescence spectra. Switching of fluorescence is also observed in polymer matrices.     

Quantifying uncertainty in the measurement of arsenic in suspended particulate matter by Atomic Absorption Spectrometry with hydride generator

Arsenic is the toxic element, which creates several problems in human being specially when inhaled through air. So the accurate and precise measurement of arsenic in suspended particulate matter (SPM) is of prime importance as it gives information about the level of toxicity in the environment, and preventive measures could be taken in the effective areas. Quality assurance is equally important in the measurement of arsenic in SPM samples before making any decision. The quality and reliability of the data of such volatile elements depends upon the measurement of uncertainty of each step involved from sampling to analysis. The analytical results quantifying uncertainty gives a measure of the confidence level of the concerned laboratory. So the main objective of this study was to determine arsenic content in SPM samples with uncertainty budget and to find out various potential sources of uncertainty, which affects the results. Keeping these facts, we have selected seven diverse sites of Delhi (National Capital of India) for quantification of arsenic content in SPM samples with uncertainty budget following sampling by HVS to analysis by Atomic Absorption Spectrometer-Hydride Generator (AAS-HG). In the measurement of arsenic in SPM samples so many steps are involved from sampling to final result and we have considered various potential sources of uncertainties. The calculation of uncertainty is based on ISO/IEC17025: 2005 document and EURACHEM guideline. It has been found that the final results mostly depend on the uncertainty in measurement mainly due to repeatability, final volume prepared for analysis, weighing balance and sampling by HVS. After the analysis of data of seven diverse sites of Delhi, it has been concluded that during the period from 31^st Jan. 2008 to 7^th Feb. 2008 the arsenic concentration varies from 1.44 ± 0.25 to 5.58 ± 0.55 ng/m³ with 95% confidence level (k = 2).