New indicator reactions involving sulfur-containing organic compounds for the kinetic determination of selenium

New indicator reactions were proposed for the determination of selenium by the kinetic method based on the reduction of Methylene Blue by some sulfur-containing organic compounds. It was demonstrated that a high sensitivity of the determination of selenium is attained using unithiol and thiomalic, 2,3-dithiomercaptopropionic, and rubeanic acids as reducing agents. In the presence of unithiol, down to 4 ng/mL selenium can be determined. © 2001 MAIK "Nauka/Interperiodica"

Electrochemical Biosensors Based on Native DNA and Nanosized Mediator for the Detection of Anthracycline Preparations

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. A novel electrochemical DNA-sensor based on glassy carbon electrode (GCE) modified with electropolymerized Neutral red (NR) and polycarboxylated thiacax[4]arene with covalently attached mediator and electrostatically adsorbed DNA was developed for sensitive detection of anthracycline preparations. Intercalation of doxorubicin, daunorubicin and idarubicin into DNA increases the charge transfer resistance and decreases the electron exchange resulted in decay of the cathodic peak of NR reduction. The DNA-sensor developed makes it possible to determine down to 0.05nM doxorubicin, o.1nM doxorubicin and 0.5nM idarubicin. The DNA-sensor was tested on detection of doxorubicin in pharmaceuticals and artificial blood plasma with 95-100% recovery

Development of radial-shear rolling mill special stands for continuous cast billets deformation

The article offers the structure of the three-roll stand for radial-shear rolling that is designed to deformation of continuous cast billets. The stand can be installed in the pipe rolling mill manufacturing line that shall ensure manufacturing flexibility. To achieve the objective set, elaboration of working rolls integration with the drive as well as verification against the allowable torque and strength calculations in SolidWorks Simulation were performed at the design stage. For the major part of the frame, stresses do not exceed 60 MPa and the design rigidity rate will be 2.86 MN/mm. The special stand has a specific frame structure to ensure its mounting on the existing equipment base. The configuration of rolls sets is selected considering the possibility of integration with the spindle assemblies of the group drive and maximum allowable cross angle (≤ 15 ). The developed design proves to have sufficient strength margin with the relatively small weight. The special radial-shear rolling mill stand will allow increasing total strain degree and reducing the number of billets sizes. © Published under licence by IOP Publishing Ltd

Reaction of 2,3-dimethylmercaptopropionic acid with methylene blue as an indicator reaction for the kinetic determination of selenium

A new indicator reaction between 2,3-dimethylmercaptopropionic acid and Methyl Blue was proposed for the kinetic determination of selenium. The optimal reaction conditions were found. A linear relationship was observed between the induction period and the Se(IV) concentration in the range between 0.9 and 9.6 ng/mL Se. Masking with EDTA and solvent extraction with diethyldithiophosphoric acid can be used for the separation of interfering elements forming complexes with the reagent. © 2001 MAIK "Nauka/Interperiodica"

Comparative assessment of electrochemical biosensors for determining inhibitors - Environmental pollutants

Electrochemical biosensors are developed on the basis of pH and carbon-paste electrodes with replaceable cholinesterase membranes supported on paper or polymeric membranes (Nylon, Hybond, Amersham and cellulose nitrate, Sartorius). Biosensors provide the rapid determination of Diazinon, Fozolone, Metaphos, and Koral with a detection limit of n × (10-8 to 10-9) M. The analytical characteristics of pesticide determination vary with the membrane material, which is due to the adsorption of the inhibitor on the membrane surface and depends on the hydrophobicity of the membrane material and the inhibitor. The modification of the biosensor sensitivity to pesticides on the addition of surfactants was studied, and the mechanism of biosensor response to inhibitors of various nature was investigated in both batch and flow-injection modes. © 1999 MAHK "Hayka/Interperiodica"

MODERNIZATION OF THE KHARKIV MICROWAVE SPECTROMETER: CURRENT STATE

Subject and Purpose. Results are presented of the recent considerable upgrade implemented at the Kharkiv microwave spectrometer. The upgrade has been aimed at extending the operating frequency range and increasing the utmost accessible spectral resolution of the spectrometer. Methods and Methodology. In order to extend the frequency range we have designed and constructed new BWO-based oscillator units, also providing for possibility of frequency tripler application. Construction of a new absorbing cell of enlarged diameter allowed us to considerably improve the spectral resolution for Lamb-dip measurements. Results. Owing to the upgrade, the spectrometer has become able to cover the frequency range from 34 to 420 GHz, with a gap from 183 to 200 GHz. The spectral resolution in the Lamb-dip observation mode has been increased by a factor of two. In addition, the functionality of the spectrometer has been significantly improved via modernization of several of its subsystems. Conclusions. The new upgrades of the spectrometer systems have permitted extending the operational frequency range and increasing the utmost accessible resolution by means of reducing the time-of-flight line broadening in the Lamb-dip measurements. In addition, application of square-wave frequency modulation with accurately known modulation parameters, in combination with careful modeling of the distortions caused by reflections in the absorbing cell, has allowed us to significantly improve the accuracy of line frequency measurements

Flow-injection systems for determining iron(III) and iodide with the use of catalytic reactions

Flow-injection systems with spectrophotometric detection were developed on the basic of catalytic reactions, namely, the Fe(III)-catalyzed oxidation of methanol with hydrogen peroxide and the iodide-catalyzed cerium-arsenite reaction. The developed systems were used to analyze industrial and natural waters. The detection limits attained were as low as 0.02 μg/mL of Fe(III) and 0.2 μg/mL of I- at relative standard deviations of 2-7% with the throughoutput of 35 and 25 h-1, respectively. © 1997 MAEe cyrillic signK Hayκa/Interperiodica Publishing

Affinity biosensors based on disposable screen-printed electrodes modified with DNA

Simple and sensitive DNA sensors have been developed on a base on graphite screen-printed electrodes modified with DNA and enzymes. Cholinesterase and peroxidase immobilized by treatment with glutaraldehyde were used for the detection of human DNA antibodies of systemic lupus erythematosus and bronchial asthma patients. The amperometric signal was measured at +680mV versus Ag/AgCl for DNA-cholinesterase sensor and -150mV for DNA-peroxidase sensor 5min after the injection of acethylthiocholine and hydroquinone, respectively. The addition of serum samples results in the sharp decrease of the signal due to the formation of DNA-antibody adducts followed by the suppression of the access of substrate to the enzyme active site. Sulfonamide medicines suppress the DNA-antibody interaction due to the competitive binding along DNA minor grooves. DNA sensor labeled with peroxidase showed the linear calibration range of 5×10-9 to 7×10-5moll-1 of sulfamethoxazole and of 5×10-8 to 1×10-4moll-1 of sulfathiazole. © 2002 Elsevier Science B.V. All rights reserved

New data on fauna and flora of the Upper Paleozoic deposits of the North Siberian platform (Anabar-Khatanga Saddle)

© 2015, Pleiades Publishing, Ltd. Core hole no. AKh-1 has been drilled within the Anabar-Khatanga oil and gas fields, on the left bank of Khatanga Bay. To date only data on the upper 972.5 meters of the core have been examined in detail and processed by the authors; however, we obtained unique materials displaying lithoand biostratigraphic features of the section of Permian deposits. In the explored part of Permian deposits we can very clearly distinguish the top of the Tustakh Formation and the Lower and Upper Kozhevnikova formations. The assemblages of flora, foraminifers, brachiopods, marine and nonmarine bivalves are characterized and results of palynological analysis are presented