An electrochemical aptasensor for cytochrome C,based on pillar[5]arene modified with Neutral Red

An electrochemical aptasensor is developed for the highly sensitive determination of cytochrome C, using a change in the redox current of Neutral Red covalently bound to terminal carboxyl groups of decasubstituted pillar[5]arene as a signal. The inclusion of the analyte into the complex with an aptamer reduces peaks of redox current of the dye through the dissociation of electron transfer chain in the surface layer. The aptasensor enables the determination of 1 nM to 1.0 mM of cytochrome C in the presence of 1000-fold excesses of albumin, polyethylene glycol, and lysozyme as models of interfering components in biological fluids.     

Efficiency in a forced contribution threshold public good game

We contrast and compare three ways of predicting efficiency in a forced contribution threshold public good game. The three alternatives are based on ordinal potential, quantal response and impulse balance theory. We report an experiment designed to test the respective predictions and find that impulse balance gives the best predictions. A simple expression detailing when enforced contributions result in high or low efficiency is provided.     

On a convective flow of a binary mixture in a vertical layer

Under study is an invariant solution of the equations of thermal diffusive convection which describes a stationary process of a binary mixture flow in a vertical layer under the action of the pressure gradient and the buoyancy force that depends nonlinearly on temperature and concentration. Some general properties of this solution are established and an existence theorem is proved. Analysis of the numerical solution of the problem is carried out in the cases of a power-law and exponential dependence of the buoyancy force on its argument.     

Properties and structural state of the surface layer in a zirconium alloy modified by a pulsed electron beam and saturated by hydrogen

A pulsed action of an electron beam on a Zr-1% Nb zirconium alloy is studied. Alloy samples are irradiated by three 50-μs pulses at an energy density of 15–25 J/cm², a power of (3–6) × 10⁴ W/cm², a current density of 10–50 A/cm², and an electron energy of 18 keV. This method of processing is found to modify the surface layer of the alloy without changing the structure-phase state of its volume. This surface modification increases the hydrogen saturation resistance of the alloy.     

Choice of optimum conditions of emitter preparation for X-ray fluorescence analysis of aerosols

The nonuniformity of aerosol distribution over filter surface was studied. It was found that the distribution depends on the properties of the studied object and on the sampler type: particle concentration is often higher in the center of the filter, but in some cases, they shift to the edges; the uniform distribution of particles is observed rarely. It was shown that, if the emitter in X-ray fluorescence analysis (XRF) is a disk 3 cm in diameter cut from the center of a filter 5 cm in diameter, the systematic error of the results of analysis may be higher than 0.30. Recommendations on the choice of the conditions of sampling aerosols and emitter preparation are formulated. If these conditions are met, the results of XRF analysis of nonuniform filters are characterized by s_r = 0.05, which satisfies the admissible error.     

Synthesis and properties of derivatives of 2-mercaptobenzothiazole

2,3-Dihydro-4H-[1,3]-thlazino[2,3-b]benzothiazolium chlorides have been synthesized and their reduction with sodium borohydride has given previously-unknown derivatives of (perhydro-1,3-thiazino) [2,3-b]benzothiazoline. The stability of the compounds in acid and alkaline media has been studied.For part VII, see [1].     

Synthesis in the 2-mercaptobenzothiazole series

The reduction of some dihydrothiazolobenzothiazolium salts with sodium borohydride may take place in two directions: with the formation of thiazolidino[2, 3-b]benzathiazolines and with the cleavage of the C-S bond to give N-(-mercaptoethyl)benzothiazolines. The behavior of thiazolidino[2, 3-b]benzothiazoline under the conditions of acid and alkaline hydrolysis has been studied.For communication VI, see [1].     

Specifics of Interaction of Acetone Molecules with Quasi-free Electrons: Analysis of Positron Annihilation Characteristics in Aqueous and Alcoholic Acetone Solutions

The yields of formation of radiolytic hydrogen (H₂) and orthopositronium (o-Ps) in aqueous and alcoholic acetone solutions were experimentally determined. A decrease in the o-Ps yield with an increase in the acetone concentration is much weaker than the decline in the yield of solvated electrons (e^– _s) under picosecond pulse radiolysis conditions. In contrast, the decrease in the o-Ps yield is minimal in higher alcohols where the inhibiting action of acetone e^– _s is most pronounced. These findings seem to contradict the conventional concepts of Ps formation via the intratrack reaction of positron recombination with a track electron (e^–), which competes with the reaction of e^– scavenging by dissolved acetone molecules. This contradiction can be eliminated, assuming that the scavenging of e^– by acetone begins from the formation of the weakly bound transient state (CH₃)₂CO···e^– capable of donating e^– to a positron. This opens up an additional pathway for the formation of the Ps atom.     

The effective dipole moments of isobutyric acid in the liquid state and dilute solutions in methanol

The dipole moments of isobutyric acid (I) were determined in the liquid state (μ₁) and dilute solutions in methanol (μ₁) at 20–50°C. The permittivity of I in the liquid state was found to increase as the temperature grew, and the permittivity of solutions of I was lower than that of pure methanol; it decreased as the concentration of I and the temperature of solutions increased. The effective dipole moments of I were calculated using the Onsager polarization theory for the pure liquid and the Buckingham statistical polarization theory for solutions with various acid concentrations in methanol. The small μ₁ (～0.8 D) and higher μ₂ (～3.0 D) values compared with the dipole moment of I in the gas phase μ₀ (1.9 D) were analyzed as determined by the character of acid-acid, acid-solvent, and solvent-solvent intermolecular interactions, a key role in which was played by H-bonds. An analysis of the dipole moments of I in methanolic solutions led us to conclude that the μ₁ and μ₂ values corresponded to the dipole moments of associates and solvates comprising like and unlike molecules linked by intermolecular H-bonds. Their stoichiometry changed as the temperature increased.