Mechanism of acid hydrolysis of N-acetyl-D-glucosamine

The hydrolysis kinetics of the chitin monomer, N-acetyl-D-glucosamine, in HCl, HClO₄, and H₃PO₄ was studied in relation to the acid concentration. The rate constants of N-acetyl-D-glucosamine deacetylation and D(+)-glucosamine formation in HClO₄ and H₃PO₄ were determined for the first time. The rate of the acetamide bond hydrolysis in N-acetyl-D-glucosamine depends on the concentrations of hydrogen ions and water. The nucleophilicity of the acid residues does not affect the rate of N-acetyl-D-glucosamine hydrolysis.     

Polarographic behavior of 2,4-dinitrochlorobenzene and products of its reduction

Polarographic behavior of 2,4-dinitrobenzene and products of its reduction, 2-chloro-5-nitroaniline and 4-chloro-3-nitroaniline, is studied: it is shown that formation of the corresponding chloronitroanilines in the case of polarographic reduction of 2,4-dinitrochlorobenzene is rather problematic. 0.1 M NaOH is recommended as the supporting solution for analytical control of conversion of 2,4-dinitrochlorobenzene and a mixture of 2-chloro-5-nitroaniline and 4-chloro-3-nitroaniline in reaction solutions obtained by preparative electroreduction of 2,4-dinitrochlorobenzene.     

Effect of ionic liquids on the extraction of americium by diphenyl (dibutyl) carbamoylmethyl phosphine oxide in dichloroethane from nitric acid solutions

The present paper demonstrates that room temperature ionic liquids (RTIL) added at 1–5 wt% to a diphenyl (dibutyl) carbamoylmethylphosphine oxide (Ph₂Bu₂) solution increase the extraction coefficients of americium from nitric acid by more than two orders of magnitude. Moreover, the use of the RTIL—1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide makes the extraction possible even from 8 M HNO₃. This is an important attribute of such extraction system from the point of its possible application for radiochemical analysis of technological samples and environmental solutions, since many methods are based on transferring the solid samples into an 8 M HNO₃ solution. The extraction data obtained revealed that three Ph₂Bu₂ ligands are included into the coordination sphere of americium, two of which represent a compound with the nitrate anion and one with the RTIL anion.     

Electrodeposition of americium on the stainless steel support for the purpose of radiochemical assay

The kinetics of uranium, plutonium and americium electrodeposition on steel targets from organic solutions of diphenyl-(N,N-dibutyl) carbamoylmethylphosphine oxide supplemented with the ionic liquid of trihexyltetradecylphosphonium hexafluorophosphate ([PH₄]⁺PF₆ ^?) in ethanol or N,N-dimethylformamide has been studied. When running a process in a dimethylformamide medium, and 0.05 M concentration of [PH₄]⁺PF₆ ^? americium deposition degree exceeds 95 % at the electrolysis time of 2 h. Alpha-spectra resolution of obtained target does not exceed 40 keV.     

Transverse field effect in graphene ribbons

It is shown that a graphene ribbon, a ballistic strip of carbon monolayer, may serve as a quantum wire whose electronic properties can be continuously and reversibly controlled by an externally applied transverse voltage. The electron bands of armchair-edge ribbons undergo dramatic transformations: The Fermi surface fractures, Fermi velocity and effective mass change sign, and excitation gaps are reduced by the transverse field. These effects are manifest in the conductance plateaus, van Hove singularities, thermopower, and activated transport. The control over one-dimensional bands may help enhance effects of electron correlations, and be utilized in device applications.     

Study of K^ - \to \pi ^0 e^ - \overline \nu _e \gamma decay with ISTRA+ setup

Results of study of the $K^ - \to \pi ^0 e^ - \overline \nu \gamma $ decay at the ISTRA+ setup are presented. We observed 4476 events of this decay. The branching ratio is found to be $R = \frac{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e \gamma )}}{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e )}}$ = (1.81±0.03(stat.)±0.07(syst.)) × 10^?2 for E*_γ > 10 MeV and θ*_eγ > 10°. For comparison with the previous experiment the branching ratio with cuts E*_γ > 10 MeV, 0.6 < cos θ*_eγ < 0.9 is calculated: R = $\frac{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e \gamma )}}{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e )}}$ = (0.47±0.02(stat.) ± 0.03(syst.)) × 10^?2. For the cuts E*_γ > 30 MeV and θ*_eγ > 20°, used in most theoretical papers, Br = (3.06 ± 0.09(stat.) ± 0.14(syst.)) × 10^?4. For the asymmetry we get A _ξ = ?0.015 ± 0.021. At present it is the best estimate of this asymmetry.     

Metastable modifications in mercury diiodide nanocrystals

The formation of the HgI₂ crystalline phase in pores of various porous matrices and on their surfaces was studied. Based on the analysis of the evolution of the HgI₂ optical spectra and electron and atomicforce microscopy data, it was shown that the formation of microcrystals of the stable red α modification is preceded by the formation and growth of particles of metastable yellow (β′) and orange modifications. The absorption edge of the β′ phase at T = 77 K is formed by excitonic transitions with an energy of ～2.7 eV. The Raman spectra of the β′ phase were compared to the spectra of known metastable yellow modifications.     

Transfer Hydrogenation of Ketones Catalyzed by Surface‐Active Ruthenium and Rhodium Complexes in Water

An improved, high‐yield, one‐pot synthetic procedure for water‐soluble ligands functionalized with trialkyl ammonium side groups H₂N(CH₂)₂NHSO₂‐p‐C₆H₄CH₂[NMe₂(C_nH_2n+1)]⁺ ( [HL ⁿ ]⁺ ; n=8, 16) was developed. The corresponding new surface‐active complexes [(p‐cymene)RuCl( L ⁿ )] and [Cp*RhCl( L ⁿ )] (Cp*=η⁵‐C₅Me₅) were prepared and characterized. For n=16 micelles are formed in water at concentrations as low as 0.6 mM , as demonstrated by surface‐tension measurements. The complexes were used for catalytic transfer hydrogenation of ketones with formate in water. Highly active catalyst systems were obtained in the case of complexes bearing C₁₆ tails due to their ability to be adsorbed at the water/substrate interface. The scope of these catalyst systems in aqueous solutions was extended from partially water soluble aryl alkyl ketones (acetophenone, butyrophenone) to hydrophobic dialkyl ketones (2‐dodecanone).     

Multiscale Simulation of Acid Treatment in a Carbonate Reservoir

Fluid Dynamics - The problem of acid treatment in carbonate reservoirs at different scales is considered. The problem of two-phase multicomponent Darcy flow through a porous medium with chemical...     

EFATOM two-detector one-photon emission gamma tomograph

The EFATOM two-detector one-photon emission computer tomograph, which is intended for radionuclide diagnostics of the internal organs and systems in the human body, has been designed and tested. A schematic diagram of its software package and detection units is represented. The results of its technical tests are presented. The characteristics of the EFATOM gamma tomograph are compared with its foreign analogs.