Phase diagram of the Pr–Mn–O system in composition–temperature–oxygen pressure coordinates

The phase relations in the Pr–Mn–O system were studied by the static method at lowered oxygen pressure in combination with thermal analysis and high-temperature X-ray diffraction. The equilibrium oxygen pressure in dissociation of PrMn₂O₅ and PrMnO₃ was measured, and the thermodynamic characteristics of formation of these compounds from elements were calculated. The Р–Т–х phase diagram of the Pr–Mn–O system was constructed in the “composition–oxygen pressure–temperature” coordinates.     

Loading capacities of monolithic capillary columns in gas chromatography

The loading capacities of monolithic capillary columns based on silica gel and divinylbenzene are studied for two carrier gases, CO₂ and N₂. It is shown that the efficiency of the column is more sensitive to the overload of the column than the retention time of the sorbate is, especially for the CO₂ carrier gas. It is established that the loading capacity of a monolithic column based on silica gel decreases significantly in going from N₂ to CO₂. For columns based on divinylbenzene, the loading capacity is found to be virtually the same for both carrier gases. For monolithic columns, the loading capacity per one meter of column length is found to be 10 and more times higher than that for a standard open capillary column.     

State of atoms of the transition group elements in dilute solid solutions based on LiMO2 (M = Sc, Ga, Al): II. Magnetic characteristics of nickel atoms in LiNi x Sc1 ? x O2 solid solutions

The state of nickel atoms in LiNi _x Sc_{1 − x} O₂ solid solutions was studied. The anomalous magnetic characteristics can be accounted for only by the presence of dilution-resistant clusters containing Ni(III) in two states: high- and low-spin. Original Russian Text ? A.A. Selyutin, N.P. Bobrysheva, N.V. Chezhina, A.V. Shchukarev, A.O. Kozin, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 10, pp. 1608–1612. For communication I, see [1].     

Spectra and structure for Bi0-BiCl3-Li,K/Cl

Raman-scattering, electronic-absorption, and ESR spectra have been used to determine the states of bismuth and the structures of the compounds formed in molten chloride systems; it is found that BiCl₄ ^– with T_d symmetry are formed in BiCl₃-Li, K/Cl_eu melts, while a Bi⁰-BiCl₃-Li, K/Cl_eu melt produces the BiCl₄ ^– BiCl₃ + Cl^–; BiCl₃ + Bi⁰ Bi₂Cl₃ equilibria with the formation of Cl^– the quasitetrahedral ion in the second stage, which has a metal-bond and a single unpaired electron.Institute for General and Inorganic Chemistry, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 3, pp. 311–315, May–June, 1991. Original article submitted September 12, 1988.     

Shpol'skii spectrometry, a distinct method in environmental analysis

Whereas common fluorescence and phosphorescence spectra of organic molecules in solutions show little details, Shpol'skii spectra exhibit completely resolved vibronic transitions, enabling the analytical distinction between isomeric compounds. In a simplified qualification, the Shpol'skii technique combines the sensitivity inherent to luminescence spectroscopy with the selectivity of infrared spectra. There are however two main limitations as far as its applicability is concerned: (i) cryogenic temperature conditions are required and (ii) the analytes should be compatible with the solvent matrix, typically an-alkane.The present paper is focused on the potential and achievements of Shpol'skii spectrometry in environmental analysis. After a discussion of the fundamental aspects of spectral line-broadenings and the approaches to accomplish high-resolution, special attention is paid to experimental and instrumental aspects. Recent instrumental developments have made Shpol'skii spectroscopy not only attractive for qualitative but also for quantitative purposes.The main part of the review is devoted to recent applications, for instance the determination of parent polycyclic aromatic hydrocarbons (PAHs) in complex environmental samples as crude oils, sediments, soils and biota. The special features of large PAHs, i.e. PAHs with seven or more hexagonal aromatic rings are considered separately. The analysis of PAH-metabolites in samples like fish bile and human urine is extensively discussed. Subsequently the applicability of Shpol'skii spectroscopy to both in-ring and atring substituted polycyclic aromatics is concerned, including amino- and nitro-substituted PAHs and nitrogen-, oxygen- and sulphur-heterocyclic compounds. The review ends with an interesting new development i.e. the Shpol'skii spectra of fullerenes, the soccerball and rugbyball shaped molecules C₆₀ and C₇₀, compounds receiving wide attention in physics and chemistry.     

Effect of the carrier gas pressure on the dynamic and separation characteristics of divinylbenzene-based monolithic capillary columns for gas chromatography

The efficiency and dynamic characteristics of divinylbenzene-based monolithic capillary columns for gas chromatography were analyzed using a test mixture composed of five light hydrocarbons. The chromatographic properties of these columns were evaluated within the framework of two varieties of the van Deemter equation, the classical one and that proposed by Giddings (with consideration given to the pressure drop across the column). An analysis of the van Deemter curves demonstrated that the main contribution to peak smearing comes from the diffusion processes in the mobile phase. The contribution from the resistance to mass transfer between the mobile and stationary phases is less important. Negative values obtained for A in the van Deemter equation and for C _s in the Giddings model, parameters that characterize the stationary phase structure and mass transfer kinetics in the stationary phase, have no physical meaning, a result calling for further studies of this type of monolithic capillary columns since the classical theory supposed these parameters to be strictly positive. Under optimal conditions, the HETP of the monolithic columns was found to be 3 to 4 times smaller than that typical of open capillary columns of the same diameter.     

Use of relaxation viscoelastic model in calculating uniaxial homogeneous strains and refining the interpolation equations for maxwellian viscosity

The work applies the relaxation viscoelastic model proposed in [1–3] for calculations of high-rate deformation of bars and plates and for refining the interpolation equations of Maxwellian viscosity χ (a magnitude inverse to the relaxation time τ of the tangential stresses) by means of them. These calculations were carried out to study the dependence of the dynamic yield limit σ_g on the deformation rate ?^·. The authors propose that the dependence σ_g(?, T) in ?^· be transformed, such that χ = ?^· (σ, T) (here σ is the intensity of the tangential stresses and T is temperature) in order to construct interpolation equations for Maxwellian viscosity χ. A numerical analysis demonstrated that this equation leads to the correct qualitative dependence in calculations of σ_g (?^·). A correction factor is introduced into the equation χ = χ(σ, T) in order for the numerical calculations to quantitatively coincide with the experimental data in this work.     

Supermetallization of peptides and proteins during electrospray ionization

The formation of metal‐peptide complexes during electrospray ionization (ESI) is a widely known phenomenon and is often considered to be undesirable. Such effect considerably limits the use of ESI mass spectrometry for the investigation of biologically relevant metal‐peptide compounds that are present in the solution and play critical roles in many bioprocesses such as progression of neurodegenerative diseases. In the article, it is demonstrated that under specific conditions such as high temperature of the desolvating capillary, an interesting effect, which can be called as ‘supermetallization’, occurs. Using a model peptide Αβ amyloid domain 1–16, it was observed that an increase in the temperature of the desolvating capillary results in multiple substitutions of hydrogen atoms by Zn atoms in this peptide. At high temperatures (T ~ 400 °C), up to 11 zinc atoms can be covalently bound to (1–16) Αβ. It was observed that supermetallization of (1–16) Αβ depends on the solvent composition and pH. Supermetallization was also demonstrated for proteins, such as ubiquitin and cytochrome C. That proves that the supermetallization is a general phenomenon for peptides and proteins. For the structural investigation of supermetallized complexes, electron‐capture dissociation (ECD) fragmentation was applied. The effect of hydrogen rearranging during ECD was observed. In addition, quantum chemical calculations were used to estimate the possible structures of different supermetallized complexes. These results allow a more deep understanding of the limitations of the use of ESI mass spectrometry for the investigation of biologically relevant metal‐peptide complexes. Copyright © 2015 John Wiley & Sons, Ltd.     

Stress-strain state of ice cover during aircraft takeoff and landing

We consider the linear unsteady motion of an IL-76TD aircraft on ice. Water is treated as an ideal incompressible liquid, and the liquid motion is considered potential. Ice cover is modeled by an initially unstressed uniform isotropic elastic plate, and the load exerted by the aircraft on the ice cover with consideration of the wing lift is modeled by regions of distributed pressure of variable intensity, arranged under the aircraft landing gear. The effect of the thickness and elastic modulus of the ice plate, takeoff and landing regimes on stress-strain state of the ice cover used as a runway.     

Motion of a slender body in a fluid under a floating plate

This paper studies the three-dimensional unsteady problem of the hydroelastic behavior of a floating infinite plate under the impact of waves generated by horizontal rectilinear motion of a slender solid in a fluid of infinite depth. An analytic solution of the problem is found based on the known solutions for the unsteady motion of a point source of mass in a fluid of infinite depth under a floating plate. Asymptotic formulas are obtained which model the motion of a solid slender body in a fluid by replacing the body with a source-sink system. These formulas are used to numerically analyze the effect of plate thickness, depth of the body, its dimensions and the velocity of rectilinear motion on the amplitude of deflection of the floating plate. The motion of a submarine under a nonbreakable plate was modeled experimentally. Theoretical and experimental data are in good agreement.