ParaHydrogen Polarized Ethyl-[1-13C]pyruvate in Water,a Key Substrate for Fostering the PHIP-SAH Approach to Metabolic Imaging

An efficient synthesis of vinyl-[1-¹³C]pyruvate has been reported, from which ¹³C hyperpolarized (HP) ethyl-[1-¹³C]pyruvate has been obtained by means of ParaHydrogen Induced Polarization (PHIP). Due to the intrinsic lability of pyruvate, which leads quickly to degradation of the reaction mixture even under mild reaction conditions, the vinyl-ester has been synthesized through the intermediacy of a more stable ketal derivative. ¹³C and ¹H hyperpolarizations of ethyl-[1-¹³C]pyruvate, hydrogenated using ParaHydrogen, have been compared to those observed on the more widely used allyl-derivative. It has been demonstrated that the spin order transfer from ParaHydrogen protons to ¹³C, is more efficient on the ethyl than on the allyl-esterdue to the larger J-couplings involved. The main requirements needed for the biological application of this HP product have been met, i. e. an aqueous solution of the product at high concentration (40 mM) with a good ¹³C polarization level (4.8 %) has been obtained. The in vitro metabolic transformation of the HP ethyl-[1-¹³C]pyruvate, catalyzed by an esterase, has been observed. This substrate appears to be a good candidate for in vivo metabolic investigations using PHIP hyperpolarized probes.     

Development of Ion Detector Based on Low-Pressure Time Projection Chamber for Accelerator Mass Spectrometry

Physics of Atomic Nuclei - A new ion identification method for accelerator mass spectrometry on the basis of measuring ion track ranges is proposed. A low pressure time projection chamber (TPC)...     

A regularized method for solving constrained pseudoinverse problems

For a constrained pseudoinverse problem whose operators satisfy the complementarity condition we propose a one-parameter continuous regularization method of the second order. This method is based on stabilization of solutions to Cauchy problems for a linear differential equation of the second order in a Hilbert space which is obtained from the heavy ball method. We establish requirements to the parametric regularization function and perturbation levels that ensure the stability of the method in the class of all possible bounded perturbations.     

Influence of the bilayer thickness of nanostructured multilayer MoN/CrN coating on its microstructure,hardness, and elemental composition

Multilayer nanostructured coatings consisting of alternating MoN and CrN layers were obtained by vacuum cathode evaporation under various conditions of deposition. The transition from micron sizes of bilayers to the nanometer scale in the coatings under investigation leads to an increase in hardness from 15 to 35.5 GPa (with a layer thickness of about 35 nm). At the same time, when the number of bilayers in the coating decreases, the average Vickers hardness increases from 1267 HV_0.05 to 3307 HV_0.05. An increase in the value of the potential supplied to the substrate from–20 to–150 V leads to the formation of growth textures in coating layers with the [100] axis, and to an increase in the intensity of reflections with increasing bilayer thickness. Elemental analysis carried out with the help of Rutherford backscattering, secondary ion mass spectrometry and energy dispersion spectra showed a good separation of the MoN and CrN layers near the surface of the coatings.     

Synthesis of hyperbranched polyester polymaleic acids third generation

The third generation hyperbranched polyesterpolyol has been modified with maleic anhydride at various ratios of the polyol to the modifying agent, from 1: 6 to 1: 18. The prepared modified polyols are capable of the complex formation with copper(II), cobalt(II), and nickel(II) ions.     

Conditions for the solvability of boundary value problems for quasi-elliptic systems in a half-space

We consider boundary value problems in a half-space for a class of quasi-elliptic systems with constant coefficients. We assume that the boundary value problems satisfy the Lopatinskii condition. We obtain necessary and sufficient conditions for their unique solvability in Sobolev spaces.     

Submanifolds of compact operators with fixed multiplicities of eigenvalues

For the first time, a manifold of symmetric real matrices with fixed multiplicities of eigenvalues was considered by Arnold. In the case of compact real self-adjoint operators, similar results were obtained by Japanese mathematicians Fujiwara, Tanikawa, and Yukita. They introduced a special local diffeomorphism “straightening” the Arnold manifold. Later, the properties of the indicated diffeomorphism were studied by Dymarskii. We describe the smooth structure of submanifolds of finite-dimensional and compact operators of the general form in which a selected eigenvalue is associated with a single Jordan block.     

An IR spectroscopic study of acid centers on the surface of Al,Zr silica gels

Acid centers of Al, Zr silica gels with approximately equal aluminum ion contents (∼2.4% Al₂O₃) and various concentrations of Zr ions were studied by IR spectroscopy using the deuteroacetonitrile molecule as a probe. The surface of such samples was found to contain Lewis acid centers of two types, coordination unsaturated (I) silicon and (II) zirconium ions. An increase in the content of zirconium ions was accompanied by a decrease in the intensity of the 2328 cm⁻¹ band in the IR spectra. This band was characteristic of interaction of CD₃CN with Lewis acid centers of type I. The suggestion was made that this was caused by a decrease in the accessibility of coordination unsaturated silicon ions to CD₃CN molecules.     

Activity study of graphite from the chernobyl NPP reactor

The content of the isotopes ³H, ¹⁴C, ³⁶Cl, ⁵⁵Fe, ⁵⁹Ni, ⁶³Ni, ⁶⁰Co, ⁹⁰Sr, ^93m Nb, ¹⁰⁸Ag, ¹³³Ba, ¹³⁴Cs, ¹³⁷Cs, ¹⁵⁴Eu, and ¹⁵⁵Eu in the GRP-2-125 graphite from the reactor of Power Unit 2 at the Chernobyl Nuclear Power Plant was measured. The results were compared with the calculations and literature data. Some regularities and correlations were revealed in the content of various radionuclides in graphite. Graphite porosity and desorption of radionuclides from graphite were studied. Original Russian Text ? M.D. Bondar’kov, D.M. Bondar’kov, A.M. Maksimenko, V.A. Zheltonozhskii, M.V. Zheltonozhskaya, V.V. Petrov, A.I. Savin, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 2, pp. 274–278.     

Mathematical modeling of extension of an inhomogeneous elastic cloth

We propose mathematical models for a knitted fabric in tension that can be used to calculate the strain of the cloth thread from the properties of the cloth and the loads applied to the cloth. Under simplifying assumptions, the problem is reduced to consideration of an elementary cell of the cloth that contains a thread loop. The loop is first modeled by a thread oval with point forces and then by a plate with a hole under distributed loads. In strength analysis, this allows one to use methods of elasticity theory. A number of hypotheses are used to establish the relation between the stress state of the thread oval and the corresponding state of the plate, which makes it possible to model the mechanical behavior of a thread in the material in a variety of forms. The theoretical relationships obtained are compared to the experimental data available in the literature. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 5, pp. 227–238, September–October, 1999.