Technical facilities for improving the quality of irradiation of materials by ELV accelerators

Various pieces of equipment that improve the quality of irradiation at ELV accelerators are reviewed. This equipment includes two-way, four-way, and circular irradiation systems; a conveying unit; and systems for visualizing and monitoring the basic process variables. A method that provides for a highly uniform distribution of the linear dose rate is described.     

Refractive indices of K<Subscript>2</Subscript>ZnCl<Subscript>4</Subscript> crystals in an incommensurate phase under uniaxial stresses

The influence of uniaxial mechanical stresses directed along the principal crystallophysical axes on refractiveindex temperature dependences in K₂ZnCl₄ crystals was studied. It is established that the refractive indices ni are quite sensitive to uniaxial stresses. Significant baric shifts of the paraphase–incommensurate–commensurate phase transition points to different temperature regions were observed, which is due to the effect of the uniaxial stress on the K₂ZnCl₄ crystal structure. It is found that applying uniaxial pressure increases the value of the temperature hysteresis of the commensurate–incommensurate phase transition.     

A quantitative approach to low-energy quantum chromodynamics

A general method for solving the low-energy spectrum of an infrared unstable field theory is presented. The method involves a strong coupling expansion of the lattice approximation to the theory. Ultimately the results must be continued to zero-coupling constant in accord with the asymptotic freedom of such theories. The method is applied to the pure gauge field (glueball) part of quantum chromodynamics. The spectrum of lowest-lying states consists of a scalar and tensor which are almost degenerate and an axial vector with mass ≈1.6 times the scalar mass.The same procedure applied to the Abelian gauge theory yields unstable results which may indicate the presence of a phase transition.     

On the Variational S-Compactness of Conditional Minimization Problems

For a directedness of conditional optimization problems , we find sufficient conditions for the compactness with respect to the variational S-convergence.     

Synthesis and Analysis of the Sterically Constrained L-Glutamine Analogues (3S,4R)-3,4-Dimethyl-l-glutamine and (3S,4R)-3,4-Dimethyl-l-Pyroglutamic Acid

The nonproteinogenic amino acids (3S,4R)-3,4-Dimethyl-l-pyroglutamic acid and (3S,4R)-3,4-dimethyl-l-glutamine -- found in the cyclic depsipeptides callipeltin B, callipeltin A, and papuamide A -- were synthesized from a common intermediate derived from l-pyroglutamic acid. The diastereoselective introduction of the methyl groups was accomplished by cuprate addition and enolate alkylation, followed by a kinetic epimerization of the C-4 methyl substituent. (3S,4R)-3,4-dimethyl-l-glutamine shows a conformational restriction of its side chain which may be related to its biological function in the natural products where it is found.     

Chiral symmetry breaking in lattice electrodynamics

Chiral symmetry breaking is studied in lattice quantum electrodynamics in the quenched approximation by computer simulation methods. Simulations at zero temperature show that $\text{〈}\text{Ψ}\text{Ψ〉}$ is non-zero for all couplings e² greater than a critical value e_c². The sensitivity of $\text{〈}\text{Ψ}\text{Ψ〉}$ to short-distance features of the lattice action is studied by simulating variant gauge actions. Simulations on asymmetric lattices do not reveal significant temperature dependence in the symmetry breaking dynamics. Subtle effects and limitations of quenched calculations are discussed.