The behavior of radioactive metals (Am, Eu, Sr) during the processing of radioactive graphite in salt melts

The behavior of Am, Eu, Sr radionuclides was investigated by thermodynamic modeling method at heating of radioactive graphite in NaCl - KCl - Na2CO3 - K2CO3 molten salt with additives of nickel oxide NiO. The integrated thermodynamic analysis was carried out by means of TERRA software in temperature range 373-3273 K to determine possible composition of condensed and gaseous phases. It was established that americium is in gaseous state in temperature range 2773-3273 K. Europium is in the forms of gaseous EuO and Eu in temperature range 2373-3273 K. Strontium is in the forms of gaseous SrCl2, SrCl, Sr, SrO in temperature range 2373-3273 K. © Published under licence by IOP Publishing Ltd

Rotational covariance and light-front current matrix elements

Light-front current matrix elements for elastic scattering from hadrons with spin~1 or greater must satisfy a nontrivial constraint associated with the requirement of rotational covariance for the current operator. Using a model $\rho$ meson as a prototype for hadronic quark models, this constraint and its implications are studied at both low and high momentum transfers. In the kinematic region appropriate for asymptotic QCD, helicity rules, together with the rotational covariance condition, yield an additional relation between the light-front current matrix elements.Comment: 16 pages, [no number

Weak Decays in the light--front Quark Model

We study the form factors of heavy--to--heavy and heavy--to--light weak decays using the light--front relativistic quark model. For the heavy--to--heavy B \ra D^{(\ast)} semileptonic decays we calculate the corresponding Isgur--Wise function for the whole kinematic region. For the heavy--to--light B\ra P and B\ra V semileptonic decays we calculate the form factors at $q^2 = 0$; in particular, we have derived the dependence of the form factors on the $b$--quark mass in the m_b \ra \infty limit. This dependence can not be produced by extrapolating the scaling behavior of the form factors at $q^2_{max}$ using the single--pole assumption. This shows that the $q^2$ dependence of the form factors in regions far away from the zero--recoil could be much more complicated than that predicted by the single--pole assumption.Comment: 24 pages, Latex, Postscript figure included at the en

Deuteron Magnetic and Quadrupole Moments with a Poincar\'e Covariant Current Operator in the Front-Form Dynamics

The deuteron magnetic and quadrupole moments are unambiguosly determined within the front-form Hamiltonian dynamics, by using a new current operator which fulfills Poincar\'e, parity and time reversal covariance, together with hermiticity and the continuity equation. For both quantities the usual disagreement between theoretical and experimental results is largely removed.Comment: To appear in Phys. Rev. Let

Deep inelastic scattering and final state interaction in an exactly solvable relativistic model

In the theory of deep inelastic scattering (DIS) the final state interaction (FSI) between the struck quark and the remnants of the target is usually assumed to be negligible in the Bjorken limit. This assumption, still awaiting a full validation within nonperturbative QCD, is investigated in a model composed by two relativistic particles, interacting via a relativistic harmonic oscillator potential, within light-cone hamiltonian dynamics. An electromagnetic current operator whose matrix elements behave properly under Poincar\'e transformations is adopted. It is shown that: i) the parton model is recovered, once the standard parton model assumptions are adopted; and ii) when relativistic, interacting eigenfunctions are exactly taken into account for both the initial and final states, the values of the structure functions, averaged over small, but finite intervals of the Bjorken variable $x$, coincide with the results of the parton model in the Bjorken limit.Comment: 26 pages, to appear in Phys. Rev. C (May 1998

СИСТЕМА СТАНДАРТНЫХ ОБРАЗЦОВ НАУЧНОГО МЕТОДИЧЕСКОГО ЦЕНТРА ГОСУДАРСТВЕННОЙ СЛУЖБЫ СТАНДАРТНЫХ ОБРАЗЦОВ СОСТАВА И СВОЙСТВ ВЕЩЕСТВ И МАТЕРИАЛОВ ФГУП «УНИИМ»

Since 1960s UNIIM performs research in the field of needs in reference materials of composition and properties of substances and materials (RM) as well as develops it. During the research UNIIM has developed 757 types of RMs for metrological measurement assurance of factors of composition and properties of substance and materials for test laboratories of chemical, pharmaceutical, fuel, food industry, agriculture, metallurgy and ecological monitoring laboratories. List ofRMs enlarges thanks to development of UNIIM standards and transmission measurement facility from State standards of units. Taking into account the actual requirements in the field of measurements, the UNIIM's key destination is to assure the accuracy and the metrological traceability of measurements. The present-day system of RMs to be developed in UNIIM includes RMs of composition of inorganic and organic compounds and their solutions, fuels, stable isotopic materials, water, grounds, food products, biomaterials, nanomaterials, metals, alloys and other materials offerrous and non-ferrous industry, RMs of properties (thermodynamic, magnetic, physical-chemical, technical) of substances and materials. The present article considers history of RMs list development which were created by UNIIM and the strategy of this direction.Исследования в области мониторинга потребности в стандартных образцах состава и свойств веществ и материалов (СО), создание стандартных образцов УНИИМ проводит c 60-х годов ХХ века. За годы исследований УНИИМ разработал 757 типов СО для метрологического обеспечения измерений показателей состава и свойств веществ и материалов, предназначенных для испытательных лабораторий химической, фармацевтической, топливной, пищевой промышленности, сельского хозяйства, металлургии, лабораторий экологического мониторинга. Развитие номенклатуры СО, выпускаемых УНИИМ, неразрывно связано с развитием эталонной базы УНИИМ и формированием средств передачи измерительной возможности от государственных эталонов единиц величин. Учитывая современные требования в области измерений, ключевым предназначением СО УНИИМ является обеспечение точности и метрологической прослежи-ваемости измерений. Современная система СО, разрабатываемых и выпускаемых УНИИМ, включает СО состава неорганических и органических соединений и их растворов, топлив, стабильных изотопных материалов, воды, почвы, пищевых продуктов, биологических материалов, наноматериалов, металлов, сплавов и других материалов цветной, черной металлургии, СО свойств (термодинамических, магнитных, физико-химических, технических) веществ и материалов. Настоящая статья посвящена историческим этапам развития номенклатуры СО, разрабатываемых и выпускаемых УНИИМ, а также перспективам развития в этом направлении