Quotient Groups of Groups of Certain Classes

For an arbitrary variety of groups and an arbitrary class of groups that is closed on quotient groups, we prove that a quotient group G/N of the group G possesses an invariant system with - and -factors (respectively, is a residually -group) if G possesses an invariant system with - and -factors (respectively, is a residually -group) and N (respectively, N is a maximal invariant -subgroup of the group G).     

Standard Enthalpies of Formation of <Emphasis Type="Italic">N</Emphasis>-Methylglycine and Products of Its Dissociation in Aqueous Solutions

Enthalpies of dissolution of crystalline N-methylglycine in water and in aqueous potassium hydroxide solutions are determined at 298.15 K via direct calorimetry. Standard enthalpies of formation of the amino acid and products of its dissociation in aqueous solution are calculated.     

Characteristic features of the nanocrystalline structure formation in Ln2Hf2O7 (Ln = Gd, Dy) compounds

A combination of modern locally sensitive methods of structure analysis based on the interaction of synchrotron radiation with condensed matter was used to study the formation and evolution of crystal structures, change in the size of crystallites, the type and degree of cationic ordering, and features of the local atomic structures of compounds Ln₂Hf₂O₇ (Ln = Gd, Dy) prepared by heat treatment of X-ray amorphous precursors.     

Formation of nanocrystalline structures in the Ln<Subscript>2</Subscript>O<Subscript>3</Subscript>-MO<Subscript>2</Subscript> systems (Ln = Gd,Dy; M = Zr,Hf)

The formation of (Ln³⁺)₂(M⁴⁺)₂O₇ (Ln = Gd, Dy; M = Zr, Hf) nanocrystallites obtained by annealing mixed hydroxides LnM(OH)₇ · nH₂O (precursors) synthesized by coprecipitation has been studied by synchronous thermal analysis, X-ray diffraction (normal and anomalous diffraction of synchrotron radiation), and EXAFS. In the systems under consideration, heat treatment of the X-ray amorphous precursors leads to their dehydration, and at 600–700°C, nanocrystallites with an fcc structure of disordered fluorite start forming. A further increase in temperature is accompanied by crystallite growth (CDD) and considerable change in the local structure of the heat-treated compounds. The crystallization enthalpies and activation energies have been determined.     

Magnetic properties of nanodispersed ferrite powders with cryochemical prehistory

Calcium hexagonal ferrite in the form of a system of nanocrystals has been synthesizes using elements of cryochemical technology for the first time. The obtained ensemble of particles corresponds to the model Stoner-Wohlfarth system according to the following characteristics: the phase composition, the shape of the basic magnetization curve, and the coercive force. The temperature dependences of the magnetization in the range 300–700 K at fixed values of the magnetic field indicate the presence of a transition to the super-paramagnetic (SPM) state. The boundary temperatures T _BH ⁽¹⁾ and T _BH ² of the range of the SPM transition have been determined, and the role of the external magnetic field, which stimulates the transition in this process in accordance with the theory, has been confirmed.     

Two-coordinate position-sensitive monitor-detector of thermal neutrons

Development of new high-flux-intensity neutron sources and the need to equip them with efficient spectrometers raises the problem of designing special-purpose direct-beam monitors-detectors. These detectors feature an extremely low efficiency and a very low attenuation of the incident neutron beam. In this work, a two-coordinate position-sensitive monitor-detector is described that was developed for real-time recording of the profile of neutron beams generated by both steady and pulsed neutron sources. The basic parameters of this device are the following: a coordinate resolution of 4 × 4 mm², a sensitive area of 100 × 100 mm², and a recording efficiency of 10^?6?10^?2. Use of nitrogen as a converter makes it possible to achieve a record low efficiency and still maintain other parameters at a desired level. The device can be combined not only with high-flux-intensity neutron sources already in use worldwide but also with next-generation sources being developed in the United States (SNS) and Japan (JPARC).