Electromagnetic dissociation of relativistic 8B nuclei in nuclear track emulsion

Experimental data on fragmentation channels in peripheral interactions of ⁸B nuclei in nuclear track emulsions are presented. A detailed analysis made it possible to justify selections of events of the electromagnetic-dissociation process ⁸B → ⁷Be + p and to estimate its cross section. Events of ¹⁰C peripheral dissociation that were observed in the same exposure are described.     

Symmetry analysis and exact solutions of one class of (1?+?3)-dimensional boundary-value problems of the Stefan type

We present the group classification of one class of (1 + 3)-dimensional nonlinear boundary-value problems of the Stefan type that simulate the processes of melting and evaporation of metals. The results obtained are used for the construction of the exact solution of one boundary-value problem from the class under study.     

Synthesis,Self-Association,and Solubilizing Ability of an Amphiphilic Derivative of Poly(ethylene glycol) Methyl Ether

A new amphiphilic derivative–methoxy(polyethoxy)ethyl stearate has been synthesized with the goal of creating therefrom systems for delivery and enhancement of bioavailability of piperine. The aggregation and solubilizing properties of ω-methylpoly(oxyethylene) stearate have been studied by means of a set of physicochemical methods.     

Source of polarised deuterons

The proposed project assumes the development of a universal high-intensity source of polarized deuterons (protons) using a charge-exchange plasma ionizer. The design output current of the source will be up to 10mA for ↑ D⁺(↑ H⁺) and polarization will be up to 90% of the maximal vector (±1) and tensor (+1,−2) polarization. The project is based on the equipment which was supplied within the framework of an agreement between JINR and IUCF (Bloomington, USA). The project will be realized in close cooperation with INR (Moscow, Russia). The source will be installed in the linac hall (LU-20) and polarization of beams will be measured at the output of LU-20. The main purpose of the project is to increase the intensity of the accelerated polarized beams at the JINR Accelerator Complex up to 10¹⁰ d/pulse. Calculations and first accelerator runs have shown that the depolarization resonances are absent for the deuteron beam in the entire energy range of the NUCLOTRON. The source could be transformed into a source of polarized negative ions if necessary. The period of reliable operation without participation of the personnel should be within 1000 hours. The project should be implemented within two to two and a half years from the start of funding.     

Tuning rate of the bergman cyclization of benzannelated enediynes with ortho substituents

[reaction: see text] The Bergman cyclization of benzannelated enediynes is highly sensitive to ortho substitution. This finding opens possibilities for the rational design of conformer-specific and pH-dependent DNA-cleaving agents.     

Electron Diffraction Analysis of the Fracture Zone of Fe–0.45C–17Mn–3Al Steel Subjected to Multicyclic Fatigue Tests

The methods of transmission electron microscopy are used to investigate the structure and phase content of Fe–0.45C–17Mn–3Al steel subjected to multicyclic fatigue tests to failure after intermediate electrostimulation. It is demonstrated that electrostimulation does not change the mechanism of steel failure. An increase in the operating life time of samples after electrostimulation in the intermediate test stage is connected with the hindered -martensitic transformation, the relaxation of stress concentrators, and the reduction of the volume fraction of the critical dislocation (network) substructure in which -martensite is mainly developed.     

Simulation of the Processes of Irreversible Aggregation in the Systems of Molecular Chains with Different Distribution of Associating Groups

The processes of the irreversible aggregation of chain molecules with various numbers of associating groups are studied by the Monte Carlo method using the Eden model. Three-dimensional lattice systems are considered. The model developed qualitatively reproduces the main structural (morphological) characteristics that are observed experimentally for the aggregates composed of macromolecules of ionic polymers under the conditions of strong segregation. It is established that the chains with one associating terminal group form tree-like coral-shaped aggregates; associating groups form the skeleton with a large number of branches at the periphery. It is shown that the chains with the number n _s 2 of associating groups form aggregates whose structures correspond to a three-dimensional network. Integral characteristics of a system are scale-invariant; molecular parameters, such as the chain length N and the number of associating groups n _s, enter into corresponding scaling dependences in the form of scaling multipliers N and n _s . Critical indices and , as well as main index determining the dependence of the mean aggregate sizes on the number n of constituting molecules, are estimated. It is established that an increase in the number of associating groups in a chain results in the formation of more compact aggregates with smaller characteristic size of a network cell. For the model considered, such an effective compression is explained by the intensification of branching, i.e., by the dispersal of growth points, rather than by the folding of chains (on the contrary, their substantial fraction is attached to the cluster in greatly extended conformations). The important role of intra- and interchain screening effects arising during the formation of local morphology of aggregates is demonstrated. As a result of such screening, the sizes of lattice nodes composed of associating groups seem to be the nonmonotonic function of the number of these groups in the chain.     

Electronic absorption spectra or carbonium and dicarbonium ions containing heterocyclic rings with a biphenylene base

An analysis has been made of -^* -electronic excitations of carbonium and dicarbonium ions obtained by the interaction of concentrated sulfuric or fluoboric acid with alcohols or glycols containing a heterocyclic bridge structure, i.e., nuclei of dibenzofuran, dibenzothiophene, carbazole, and N-methylcarbazole; this analysis has been aimed at establishing a correlation of their structure and spectral characteristics. From an analysis of experimental data, calculated results, and indexes quantitatively characterizing the structure of the -^* -electronic excitations, it has been established that there are four electronic transitions in the visible region of the electronic absorption spectrum of the carbonium ions. The long-wave, intense band of the spectrum is due to superposition of intense (p-type) and weak (-type) transitions proceeding from corresponding excitations of the heterocyclic fragment. In the electronic spectra of the dicarbonium ions, a doublet of p-transitions is clearly manifested. It has been shown that the interaction of chromophores through the bridge structure increases by a factor of approximately 1.8 when the change is made from dibenzofuran to dibenzothiophene, carbazole, and Nmethylcarbazole; in comparison with the corresponding dihydroxycarbonium ions, the degree of interaction of the chromophores is greater by a factor of approximately 1.5.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 3, pp. 284–291, May–June, 1990.