Present status and prospects for Spin-Echo Small-Angle Neutron Scattering (SESANS) at PIK neutron source

We discuss the present status and the prospects of Spin-Echo Small-Angle Neutron Scattering (SESANS) against the background of the available expertise and the neutron source PIK at PNPI (Gatchina). Two options for SESANS instruments are reviewed: (1) monochromatic with π-flipping permalloy foils and (2) with adiabatic radio frequency spin flippers in a white beam, combined with time-of-flight data collection. A software tool for quantitative prediction of the technical properties of option (2) is developed. For both options, we show that a SESANS instrument which can compete with instruments elsewhere, is realistic. For option (2), we suggest a perspective of spin-echo-length range such that neutron interference experiments become feasible.     

Synthesis of trans-Non-4-EN-2-Ynoic Acid

The synthesis of the title compound has been achieved from 1 -methoxybutenyne in 77% yield in three steps. A reaction mechanism is given to explain exclusive formation of 4,5-trans-configuration.     

Homolytic addition of trichlorobromomethane to styrene

Conclusions The homolytic addition of trichlorobromomethane to styrene, initiated by benzoyl peroxide or by iron pentacarbonyl and a cocatalyst, goes with a rupture of the C-Br and C-Cl bonds in trichlorobromomethane and leads to the formation of three products: 1,1,1-trichloro-3bromo-3-phenylpropane, 1,1,1,3-tetrachloro-3-phenylpropane, and 1,1-dichloro-1,3-dibromo-3phenylpropane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 232–234, January, 1978.     

Electronic structure and spectral characteristics of trinaphthodifuryls

It has been established that in pattern-free hydrated AlPO₄-5 crystals the water molecules are coordinated by more than half of the aluminum-oxygen tetrahedra. The fraction of the tetrahedra with different coordination of the aluminum atoms changes in the order Al_d>Al_t>Al_o, where Al_d is the fraction of the aluminum atoms that coordinate one water molecule, A1_o two water molecules, and Al_t is the fraction of the tetrahedrally coordinated aluminum.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 4, pp. 215–218, July–August, 1994.     

Telomerization of aceylonitkile and methyl acrylate with bromotrichloromethane in the presence of iron pentacarbonyl

Conclusions Initiating systems that contain iron pentacarbonyl and a cocatalyst (iodine, dimethylaniline) make it possible to run the telomerization of acrylonitrile and methyl acrylate with bromotrichloromethane under mild conditions, with a total yield of 55–65% of the first two telomer homologs.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 181–184, January, 1973.     

A Method for Estimating the Entropy of Time Series Using Artificial Neural Networks

Measuring the predictability and complexity of time series using entropy is essential tool designing and controlling a nonlinear system. However, the existing methods have some drawbacks related to the strong dependence of entropy on the parameters of the methods. To overcome these difficulties, this study proposes a new method for estimating the entropy of a time series using the LogNNet neural network model. The LogNNet reservoir matrix is filled with time series elements according to our algorithm. The accuracy of the classification of images from the MNIST-10 database is considered as the entropy measure and denoted by NNetEn. The novelty of entropy calculation is that the time series is involved in mixing the input information in the reservoir. Greater complexity in the time series leads to a higher classification accuracy and higher NNetEn values. We introduce a new time series characteristic called time series learning inertia that determines the learning rate of the neural network. The robustness and efficiency of the method is verified on chaotic, periodic, random, binary, and constant time series. The comparison of NNetEn with other methods of entropy estimation demonstrates that our method is more robust and accurate and can be widely used in practice.     

Effect of high-energy electron beam irradiation on the surface morphology of CaF2/Si(100) heterostructures

The effect of high-energy electron beam irradiation on the surface morphology of CaF₂ films in the course of molecular-beam epitaxy on Si(100) substrates is studied by atomic-force microscopy. It is shown that not only do morphological defects significantly change their shape in the electron beam spot, but also their average height more than doubles.     

Calculation of the output power of a gas laser

A general expression for the gain is analyzed for the limiting case of infinitely many axial modes; the output power is derived as a function of cavity length and pumping. The dispersion width of the Ne 1.15-m line is derived for various He pressures, together with the Weisskopf radius for collision with neutral He atoms.I am indebted to E. V. Voityuk for writing the program and to Yu. V. Troitskii for providing experimental details.