Gas-phase deprotonation of arylalkylamines. A collision-induced dissociation study

The collision-induced dissociation (CID) of deprotonated arylalkylamines of general formula R(1)C(6)H(4)CHR(2)CH(2)NR(3)(2) (where R(1) = H, OH, F or NO(2); R(2) = H or OH; R(3) = H or CH(3)) generated by negative chemical ionization with H(2)O and D(2)O as ionizing reagents, is discussed. The negative chemical ionization mass spectra show that, in the absence of a hydroxy group in the aromatic ring, deprotonation takes place at the benzylic position whereas the proton is lost from the OH group when present. The nitro compound forms only M(-.) ions. The CID spectra of the deprotonated molecules show that fragmentations are strongly dependent on the structural features of the molecules, namely the presence or absence of substituents in the aromatic ring or aliphatic chain. Copyright 1999 John Wiley & Sons, Ltd.     

The surface morphology of pyrolytic graphite irradiated by hydrogen atoms

Interaction between atomic hydrogen and pyrolytic graphite is investigated by thermal desorption spectroscopy, atomic force microscopy, and scanning tunneling microscopy. After exposure in an atomic hydrogen flow, the initially smooth graphite surface becomes rough, with a height difference of several nanometers. When heated, the samples release hydrogen and their surface is smoothed out, showing monolayer-deep etch pits. After multiple sorption-desorption cycles, both the linear sizes and the depth of the pits increase.     

Hydrogen and helium in nickel and 12Kh18N10T steel

A brief review of data for the influence of helium on the hydrogen sorption and mechanical properties of nickel and 12Kh18N10T steel is presented. When in the metallic matrix, helium considerably deteriorates the ductility of these metals. It is shown that ³He present in 12Kh18N10T steel generates high-energy hydrogen traps.     

Conditions for the development of free radicals as a result of friction between polymers,studied by the electron-paramagnetic-resonance method

An apparatus and a method for the direct recording of stable free radicals arising as a result of frictions between polymers are described; the method is based on electron paramagnetic (spin) resonance (ESR). It is shown that the for mation of free radicals depends on the combinations of external loading conditions.

     

Muon diagnostics of the Earth’s atmosphere and magnetosphere

A method of distant monitoring of the Earth’s magnetosphere and atmosphere is described, which is based on the close correlation between the modulations in the flux of atmospheric muons detected at the Earth’s surface and the dynamic processes in the Earth’s magnetosphere and atmosphere and implies the use of large-area muon hodoscopes with high angular accuracy of muon detection. The results of the analysis of the experimental data obtained on the muon hodoscopes used at the Moscow Engineering Physics Institute show that muon detection at the Earth’s surface in the hodoscopic mode gives a qualitatively new information about the main sources of muon flux modulation.     

Astrophysical S-factors from asymptotic normalization coefficients

S-factors for direct capture reactions can be found at astrophysical energies from asymptotic normalization coefficients which provide the normalization of the tail of the overlap function. For example the overlap for ⁸B → ⁷Be+p defines the S-factor for ⁷Be (p, γ)⁸B. Peripheral transfer reactions offer a technique to determine these asymptotic normalization coefficients. As a test of the technique, the ¹⁶O(³He, d)¹⁷F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of ¹⁷F. The S-factors for ¹⁶O(p, γ)¹⁷F calculated from these ¹⁷F → ¹⁶O+p asymptotic normalization coefficients are found to be in very good agreement with recent measurements. Following the same technique, the ¹⁰B(⁷Be, ⁸B)⁹Be and ¹⁴N(⁷Be, ⁸B)¹³C reactions have been used to measure the asymptotic normalization coefficient for ⁷Be(p, γ)⁸B. This result provides an indirect determination of S ₁₇(0).     

Isolation of NO(3)(-)-N as 1-phenylazo-2-naphthol (Sudan-1) for measurement of delta(15)N

The conversion of nitrate (NO(3)(-)) to 1-phenylazo-2-naphthol (Sudan-1) has been examined as a method for natural abundance measurement of delta(15)N of NO(3)(-). The reaction results in dilution of NO(3)(-)-N with only one reagent-derived N and the product is readily concentrated from dilute samples by reverse phase chromatography. There is systematic isotopic fractionation during the reaction, but this can be allowed for by analysing known NO(3)(-) standards along with each sample set. Sudan-1 prepared from surface water samples containing approximately 50 &mgr;g NO(3)(-)-N can be analysed by automated continuous flow isotope ratio mass spectrometry with a precision of 0.2 per thousand (one standard deviation) and the accuracy is not affected by interference from other nitrogenous species in the sample or reagents. Copyright 1999 John Wiley & Sons, Ltd.     

Principle of maximal randomness and parity violation in turbulence

We show that in the self-consistent equations for equal-time correlation functions of velocity fluctuations obtained in the model of developed turbulence based on the maximal randomness principle, infrared divergences are absent from all orders of the perturbation theory. We analyze the additional ultraviolet (UV) divergences that appear in the two-loop approximation of the self-consistent equations. We show that in the system with conserved parity, these divergences can be eliminated using the existing ambiguity in the solution. In the case of parity violation in the system, the UV divergences have a logarithmic form, which can indicate a deviation from the Kolmogorov scaling.     

Evaluated benchmark experiments at critical assemblies simulating features of an HTHR at the ASTRA facility

The design of the ASTRA facility and critical assemblies that simulate physics features of modular high-temperature reactors (HTHR-Ms) with a graphite moderator and reflectors loaded with fuel particles having multilayer ceramic coatings is described in detail. Geometrical dimensions of the main elements and regions of the critical assemblies, composition of the materials used, and experimental results for various configurations of the critical assemblies are presented. A detailed computational benchmark model allowing for the structural and compositional features of the critical assembly configurations in question is developed on the basis of all the above data. The results are to be used for verification of the neutronics codes used for calculations of high-temperature helium-cooled reactors.