On the critical regimes in the theory of randomly forced magnetohydrodynamic turbulence

In this paper large-scale properties of developed magnetohydrodynamic turbulence have been investigated by using double expansion method in the frame of quantum field renormalization group. It has been shown that universal kinetic scaling regime exists, but the double expansion in general leads to qualitatively different results than those provided by the usual -expansion treatment.This work was supported by Slovak Grant Agency for Science.     

Gould-Jacobs reaction of 6-amino-2,3-diphenylquinoxaline

Summary Catalytic hydrogenation of 2,3-diphenyl-6-nitroquinoxaline led to the corresponding amine1 which in turn afforded products3a-i on reaction with alkoxymethylene derivatives2a-i. Thermal cyclization of3b and3f yielded substituted pyrazinoquinolones5b and5f, respectively. Optimal conditions for the successful hydrolysis of ester5b were found. The structures of all products were deduced from their IR, UV,¹H, and¹³C NMR spectroscopic data.Dedicated to Prof.F. Sauter on the occasion of his 65th birthday     

Cross sections of the interactions of He nuclei with protons

⁴He-p collisions at two values of⁴He momenta 8.6 GeV/c and 13.6 GeV/c as well as the³He-p collisions at 13.5 GeV/c have been studies using the one-meter JINR hydrogen bubble chamber. Total, elastic, topological and reaction cross sections have been measured. The cross sections have been determined on a sample of minimum biased events.     

Extraordinary Magnetic Properties of Ca1–xEuxS and Sr1–xEuxS Solid Solutions

The electron paramagnetic resonance (EPR) spectra and the stationary magnetic susceptibility are investigated for Ca_1–x Eu _x S and Sr_1–x Eu _x S solid solutions (0.00005 < x < 0.0032). The EPR spectrum of Eu²⁺ in both matrices contains a wide structureless line in addition to the narrow lines of the superfine structure characteristic of ions with high local symmetry. Because of the extraordinary temperature dependence of this line in CaS:Eu, it is associated with strongly interacting magnetic centers, namely, exchange-coupling pairs and chains or more complex clusters of magnetic ions. At the same time, the dependence of the stationary magnetic susceptibility in the temperature range 4.2–50 K has no peculiarities for CaS:Eu and SrS:Eu and obeys the Curie law.     

Proton-proton and deuteron-deuteron correlations in interactions of relativistic helium nuclei with protons

The reactions⁴Hep pp+X,³Hep pp+X and⁴Hep ddp have been investigated and the correlation function has been measured for protons and deuterons with small relative momenta. Strong positive correlation has been observed for protons related mainly to the final state interactions in¹S₀ state. The root mean square radius of the proton source calculated from the correlation function has been found to be equal to (1.7±0.3) fm and (2.1±0.3) fm for⁴He and³He respectively. It agrees with the known radii of these nuclei.We would like to thank Dr R. Lednicky for discussion, helpful suggestions and for making available the computer program that calculates the theoreticalpp correlation function. The authors also thank Dr D.H. Boal for providing the results of the two-deuteron correlation function calculations.     

Magnetic properties and energy transfer in the luminophors CaS:Eu,Cl

Studies have been performed on the magnetic properties and electron paramagnetic resonance (EPR) spectra of the small-crystal luminophors CaS:Eu,Cl. By comparing the EPR and magnetic susceptibility data we have determined that Eu enters into the CaS matrix primarily in the trivalent state Eu³⁺. We have found that the magnetic susceptibility of the sample with the lowest europium content (5×10⁻³ at. %) has a sharp peak at T≈5 K. A model is proposed of clusters into which the europium ions in these luminophors can associate. On the basis of this model an explanation is given for the anomalous temperature dependence of the magnetic susceptibility as well as a long list of other experimental facts (including peculiarities of the thermal luminescence). Zh. éksp. Teor. Fiz. 113, 1698–1707 (May 1998)     

Penetration of electronic states from silicon substrate into silicon oxide

The depth profiling of O 1s energy loss in silicon oxide near the SiO₂/Si interface was performed using extremely small probing depth. As a result, the energy loss of O 1s photoelectrons with threshold energy of 3.5 eV was found. This value of 3.5 eV is much smaller than the SiO₂ bandgap of 9.0 eV, but quite close to direct interband transition at Γ point in energy band structure of silicon. This can be explained by considering the penetration of electronic states from silicon substrate into silicon oxide up to 0.6 nm from the interface. In addition, the penetrating depth is larger than the thickness of the compositional transition layer.     

Early detection of diseases in plant tissue using spectroscopy – applications and limitations

Plant diseases can greatly affect the total production of food and agricultural materials, which may lead to high amount of losses in terms of quality, quantity and also in economic sense. To reduce the losses due to plant diseases, early diseases detection either based on a visual inspection or laboratory tests are widely employed. However, these techniques are labor-intensive and time consuming. In a view to overcome the shortcoming of these conventional approaches, several researchers have developed non-invasive techniques. Recently, spectroscopy technique has become one of the most available non-invasive methods utilized in detecting plant diseases. However, most of the studies on the application of this novel technology are still in the experimental stages, and are carried out in isolation with no comprehensive information on the most suitable approach. This problem could affect the advancement and commercialization of spectroscopy technology in early plant disease detection. Here, we review the applications and limitations of spectroscopy techniques (visible/infrared, electrical impedance and fluorescence spectroscopy) in early detection of plant disease. Particular emphasis was given to different spectral level, challenges and future outlook.