Numerical Characteristics of a Random Variable Related to the Engel Expansions of Real Numbers

Ukrainian Mathematical Journal - It is known that any number x ∈ (0; 1] ≡ Ω has a unique Engel expansion $$ x=sum limits_{n=1}^{infty}frac{1}{left({p}_1(x)+1right)dots...     

Silica-Grafted Tris(neopentyl)aluminum: A Monomeric Aluminum Solid Co-catalyst for Efficient Nickel-Catalyzed Ethene Dimerization

A silica-supported monomeric alkylaluminum co-catalyst was prepared via surface organometallic chemistry by contacting tris(neopentyl)aluminum and partially dehydroxylated silica. This system, fully characterized by solid-state ²⁷Al NMR spectroscopy augmented by computational studies, efficiently activates (ⁿBu₃P)₂NiCl₂ towards dimerization of ethene, demonstrating comparable activity to previously reported dimeric diethylaluminum chloride supported on silica. Three types of aluminum surface species have been identified: monografted tetracoordinated Al species as well as two types of bisgrafted Al species—tetra- and pentacoordinated. Of them, only the monografted Al species is proposed to be able to activate the (ⁿBu₃P)₂NiCl₂ complex and generate the active cationic species.     

Target-ion source unit ionization efficiency measurement by a method of stable ion beam implantation

At the IRIS facility a rather precise method of the target-ion source unit ionization efficiency measurement has been developed. The method exploits an off-line mass-separator for the implantation of the ion beams of selected stable isotopes into a tantalum foil placed inside a Faraday cup in the focal plane of the mass-separator. After the implantation of the required amount of the investigated species, tantalum foil has been inserted into the volume of the target-ion source unit prepared for the on-line utilization at the IRIS on-line separator. The first tests have ensured the ionization efficiency values (90±10)% for Rb and (85±10)% for Cs in the empty combined target-ion source unit, which was used as a reference one. For the target-ion source unit with UC target material inside the measured value of the ionization efficiency of Rb was (52±20)%.     

Transverse energy distributions in Si-nucleus collisions at 10 GeV/nucleon

Transverse energy distributions have been measured for collisions of 10 GeV/nucleon Si with targets of Al, Cu and Pb using a combination of a NaI wall and a uranium based sampling calorimeter. The measured cross sectionsdσ/dE _T anddE _T /dη are consistent with full stopping and an increase, with increasing values ofE _T , of energy flow into large angles.     

Aperiodic behaviour of baroclinic wave packets

The amplitude evolution equation for weakly non-linear wave packets in a continuously stratified and sheared baroclinic flow, in which both dissipation and dispersion effects are strong, is shown to be the generalised time-dependent Ginzburg-Landau equation. This equation possesses both periodic and aperiodic solutions, depending critically on parameter values.     

Time dependent magnetically induced variations in optical transmission of magnetite nanoparticle aqueous suspension

We observe time dependent variations in the light intensity transmitted through an aqueous suspension of Fe₃O₄ nanoparticles caused by applied DC magnetic field. Two types of variations can be distinguished. Fast response takes less than 1ms while slow variations occur at the time interval fromseconds to hundreds of minutes. Possible mechanisms of these variations are discussed. Formation of chain-like structures consisted from iron oxide nanoparticles is responsible for the slow variations. It is also accompanied by a diffraction pattern when the magnetic field is orthogonal to the light beam. Fast variations are due to particle rotation and reorientation of the magnetic moment inside a nanoparticle.     

Recent developments and on-line tests of uranium carbide targets for production of nuclides far from stability

The capacity of uranium carbide target materials of different structure and density for production of neutron-rich and heavy neutron-deficient nuclides have been investigated. The yields of Cs and Fr produced by a 1 GeV proton beam of the PNPI synchrocyclotron and release properties of different targets have been measured. Yields and release efficiencies of Cs and Fr produced from a high density UC target material and from low density UCx prepared by the ISOLDE method at IRIS in the collaboration with PARRNe group from Orsay are compared. The yields from ISOLDE original target are presented for comparison as well.     

X-ray diffraction study of zirconia pillared clays

X-ray powder diffraction (XRPD) and X-ray radial electronic distribution density (RED) of initial and zirconia-pillared interlayered clays (Zr-PILC) were studied. After pillaring, the basal (001) spacing was found to increase from 11 Å in the initial clay kept under air to 17.7 Å in Zr-PILC. The structure of zirconium nanopillars was characterized. The interatomic distances with corresponding coordination numbers obtained from the RED curves were close to those in zirconium tetramers.This revised version was published online in December 2005 with corrections to the Cover Date.     

Local structure of pseudoboehmites

Summary The structure of pseudoboehmite was studied by the method of wide-angle X-ray scattering (WAXS). The samples of pseudoboehmite with various characteristics produced by different methods were examined in order to obtain the most complete information about their structure. In contrast to reference data, it was found that modifications in the structure of pseudoboehmite layers occur viathe insertion of additional water molecules.     

Characteristics of low-temperature luminescence of cadmium tungstate single crystal-luminescence

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 56, No. 2, pp. 246–251, February, 1992.