Second experiment at VASSILISSA separator on the synthesis of the element 112

The upgraded separator VASSILISSA was used to confirm results of previous experiments on the synthesis of the heavy isotopes of the element 112 obtained in complete-fusion reactions of ⁴⁸Ca and ²³⁸U. An additional reason was the non-observation of any events in the same reaction studied with the BGS separator at Berkeley. Limits of for the atomic mass number of the observed spontaneously fissioning isotope were measured. The obtained results on the decay mode, half-life and production cross-section are in agreement with those obtained in our first experiment.Received: 10 June 2003, Revised: 29 July 2003, Published online: 2 December 2003PACS: 23.60. + e decay - 25.70.-z Low and intermediate energy heavy-ion reactions - 25.85.Ca Spontaneous fission - 27.90. + b      

Superheavy hydrogen (5)H

Experimental search for (5)H using a secondary beam of (6)He has been performed. The transfer reaction (1)H((6)He,(2)He)(5)H was studied by detecting two protons emitted from the decay of (2)He. A peak consistent with a (5)H resonance at 1.7+/-0.3 MeV above the n+n+t threshold was observed, with a width of 1.9+/-0.4 MeV. The angular distribution of the (1)H((6)He,(2)He)(5)H reaction was measured as well as the energy correlation of the two protons.     

Stability of liquid-metal ion sources

In this paper we find the parameters (radii, lengths, velocities) of the jets produced in liquid-metal ion sources. The jet stability with respect to developing sausages (Rayleigh instability) is studied. The Rayleight instability is shown to occur for rather large currents (in long jets). The currents critical for the instability initiation are calculated for Ga and Au sources. The results are in accordance with the experimental data available. In the case of Ga, the accordance is achieved only for the hot jet model (TT _m , whereT _m is the melting temperature), when the viscosity is appreciably lower.     

Photoluminescence and EPR of porous silicon formed on <Emphasis Type="Italic">n</Emphasis><Superscript>+</Superscript> and <Emphasis Type="Italic">p</Emphasis><Superscript>+</Superscript> single crystals implanted with boron and phosphorus ions

The effect of combined doping by shallow donor and acceptor impurities on boosting the quantum yield of porous-silicon photoluminescence (PL) in the visible and near IR range was studied using phosphorus and boron ion implantation. Nonuniform doping of samples and subsequent oxidizing annealing were performed before and after porous silicon was formed on silicon single crystals strongly doped by arsenic or boron up to ≈10¹⁹ cm^?3. The concentration of known P_b centers of nonradiative recombination was controlled by electron paramagnetic resonance. It is shown that there is an optimal joined content of shallow donors and acceptors that provides a maximum PL intensity in the vicinity of the red part of the visible spectrum. According to estimates, the PL quantum yield in the transitional n ⁺⁺-p ⁺ or p ⁺⁺-n ⁺ layer of porous silicon increases by two orders of magnitude as compared to that in porous silicon formed on silicon not subjected to ion irradiation.     

A dynamic ion cooling technique for FTICR mass spectrometry

A fast dynamic ion cooling technique based upon the adiabatic invariant phenomenon for Fourier transform ion cyclotron resonance mass spectrometry (FTICR) is presented. The method cools ions in the FTICR trap more efficiently, within a few hundred milliseconds without the use of a buffer gas, and results in a substantial signal enhancement. All performance aspects of the FTICR spectrum, e.g., peak intensities, mass resolution, and mass accuracy, improve significantly compared with cooling based on ion-ion interactions. The method may be useful in biological applications of FTICR, such as in proteomic studies involving extended on-line liquid chromatography (LC) separations, in which both the duty cycle and mass accuracy are crucially important.     

Synthesis of multicentered polyimide initiators for the preparation of regular graft copolymers via controlled radical polymerization

Multicentered initiators for the controlled (pseudoliving) radical polymerization are synthesized via polymer analog transformation of hydroxyl-containing polyimides based on o-aminophenols. Conditions providing variations in the degree of functionalization of polyimides by initiating 2-bromoisobutyrate groups are determined, and optimum conditions for the preparation of macroinitators containing the above groups in each repeat polyimide unit are found. Via the method of controlled radical polymerization with the atom transfer on multicentered macroinitiators in the presence of complexes of univalent copper halides, graft copolymers of poly(methylmethacrylate) on polyimide backbone are obtained. Molecular-mass characteristics of graft copolymers are studied via multiple-detection size-exclusion liquid chromatography. Preparation of graft copolymers (polymer brushes) with a homogeneous grafting density and a homogeneous length of side chains necessitates grafting of the side chain on the polyimide initiator, which contains initiating groups in each repeat unit.     

Exposure of nuclear track emulsion to 8He nuclei at the ACCULINNA separator

Nuclear track emulsion is exposed to a beam of radioactive ⁸He nuclei with an energy of 60 MeV and enrichment of about 80% at the ACCULINNA separator. Measurements of 278 decays of the ⁸He nuclei stopped in the emulsion allow the potential of the α spectrometry to be estimated and the thermal drift of ⁸He atoms in matter to be observed for the first time.     

Determination of bis(2-ethylhexyl) phthalate in water by high-performance liquid chromatography with direct on-column preconcentration

A technique for the direct preconcentration of bis(2-ethylhexyl) phthalate (DEHP) on a reversedphase analytical column was proposed for the analysis of water samples by high-performance liquid chromatography (HPLC). A procedure for determining DEHP in surface-water and atmospheric precipitations in the laboratory and in the field was developed (the limit of detection is 0.1 Μg/L, the limit of determination is 0.3 Μg/L, and the relative standard deviation is 20 or 6% at a DEHP concentration of 0.3 or 10 Μg/L, respectively). The concentration levels of DEHP as a chemical tracer for the transfer and migration of air and water masses were examined in Lake Baikal water and in the snow cover of the Baikal region.     

N-terminal tagging strategy for De Novo sequencing of short peptides by ESI-MS/MS and MALDI-MS/MS

The major portion of skin secretory peptidome of the European Tree frog Hyla arborea consists of short peptides from tryptophyllin family. It is known that b-ions of these peptides undergo head-to-tail cyclization, forming a ring that can open, resulting in several linear forms. As a result, the spectrum contains multiple ion series, thus complicating de novo sequencing. This was observed in the Q-TOF spectrum of one of the tryptophyllins isolated from Hyla arborea; the sequence FLPFFP-NH₂ was established by Edman degradation and counter-synthesis. Though no rearrangements were observed in FTICR-MS and MALDI-TOF/TOF spectra, both of them were not suitable for mass-spectrometry sequencing due to the low sequence coverage. To obtain full amino acid sequence by mass spectrometry, three chemical modifications to N-terminal amino moiety were applied. They include acetylation and sulfobenzoylation of N-amino group and its transformation to 2,4,6-trimethylpyridinium by interaction with 2,4,6-trimethylpyrillium tetrafluoroborate. All three reagents block scrambling and provide spectra better than the intact peptide. Unfortunately, all of them also readily react with lysine side chain. Hence, all investigated procedures can be used to improve sequencing of short peptides, while acetylation is the recommended one. It shows excellent results, and it is plain and simple to perform. This is the procedure of choice for MS-sequencing of short peptides by manual or automatic algorithms.     

Magnetic Properties of Ti3O5 with Chromium Additions

Magnetic susceptibility measurements were used to study solid solutions Ti_3?xCr_xO₅ (0 ? × ? 0.17). Contributions to magnetic susceptibility for the α-phase were defined by the statistical analysis of the experimental data. A conclusion was made on the varing character of exchange interactions in α-Ti_3?xCr_xO₅ with increasing Cr content. In the present work, the information given indicates that Cr stabilizes the high-temperature α-Ti₃O₅ and decreases the temperature of semiconductor-metal phase transition. Magnetic properties of low-temperature α-Ti₃O₅ phase with chromium addition are shown to be explained by the existence of exchange-coupled pairs Ti³⁺? Cr³⁺.