Towards high precision in-trap laser spectroscopy of highly charged ions

The extremely strong fields that exist around the nuclei of few-electron heavy ions drastically change the properties of the electronic system such as energy level spacings, lifetimes and magnetic moments. In turn, the electrons serve as sensitive probes for nuclear properties such as size, magnetic moment and spatial distribution of charge and magnetization. The energies of their forbidden fine and hyperfine structure transitions strongly depend on the nuclear charge and shift from microwave domains in or close to the optical domain. Thus, they become accessible for laser spectroscopy and its potentially high precision. A number of such measurements have been performed in storage rings and electron beam ion traps, and have yielded results with relative accuracies in the permille region. We present here an experiment under development at GSI Darmstadt which aims to significantly increase the accuracy by employing charged particle traps which allow to slow the ion motion nearly to rest, thus reducing Doppler effects and increasing the possible accuracy to the more than ppm region.     

A Rapid and Facile Synthesis of Nanofibrillar Polyaniline Using Microwave Radiation

We present the first fast and facile microwave assisted synthesis of polyaniline (PANI) nanofibers (“MWA synthesis”). Under conventional synthesis (CS), the polymer was produced with 79.7% yield after 5 h at ambient temperature. However, under microwave irradiation, the nanofibers were produced with yield of 76.2% after only 5 min, i.e., with 78.8% after 20 min at ambient temperature. The FTIR and Raman spectra show the PANI structure in all samples either synthesized conventionally or in the microwave. SEM and TEM confirm the nanofibrillar morphology.

     

On capability of finite abelian groups

Baer characterized capable finite abelian groups (a group is capable if it is isomorphic to the group of inner automorphisms of some group) by a condition on the size of the factors in the invariant factor decomposition (the group must be noncyclic and the top two invariant factors must be equal). We provide a different characterization, given in terms of a condition on the lattice of subgroups. Namely, a finite abelian group G is capable if and only if there exists a family {H _i } of subgroups of G with trivial intersection, such that the union generates G and all quotients G/H _i have the same exponent. Other variations of this condition are also provided (for instance, the condition that the union generates G can be replaced by the condition that it is equal to G). The work presented here is partially supported by NSF/DMS-0805932.     

Quantized vortices in the ideal bose gas: a physical realization of random polynomials

We propose a physical system allowing one to experimentally observe the distribution of the complex zeros of a random polynomial. We consider a degenerate, rotating, quasi-ideal atomic Bose gas prepared in the lowest Landau level. Thermal fluctuations provide the randomness of the bosonic field and of the locations of the vortex cores. These vortices can be mapped to zeros of random polynomials, and observed in the density profile of the gas.     

Path integrals for quadratic lagrangians on <Emphasis Type="Italic">p</Emphasis>-adic and adelic spaces

Feynman’s path integrals in ordinary, p-adic and adelic quantum mechanics are considered. The corresponding probability amplitudes K(x″, t″; x′, t′) for two-dimensional systems with quadratic Lagrangians are evaluated analytically and obtained expressions are generalized to any finite-dimensional spaces. These general formulas are presented in the form which is invariant under interchange of the number fields ℝ ↔ ℚ _p and ℚ ↔ ℚ _p , p ≠ p′. According to this invariance we have that adelic path integral is a fundamental object in mathematical physics of quantum phenomena.     

Crosslinking of an unsaturated polyester resin in the mould: Modelling and heat transfer studies

The crosslinking of unsaturated polyester was studied by using an experiment and a mathematical model of the process. Temperature–time profiles were recorded in the centre of the sample inside the mould at the outer wall of the cylindrical copper mould, and in the bulk of the heated air bath. A numerical model was constructed by taking into account the heat transferred by convection from the air to the mould surface and the heat transferred by conduction through the resin, as well as the heat generated by the crosslinking reaction. The convection heat transfer coefficient was determined in independent experiments with the empty copper mould. Introduction of the carbon base filler reduced the amount of heat generated in the composite due to the less reactive component in the composite. As a result, it lowered the temperature of the resin. By recording the temperature-time and the degree of crosslinking time profiles developed within the sample extensive knowledge of the process can be obtained. The effects of the convection heat transfer on the rate of mould heating, and the conduction heat transfer through the mould as well as the internal heat generated by the crosslinking reaction are visibly shown, despite a complexity of the process.     

SmartMetals: a new method for metal identification based on fuzzy logic

This paper presents a method of searching, identifying and cross‐referencing metal alloys based on their chemical composition and/or mechanical properties, typically obtained by analysis and tests. The method uses a general pattern similar to the approach of a human expert, and relies on a classification of metals based on metallurgical expertise and fuzzy logic for identifying metals and comparing their chemical and mechanical properties. The algorithm has been tested and deployed in real applications for fast metal identification and finding of unknown equivalents, by the leading companies in the field. The same principles can also be used in other domains for similar problems, such as organic and inorganic materials identification and generic drugs comparison. Copyright © 2009 John Wiley & Sons, Ltd.     

Co-crystallization of octahedral and icosahedral fluoroanions in K3(AsF6)(B12F12) and Cs3(AsF6)(B12F12). Rare examples of salts containing fluoroanions with different shapes and charges

Crystals grown from anhydrous HF solutions of CsAsF₆ and Cs₂B₁₂F₁₂ or KAsF₆ and Cs₂B₁₂F₁₂ are shown by Raman spectroscopy and single-crystal X-ray diffraction to be the ternary salts K₃(AsF₆)(B₁₂F₁₂) or Cs₃(AsF₆)(B₁₂F₁₂). Both compounds exhibit a modified version of the anti-perovskite structure. They are rare examples of crystals that simultaneously contain octahedral and icosahedral molecular species and are also rare examples of salts containing fluoroanions with different shapes and charges. The crystallographic results show that both compounds are densely packed.     

New manganese-scaffolded organic triple-deckers based on quinoxaline, pyrazine and pyrimidine cores

The thermolytic coupling of Ph(2)CN(2) and (t-Bu)(Ph)CN(2) with doubly cyclomanganated 2,5-diphenylpyrazine and 4,6-diphenylpyrimidine afforded substantial amounts of new triple decker compounds of either C(i) and C(2) symmetry respectively containing, in both series, two eta(3)-bonded Mn(CO)(3) fragments which intervene as scaffolds sustaining the helical non-conjugated triaryl backbone. The molecular structures of two pyrazine derivatives show a typical non-parallel stacking of the aromatic rings and the encapsulation of the central pyrazyl fragment with interplanar centroid-to-centroid distances of ca. 3.5 A. The stacking of the aromatics in the triple-decker pyrimidine derivatives has been assessed by (1)H NMR experiments at low temperature. All the triple-decker-type compounds are electroactive. Pyrimidine triple-deckers can reversibly be electrochemically reduced to the corresponding anions.     

Nuclear excitation by positron annihilation with bound electrons in a screened atomic potential

We have calculated the total cross section for the process of nuclear excitation in positron-bound electron annihilation. The calculations presented in this work use a spherically symmetric screened atomic potential. Comparisons with more approximate treatments of the process are made.