Formation of Novel Dinuclear Mixed-Valence Rhodium Complexes by Intramolecular Migration of a Chelating Ligand

Significantly different coordination spheres are displayed by the two central atoms of 2 , the first representative of a novel type of mixed-valence dinuclear Rh⁰–Rh^II compound, which was synthesized from the stibane-bridged complex 1 . The Rh−Rh distance determined by an X-ray crystal structure analysis of 2 indicates a metal–metal interaction between the two metal centers.     

5,5′-Diuracilyl Species from Uracil and [AuCl4]−: Nucleobase Dimerization Brought about by a Metal

Not only UV radiation can bring about the dimerization of the pyrimidine nucleobase uracil, a metal ion can as well! The reaction proceeds by a reductive elimination process of two cis-oriented uracil entities, each bonded to Au^III through C5 [Eq. (a)]. R/R′=H/CH₃, CH₃/CH₃, H,C₅H₉O₄     

Synthesis and solution properties of rodlike polyelectrolytes

The synthesis and the solution behavior of rigid, rodlike cationic polyelectrolytes having (i) poly(p-phenylene) backbones and (ii) main chains composed of 4,4“-bis(2,2′:6′,2”-terpyridine)2′,5′-dihexyl-p-terphenyl moieties and ruthenium(II) centers are presented. All these polymers are shown to have a homogeneous constitution and degrees of polymerization of up to P_n ≈ 70. Their solution properties were analyzed using viscosimetry, small-angle X-ray scattering (SAXS) and osmometry. Pronounced polyelectrolyte effects were found in salt-free solutions using viscosimetry. Small-angle X-ray scattering demonstrated directly the strong correlation of the counterions and the macroions. The osmotic coefficients measured in salt-free solution as function of polyelectrolyte concentration were found to be lower than predicted by the cell model.     

Isolation and Characterization of Wax Esters in Fennel and Caraway Seed Oils by SPE-GC

A rapid method for the isolation and quantitative determination of wax esters in vegetable oils was developed. For the first time wax esters in oils were separated from the triglyceride matrix by means of solid-phase extraction, which allows rapid sample preparation in parallel and therefore a high sample throughput. The thus obtained wax ester fractions of fennel and caraway seed oils were analyzed by high temperature gas chromatography. GC-MS analyses were carried out using electron impact ionization in order to characterize the wax ester fraction. With respect to the results of the GC-MS analyses different isomers of saturated wax esters with the same carbon number were observed. Additional monounsaturated wax esters with an unsaturated fatty acid moiety were identified.     

Novel antimitotic agents related to tubuloclustin: synthesis and biological evaluation

Tubuloclustin [N-(7-adamant-2-yloxy-7-oxoheptanoyl)-N-deacetylcolchicine], a highly cytotoxic anti-tubulin compound is known for its ability to promote microtubule disassembly followed by the formation of tubulin clusters of unique morphology. Three series of antimitotic agents related to tubuloclustin were designed and synthesized in order to enhance the molecular diversity of “tubuloclustin-like” family of compounds. The series of compounds with modified adamantane moiety was highly potent in cytotoxic effect on human lung carcinoma A549 cells (EC50 = 6–400 nM) and was active in affecting the microtubule arrays and induction of strong tubulin clusterization. In two other sets of compounds, the colchicine moiety of tubuloclustin was replaced by podophyllotoxin or combretastatin A-4. All combretastatin A-4 derivatives displayed noticeable cytotoxic activity (\(\hbox {EC}50=0.8{-}1.6\,\upmu \hbox {M}\)) but their effect on microtubules depended on the position of the linker attachment. Podophyllotoxin derivatives were also toxic to A549 cells (\(\hbox {EC}50=0.38{-}0.50\,\upmu \hbox {M}\)) and caused both microtubule depolymerization and some tubulin clustering. The data obtained gave additional evidence that the whole panel of C7-colchicine, podophyllotoxin and combretastatin derivatives could manifest clustering effect, and the strength of this effect correlated with cytotoxic activity of the compounds.     

Elastic capsules in shear flow: Analytical solutions for constant and time-dependent shear rates

We investigate the dynamics of microcapsules in linear shear flow within a reduced model with two degrees of freedom. In previous work for steady shear flow, the dynamic phases of this model, i.e. swinging, tumbling and intermittent behaviour, have been identified using numerical methods. In this paper, we integrate the equations of motion in the quasi-spherical limit analytically for time-constant and time-dependent shear flow using matched asymptotic expansions. Using this method, we find analytical expressions for the mean tumbling rate in general time-dependent shear flow. The capsule dynamics is studied in more detail when the inverse shear rate is harmonically modulated around a constant mean value for which a dynamic phase diagram is constructed. By a judicious choice of both modulation frequency and phase, tumbling motion can be induced even if the mean shear rate corresponds to the swinging regime. We derive expressions for the amplitude and width of the resonance peaks as a function of the modulation frequency.     

A hot cavity laser ion source at IGISOL

A development program is underway at the IGISOL (Ion Guide Isotope Separator On-Line) facility, University of Jyväskylä, to efficiently and selectively produce low-energy radioactive ion beams of silver isotopes and isomers, with a particular interest in N = Z ⁹⁴Ag . A hot cavity ion source has been installed, based on the FEBIAD (Forced Electron Beam Induced Arc Discharge) technique, combined with a titanium:sapphire laser system for selective laser ionization. The silver recoils produced via the heavy-ion fusion-evaporation reaction, ⁴⁰Ca(⁵⁸Ni, p3n)⁹⁴Ag , are stopped in a graphite catcher, diffused, extracted and subsequently ionized using a three-step laser ionization scheme. The performance of the different components of the hot cavity laser ion source is discussed and initial results using stable ^{107, 109}Ag are presented.     

From uncertainty to reward: BOLD characteristics differentiate signaling pathways

Background  

Reward value and uncertainty are represented by dopamine neurons in monkeys by distinct phasic and tonic firing rates. Knowledge about the underlying differential dopaminergic pathways is crucial for a better understanding of dopamine-related processes. Using functional magnetic resonance blood-oxygen level dependent (BOLD) imaging we analyzed brain activation in 15 healthy, male subjects performing a gambling task, upon expectation of potential monetary rewards at different reward values and levels of uncertainty.