<Emphasis FontCategory=NonProportional>WHIZARD</Emphasis>—simulating multi-particle processes at LHC and ILC

We describe the universal Monte-Carlo (parton-level) event generator WHIZARD (), version 2. The program automatically computes complete tree-level matrix elements, integrates them over phase space, evaluates distributions of observables, and generates unweighted partonic event samples. These are showered and hadronized by calling external codes, either automatically from within the program or via standard interfaces. There is no conceptual limit on the process complexity; using current hardware, the program has successfully been applied to hard scattering processes with up to eight particles in the final state. Matrix elements are computed as helicity amplitudes, so spin and color correlations are retained. For event generation, processes can be concatenated with full spin correlation, so factorized approximations to cascade decays are possible when complete matrix elements are not desired. The Standard Model, the MSSM, and many alternative models such as Little Higgs, anomalous couplings, or effects of extra dimensions or noncommutative SM extensions have been implemented. Using standard interfaces to parton shower and hadronization programs, WHIZARD covers physics at hadron, lepton, and photon colliders.     

A combined Kirchhoff–Master equation approach to electronic transport in one-dimensional molecular conductors

We discuss classical one-dimensional conductivity problems using Kirchhoff’s law comprising resistor network nodes that can only be occupied by a limited number of charge carriers, leading to the formulation of combined Kirchhoff–Master equations (KMEs) of electronic transport. For illustrative purposes, the equations are solved for simple two site systems; and we present a numerical solution by means of a Monte Carlo method for arbitrary systems. As an example, the procedure is applied to describe DNA charge transfer through a nanojunction at ambient conditions in the regime of small external voltages.     

Thermoanalytical and structural characterization of fluoridated calcium phosphates prepared in anhydrous alcohols

A thermoanalytical, morphological, and structural study of fluoridated calcium phosphates that were prepared by different variants of a synthesis in anhydrous alcohols is reported. The obtained materials were neither fully amorphous nor single-phased crystalline, and their nature considerably depended on the synthesis conditions. In all cases, the retention of significant amounts of solvent in the solid product was observed. A complete removal of the solvent was only possible by heating to temperatures above ~573–673 K which resulted in variations in the elemental composition, phase changes, and an increase of the crystallinity. Consequently, this synthesis in anhydrous alcohols is not a viable route to obtain materials with a defined crystallinity and stoichiometry.     

Total syntheses of the thiopeptides amythiamicin C and D

The thiopeptides amythiamicin C and D were synthesized by employing amide bond formation, a Stille cross-coupling reaction, and two Negishi cross-coupling reactions as key transformations. The central 2,3,6-trisubstituted pyridine ring of the target compounds was introduced as a 2,6-dibromo-3-iodopyridine, which was selectively metalated at the 3-position and connected to the complete Southern fragment of the amythiamicins by a Negishi cross-coupling. For the synthesis of amythiamicin C, this step was followed by a Negishi cross-coupling at C-6 of the pyridine core. Subsequent attachment of the Eastern fragment was achieved by amide bond formation and macrolactam ring closure by a Stille cross-coupling at C-2. The Eastern bithiazole fragment of the amythiamins was constructed also by regioselective metalation and cross-coupling reactions. The pivotal step involved the diastereoselective addition of 4-bromothiazole-2-magnesium bromide to a chiral sulfinyl imine. For the synthesis of amythiamicin D, the order of cross-coupling at C-6, amide bond formation, and cross-coupling at C-2 was changed. The amide bond formation to the Eastern fragment was performed first and it was subsequently attempted to close the macrolactam by an intramolecular regioselective Stille cross-coupling at C-2. Despite the low regioselectivity of this reaction it paved the way to the immediate completion of the amythiamicin D synthesis when followed by a Negishi cross-coupling at C-6 with 2-zincated methyl thiazole-5-carboxylate.     

Complete control of regioselectivity in the intramolecular [2 + 2] photocycloaddition of 2-alkenyl-3(2H)-furanones by the length of the side chain

The 2-(omega-alkenyl)-substituted 2-methyl-3(2H)-furanones 2a and 2b were prepared from biacetyl (3) in four reaction steps and in overall yields of 20% and 21%, respectively. They underwent a clean intramolecular [2 + 2] photocycloaddition upon irradiation at lambda = 350 nm. Whereas compound 2a reacted in the expected manner and yielded 7-oxabicyclo[3.2.1.0(3,6)]octane 7 (87% yield), the regioselectivity in the photocycloaddition of compound 2b was completely reversed. The reaction led to compound 8 (92% yield) with the unusual 9-oxabicyclo[4.2.1.0(3,8)]nonane skeleton, the structure of which was established by single-crystal X-ray crystallography.