Prominent higher-order contributions to electronic recombination

Intershell higher-order (HO) electronic recombination is reported for highly charged Ar, Fe, and Kr ions, where simultaneous excitation of one K-shell electron and one or two additional L-shell electrons occurs upon resonant capture of a free electron. For the mid-Z region, HO resonance strengths grow unexpectedly strong with decreasing atomic number Z (∝Z(-4)), such that, for Ar ions the 2nd-order overwhelms the 1st-order resonant recombination considerably. The experimental findings are confirmed by multiconfiguration Dirac-Fock calculations including hitherto neglected excitation pathways.     

Streaking at high energies with electrons and positrons

A detection scheme for characterizing high-energy γ-ray pulses down to the zeptosecond timescale is proposed. In contrast to existing attosecond metrology techniques, our method is not limited by atomic shell physics and therefore capable of breaking the MeV photon energy and attosecond time-scale barriers. It is inspired by attosecond streak imaging, but builds upon the high-energy process of electron-positron pair production in vacuum through the collision of a test pulse with an intense laser pulse. We discuss necessary conditions to render the scheme feasible in the upcoming Extreme Light Infrastructure laser facility.     

Modeling and benchmark data set for the inhibition of c-Jun N-terminal kinase-3

The goal of this paper is to present and describe a novel 2D- and 3D-QSAR (quantitative structure-activity relationship) binary classification data set for the inhibition of c-Jun N-terminal kinase-3 with previously unpublished activities for a diverse set of compounds. JNK3 is an important pharmaceutical target because it is involved in many neurological disorders. Accordingly, the development of JNK3 inhibitors has gained increasing interest. 2D and 3D versions of the data set were used, consisting of 313 (70 actives) and 249 (60 actives) compounds, respectively. All compounds, for which activity was only determined for the racemate, were removed from the 3D data set. We investigated the diversity of the data sets by an agglomerative clustering with feature trees and show that the data set contains several different scaffolds. Furthermore, we show that the benchmarks can be tackled with standard supervised learning algorithms with a convincing performance. For the 2D problem, a random decision forest classifier achieves a Matthew's correlation coefficient of 0.744, the 3D problem could be modeled with a Matthew's correlation coefficient of 0.524 with 3D pharmacophores and a support vector machine. The performance of both data sets was evaluated within a nested 10-fold cross-validation. We therefore suggest that the data set is a reasonable basis for generating QSAR models for JNK3 because of its diverse composition and the performance of the classifiers presented in this study.     

Fast wheat variety classification by capillary gel electrophoresis-on-a-chip after single-step one-grain high molecular weight glutenin extraction

Wheat variety identification based on one-step single-grain wheat extraction and fast capillary gel electrophoresis-on-a-chip (CGE-on-a-chip) analyses was evaluated for 15 different wheat varieties grown in Austria. The results of the capillary-based separation system were compared to the internationally accepted method from the International Union for the Protection of New Varieties of Plants which is based on time-consuming sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Comparable protein patterns were observed making the CGE-on-a-chip system a promising tool for high-throughput analysis in food control. For the development of a robust method protein extraction, shelf life of wheat extracts and the instrument’s variability were evaluated. It turned out that a one-step single-grain wheat extraction allowed the sample to be stored at 4 °C for up to 4 weeks without losing any valuable protein information. Furthermore, the technical variation of the whole method is very low making the biological variation of the selected wheat grains the only uncertain factor. Additionally, two unsupervised statistical methods (hierarchical cluster analysis and principal component analysis) were used for variety identification. Identification was successful for a reduced data set of 14 samples from five different wheat varieties making the combination of CGE-on-a-chip analysis of one-step single-grain extraction in combination with automatic data evaluation a promising tool for fast wheat differentiation (within a day).     

Direct C-4 arylation of crotonaldehyde with arenediazonium tetrafluoroborates

Arenediazonium tetrafluoroborates react with crotonaldehyde (2-butenal) in methanol in the presence of catalytic amounts of Pd(OAc)₂ to yield mainly 4,4-dimethoxy-1-butenylarenes. In most of the examples studied, small amounts of an isomeric byproduct were formed, presumably 3,3-dimethoxy-1-methylenepropylarenes. Because crotonaldehyde and arenediazonium salts are cheap and readily available, this reaction is a convenient access to protected 4-arylbutenals.     

Biocatalytic organic synthesis of optically pure (S)-scoulerine and berbine and benzylisoquinoline alkaloids

A chemoenzymatic approach for the asymmetric total synthesis of the title compounds is described that employs an enantioselective oxidative C-C bond formation catalyzed by berberine bridge enzyme (BBE) in the asymmetric key step. This unique reaction yielded enantiomerically pure (R)-benzylisoquinoline derivatives and (S)-berbines such as the natural product (S)-scoulerine, a sedative and muscle relaxing agent. The racemic substrates rac-1 required for the biotransformation were prepared in 4-8 linear steps using either a Bischler-Napieralski cyclization or a C1-Cα alkylation approach. The chemoenzymatic synthesis was applied to the preparation of fourteen enantiomerically pure alkaloids, including the natural products (S)-scoulerine and (R)-reticuline, and gave overall yields of up to 20% over 5-9 linear steps.     

Isotropic proton-density-weighted high-resolution MRI for volume measurement of reconstructed orbital fractures--a comparison with multislice CT

Objective

The cause of enophthalmos as a late complication after orbital reconstruction is poorly investigated. Multislice CT (MSCT) is usually employed for its assessment, in spite of limitations regarding soft tissue depiction/imaging, as well as the implication of radiation and production of artifacts. Magnetic resonance imaging (MRI) has been shown to be a valuable alternative. The aim of this study was to establish a bony and soft tissue orbital volume calculation method based on different high-resolution MRI sequences compared to MSCT.

Materials and Methods

Thirty-seven patients were included in this prospective study investigating the origin of enophthalmos present 3–4 months after complex orbital reconstruction. Morphological and dimensional changes of the orbit, eye globes, extraocular muscles and fat content were investigated 3–4 months after surgery. To assess the site and size of bony and soft tissue changes in the traumatized orbits, we used MSCT and MR images as well as corresponding 3-D reconstructions.

Results

All enophthalmic orbits revealed a significant bony volume increase compared to the contralateral side as well as a reduced sagittal eye projection. Mean orbital volume enlargements of 1.0 cm³ lead to 0.93 mm enophthalmos (P<.05). Hardly any fatty atrophy could be depicted by the different MRI techniques.

Conclusions

For soft tissue depiction of the orbit, MRI was superior to MSCT. Particularly, proton density weighting proved to be the best sequence for soft tissue volume segmentation, allowing determination of the cause and degree of posttraumatic enophthalmos in reconstructed orbits.     

Resonant recombination at ion storage rings: a conceptual alternative for isotope shift and hyperfine studies

Sharp resonant structures in the cross section of the atomic electron-ion collision process of dielectronic recombination are exploited to study isotope shifts and hyperfine interaction of heavy highly-charged ions. This novel approach provides a conceptual alternative to existing methods. In this contribution, we present a series of measurements, which we performed at the heavy ion storage ring ESR of the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany. In a first experiment the stable isotopes A = 142 and A = 150 of three-electron neodymium ^ANd^57?+? were studied. Isotope shifts of dielectronic resonances associated with 2s???2p _j (j?=?1/2, 3/2) transitions were extracted from the measured data. The evaluation of the energy shift was performed within a full QED framework and yielded a change in the mean-square charge radius of $^{142,150}\delta \langle r^2 \rangle = -1.36(1)(3)$  fm². At GSI, in addition to the investigation of stable isotopes unstable species can be artificially synthesized and studied. Radioisotopes produced in-flight from fragmentation of a ²³⁸U primary beam were injected into the ESR and were subsequently separated by their mass-to-charge ratio. This enabled us to perform first DR experiments with the exotic nuclei ²³⁷U^89?+? (Z = 92 )and ²³⁴Pa^88?+? (Z = 91).     

Ternary Rare Earth Metal Palladium and Platinum Aluminides R4Pd9Al24 and R4Pt9Al24

The fifteen intermetallic compounds R₄Pd₉Al₂₄ (R = Gd–Tm) and R₄Pt₉Al₂₄ (R = Y, Gd–Lu) were prepared by reaction of the elemental components. Their crystal structure was determined from single-crystal X-ray data of Er₄Pt₉Al₂₄. It is pseudo-trigonal with triclinic symmetry: P 1, a = b = 747.5(2) pm, c = 1306.7(4) pm, α = 100.99(2)°, β = 95.47(2)°, γ = 60.00(3)°, Z = 1, R = 0.052 for 2593 structure factors and 110 variable parameters. The structure is closely related to that of Y₂Co₃Ga₉. Both may be described as stacking variants of each other. They consist of layers of the compositions PtAl₂ (CoGa₂), and Er₂Al₃ (Y₂Ga₃), designated A and B, respectively. These layers are stacked in the five- and four-layer sequences ABAAB (Er₄Pt₉Al₂₄) and ABAB (Y₂Co₃Ga₉). The layers PtAl₂ and CoGa₂ are similar to the hexagonal close packed layers in the TiSi₂-, CrSi₂-, and MoSi₂-type structures. The structure of Er₄Pt₉Al₂₄ contains a monoclinic subcell, where the layers Er₂Al₃ are disordered. A partial disorder of this kind, which could be ascribed to twinning or to the intergrowth with another stacking variant, was found during the structure refinement of the isotypic compound Y₄Pt₉Al₂₄: a = b = 749.0(2) pm. c = 1309.3(4) pm, α = 100.99(2)°, β = 95.48(2)°, γ = 60.00(3)°, R = 0.031 for 1435 structure factors and 128 variable parameters.