Atom interferometer based on phase coherent splitting of Bose-Einstein condensates with an integrated magnetic grating

We report the phase coherent splitting of Bose-Einstein condensates by means of a phase grating produced near the surface of a microelectronic chip. A lattice potential with a period of 4 mum is generated by the superposition of static and oscillating magnetic fields. Precise control of the diffraction is achieved by controlling the currents in the integrated conductors. The interference of overlapping diffraction orders is observed after 8 ms of propagation in a harmonic trap and subsequent ballistic expansion of the atomic ensemble. By analyzing the interference pattern we show a reproducible phase relation between the diffraction orders with an uncertainty limited by the resolution of the diffraction grating.     

Darstellung und Eigenschaften von Dibromotrachloro-u-methylen- diantimonaten(III) and Hexabromotetrachloro-u-methylen-diantimonaten(V)

Preparation and Properties of Dibromotetrachloro-u-methylene-diantimonates(III) and Hexabromotetrachloro-u-methylene-diantimonates(V) The complex salts (R₄E)₂ [Br₃Cl₂Sb]₂ CH₂ (R₄E = Et₄N, Ph₄P, Ph₄As, Ph₄Sb) are obtained by the reaction of [Cl₂Sb]₂ with R₄ EBr in dichloromethane. The oxidation of the new compounds with Br₂ at ?78°C, in dichloromethane, leads to the corresponding complex salts of pentavalent antimony (R₄E)₂[Br₃Cl₂Sb]₂CH₂.     

One‐dimensional small‐angle X‐ray scattering tomography of dip‐coated polyamide 6 monofilaments

A synchrotron study is presented in which the concept of one‐dimensional tomographic reconstruction of small‐angle X‐ray scattering patterns is applied to investigate polyamide 6 monofilaments, dip‐coated with alumina particles. The filaments are scanned with a focused synchrotron beam and the resulting scattering patterns are recorded with a PILATUS 2M detector. The reconstructed sequence of SAXS images reflects the local nanostructure variation along the filament radius. In particular, the influence of coating process parameters on the polyamide 6 is investigated.     

Unusually weak binding interactions in tetrazole-amidine complexes

[reaction: see text] Tetrazoles frequently replace carboxylic acids in pharmaceutical drugs. However, while the binding modes of tetrazolate and carboxylate anions in amidinium complexes turns out to be similar, the association constant of the former is 2-3 orders of magnitude smaller in DMSO. Crystal structures revealed that the N...H-N hydrogen bonds in amidinium tetrazolates are bent (162 degrees and 169 degrees ) and noticeably longer (N...N 2.96 A) than corresponding hydrogen bonds in both amidinium carboxylates and ammonium tetrazolates.     

Investigation of Contemporary Forgeries of Ancient Silver Coins

Four ancient Roman silver coins from about 200 BC to 200 AD, mainly contemporary forgeries, were investigated in order to deduce the methods and materials used in the production of the forged coins. Special attention was devoted to a Denar from the Roman Republic, a C. Mamilius Limetanus denarius serratus (approx. 82 BC), because an original coin (pure silver) as well as a forgery were available. These coins both show serrated edges, i.e. notches all around with irregular spacing. A combination of microbeam analytical techniques was applied: Scanning Electron Microscopy (SEM), Electron Probe Micro Analysis (EPMA) and Secondary Ion Mass Spectrometry (SIMS). Some of the counterfeits consist of a base metal core plated with silver. The serrated Denar exhibits a plating layer with a thickness of approx. 100µm as determined by SEM and SIMS. This is an indication for foil silvering, as well as the apparent overlapping of the outer layer in one particular area.     

Conformational Analysis and CD Calculations of Methyl‐Substituted 13‐Tridecano‐13‐lactones

Conformational models covering an energy range of 3 kcal/mol were calculated for (13S)‐tetradecano‐13‐lactone ( 3 ), (12S)‐12‐methyltridecano‐13‐lactone ( 4 ), and (12S,13R)‐12‐methyltetradecano‐13‐lactone ( 8 ), starting from a semiempirical Monte‐Carlo search with AM1 parametrization, and subsequent optimization of the 100 best conformers at the 6‐31G*/B3LYP and then the TZVP/B3LYP level of density‐functional theory. CD Spectra for these models were calculated by the time‐dependent DFT method with the same functional and basis sets as for the ground‐state calculations and Boltzmann weighting of the individual conformers. The good correlation of the calculated and experimental spectra substantiates the interpretation of these conformational models for the structure–odor correlation of musks. Furthermore, the application of the quadrant rule in the estimation of the Cotton effect for macrolide conformers is critically discussed.     

Odds and Trends: Recent Developments in the Chemistry of Odorants

Fragrance chemistry is, together with the closely related area of flavor chemistry, one of the few domains, if not the only one, in which chemists can immediately experience structure–activity relationships. This review presents structure–odor correlations and olfactophore models for the main odor notes of perfumery: “fruity”, “marine”, “green”, “floral”, “spicy”, “woody”, “amber”, and “musky”. New trendsetters and so‐called captive odorants of these notes are introduced, and recent activities and highlights in fragrance chemistry are summarized. The design of odorants, their chemical synthesis, and their use in modern perfumery is discussed. Our selection is guided and illustrated by creative fragrances, and features new odorants which encompassed current trends in perfumery. New odorants for grapefruit and blackcurrant, for galbanum, and leafy top notes are presented. Compounds with fashionable marine, ozonic, and aquatic facets are treated, as well as new odorants for classical lily‐of‐the‐valley, rose, and jasmine accords. Compounds with sweet and spicy tonalities are also discussed, as are the most recent developments for woody notes such as sandalwood and vetiver. We conclude with musky and ambery odorants possessing uncommon or unusual structural features. Some odor trends and effects are illustrated by microencapsulated fragrance samples, and areas where there is need for the development of new synthetic materials and methodologies are pointed out. Thus, chemists are invited to explore fragrance chemistry and participate in the design and synthesis of new odorants. This review gives the latest state of the art of the subject.     

Bayesian Error Propagation for a Kinetic Model of n‐Propylbenzene Oxidation in a Shock Tube

We apply a Bayesian parameter estimation technique to a chemical kinetic mechanism for n‐propylbenzene oxidation in a shock tube to propagate errors in experimental data to errors in Arrhenius parameters and predicted species concentrations. We find that, to apply the methodology successfully, conventional optimization is required as a preliminary step. This is carried out in two stages: First, a quasi‐random global search using a Sobol low‐discrepancy sequence is conducted, followed by a local optimization by means of a hybrid gradient‐descent/Newton iteration method. The concentrations of 37 species at a variety of temperatures, pressures, and equivalence ratios are optimized against a total of 2378 experimental observations. We then apply the Bayesian methodology to study the influence of uncertainties in the experimental measurements on some of the Arrhenius parameters in the model as well as some of the predicted species concentrations. Markov chain Monte Carlo algorithms are employed to sample from the posterior probability densities, making use of polynomial surrogates of higher order fitted to the model responses. We conclude that the methodology provides a useful tool for the analysis of distributions of model parameters and responses, in particular their uncertainties and correlations. Limitations of the method are discussed. For example, we find that using second‐order response surfaces and assuming normal distributions for propagated errors is largely adequate, but not always.     

Discovery of Highly Selective Alkyne Semihydrogenation Catalysts Based on First‐Row Transition‐Metallated Porous Organic Polymers

Five different first‐row transition metal precursors (V^III, Cr^III, Mn^II, Co^II, Ni^II) were successfully incorporated into a catechol porous organic polymer (POP) and characterized using ATR‐IR and XAS analysis. The resulting metallated POPs were then evaluated for catalytic alkyne hydrogenation using high‐throughput screening techniques. All POPs were unexpectedly found to be active and selective catalysts for alkyne semihydrogenation. Three of the metallated POPs (V, Cr, Mn) are the first of their kind to be active single‐site hydrogenation catalysts. These results highlight the advantages of using a POP platform to develop new catalysts which are otherwise difficult to achieve through traditional heterogeneous and homogeneous routes.