Helicity amplitudes A1/2 and A3/2 for the D13(1520) resonance obtained from the gamma-->p-->-->ppi(0) Reaction

The helicity dependence of the gamma-->p-->-->ppi(0) reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the D13(1520) resonance and are used to determine its helicity amplitudes.     

Information Theory Applied to Parameter Inference of Pake Doublet Spectra

Magnetic resonance absorption lineshapes can have subtle dependencies on the model parameters that specify the lineshape. To quantify how the model parameters influence the lineshape, it is useful to study simple model systems for which analytical expressions are available. We propose that information theory is a useful tool to quantify how well model parameters may be inferred from a noisy signal. Information theory also allows us to assess the importance of missing parameters from an incomplete model. We do this by monitoring the magnitude of a partition function determined from a suitably defined probability mass function as the model parameters are varied. The optimum parameter set makes the partition function a maximum, which establishes a computable criterion for determining the best model parameter set. Given the availability of a partition function, one may define thermodynamic functions such as the entropy. The optimum parameter set in this interpretation corresponds to the state of maximum entropy. In this work, we observe that at sufficiently low signal to noise ratio, the entropy landscape has no clear maximum, while a related quantity, the Fisher information, always has a clear minimum at the optimum parameter set. The qualitative information we are able to gather from the entropy landscapes is also difficult to assess when the parameters are far from their optimum values, at least for the model system studied here.     

Evaluation of ‘east-to-west’ ether-forming strategies for the total synthesis of maoecrystal V

Model systems that evaluated different approaches to construct the central ether ring of maoecrystal V are described. Our first model systems attempted the ether formation using C–H functionalization reactions, which led to interesting rearrangements but none of the desired ether product. An intramolecular conjugate addition strategy was then explored that successfully formed the targeted C–O bond but resulted in the undesired stereochemistry.     

Ln(III) methyl and methylidene complexes stabilized by a bulky hydrotris(pyrazolyl)borate ligand

The reaction of Ln(AlMe(4))(3) with bulky hydrotris(pyrazolyl)borate (Tp(t)(Bu,Me))H proceeds via a sequence of methane elimination and C-H bond activation, affording unprecedented rare-earth metal ligand moieties including Ln(Me)[(micro-Me)AlMe(3)] and X-ray structurally characterized "Tebbe-like" Ln[(micro-CH(2))(2)AlMe(2)].     

Ultrafast changes of molecular crystal structure induced by dipole solvation

Femtosecond photoexcitation of organic chromophores in a molecular crystal induces strong changes of the electronic dipole moment via intramolecular charge transfer as is evident from transient vibrational spectra. The structural response of the crystal to the dipole change is mapped directly for the first time by ultrafast x-ray diffraction or diffuse scattering. Changes of diffracted and transmitted x-ray intensity demonstrate an angular rearrangement of molecules around excited dipoles following the 10 ps kinetics of charge transfer and leaving lattice plane spacings unchanged. Transient x-ray scattering is governed by solvation, masking changes of the chromophore molecular structure.     

Evaluation of VIDAS Salmonella (SLM) easy Salmonella method for the detection of Salmonella in a variety of foods: collaborative study

The VIDAS Salmonella (SLM) Easy Salmonella method is a specific enzyme-linked fluorescent immunoassay performed in the automated VIDAS instrument. The VIDAS Easy Salmonella method is a simple 2-step enrichment procedure, using pre-enrichment followed by selective enrichment in a newly formulated broth, SX2 broth. This new method was compared in a multilaboratory collaborative study to the U.S. Food and Drug Administration's Bacteriological Analytical Manual, Chapter 5 method for five food matrixes (liquid egg, vanilla ice cream, spinach, raw shrimp, and peanut butter) and the U.S. Department of Agriculture's Microbiology Laboratory Guidebook 4.04 method for deli turkey. Each food type was artificially contaminated with Salmonella at three inoculation levels. A total of 15 laboratories representing government, academia, and industry, throughout the United States, participated. In this study, 1583 samples were analyzed, of which 792 were paired replicates and 791 were unpaired replicates. Of the 792 paired replicates, 285 were positive by both the VIDAS and reference methods. Of the 791 unpaired replicates, 341 were positive by the VIDAS method and 325 were positive by the cultural reference method. A Chi-square analysis of each of the six food types was performed at the three inoculation levels tested. For all foods evaluated, the VIDAS Easy SLM method demonstrated results comparable to those of the reference methods for the detection of Salmonella.