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Abstract: MOLE (mining, organizing, and logging experiments) has been developed to meet the growing data management and target tracking needs of molecular biologists and protein crystallographers. The prototype reported here will become a Laboratory Information Management System (LIMS) to help protein scientists manage the large amounts of laboratory data being generated due to the acceleration in proteome research and will furthermore facilitate collaborations between groups based at different sites. To achieve this, MOLE is based on the data model for protein production devised at the European Bioinformatics Institute (Pajon A, et al., Proteins in press). (C) 2004 Wiley-Liss, Inc.
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Feb 2005
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Theoretical Physics
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Abstract: Quantum-mechanical correlations, or the quantum entanglement. of nuclear spin and spatial degrees of freedom can be observed with neutron scattering. The underlying concepts in quantum mechanics are discussed in the context of two recent experiments, which utilize the total scattering and the Compton scattering of neutrons.
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Mar 2005
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Abstract: The zinc Schlenk equilibrium, little used since it was first described in 1966, has been promoted through the addition of methylaluminoxane (MAO) to maximize the yield of ZnR2 from deleterious RZnCl by-products. This process allows an SN2?-addition approach to the preparation of chiral ?,?-disubstituted ?-methylenepropionates with high enantioselectivity (see scheme).
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Mar 2005
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Abstract: High-pressure recrystallisation of aqueous and methanolic solutions of piracetam (2-oxo-pyrrolidineacetamide) contained in a diamond-anvil cell at pressures of 0.07–0.4 GPa resulted in the formation of a new high-pressure polymorph of piracetam that has been characterised by in situ X-ray diffraction. The molecular packing arrangement of the new form is very different from those of forms I, II, and III, and the piracetam molecules also adopt a very different conformation in this new phase. Depressurisation to ambient pressure resulted in the formation of form II via a single-crystal to single-crystal transition. By contrast, crystallisation of piracetam from water at ambient pressure resulted in the formation of a new monohydrate of piracetam, which has been characterised by single crystal X-ray diffraction.
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Mar 2005
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Theoretical Physics
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Abstract: The few electrons in valence states of a material participate in many of its physical properties, including both structural and transport properties. In the diffraction of X-rays, or neutrons, valence electrons can lead to weak Bragg reflections that are extremely sensitive signatures of their charge and magnetic degrees of freedom. In this regard, diffraction instruments supplied with X-rays from a synchrotron source are particularly useful because the brightness, tuneability and polarization of the X-rays are all helpful in making valuable observations. The data obtained from Bragg diffraction can be analyzed on the basis of an atomic model, which has the virtue that it can be used as a common platform for the analysis of X-ray and neutron diffraction and, in addition, the analysis of observations made with X-ray absorption, NMR, EPR, muon and Mossbauer spectroscopies. We present the salient features for the calculation of structure factors based on an atomic model and applied to the analysis of Bragg diffraction by non-magnetic and magnetic materials, with an emphasis on resonant X-ray Bragg diffraction. The presentation contains a new treatment of parity-odd events found in the mixed electric dipole-electric quadrupole channel of scattering. In addition we discuss the complementary observation of dichroic signals, including natural circular and magnetochiral dichroism. The survey of available analytical tools is complemented by a series of worked examples demonstrating the application of the formalism to different materials with different crystal structures and resonant ions: dysprosium borocarbide (DyB2C2), vanadium sesquioxide (V2O3), gadolinium tetraboride (GdB4), chromium sesquioxide (Cr2O3), haematite and perovskite-type manganites.
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Apr 2005
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Abstract: Das Zink-Schlenk-Gleichgewicht, das seit seiner ersten Beschreibung 1966 wenig genutzt wurde, wird durch die Zugabe von Methylaluminoxan (MAO) begünstigt, das die Ausbeute an ZnR2 ausgehend von schädlichen RZnCl-Begleitprodukten maximiert. So wurde eine SN2′-Addition als hoch enantioselektiver Zugang zu chiralen β,β-disubstituierten α-Methylenpropionaten möglich (siehe Schema).
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Apr 2005
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Mechanical Engineering
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May 2005
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RF
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Abstract: We present the first RF measurements of the IOT based 300 kW 500 MHz amplifier for the Diamond Light Source. Four 80 kW IOTs are combined using a waveguide combiner to achieve the RF requirement of up to 300 kW for each of three superconducting cavities for the main storage ring. The IOTs are protected by a full power circulator and a 300 kW ferrite RF load. This is the first time IOTs will be used for a synchrotron light source. This paper gives an overview of the design of the Thales amplifiers and IOTs with commissioning results, including measurements of key components and overall RF performance, following factory tests and the installation of the first unit.
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May 2005
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Theoretical Physics
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Abstract: X-ray diffraction measurements on a-solid oxygen under an applied magnetic field are reported. The volume of alpha-solid O-2 is found to expand with increasing magnetic field: the lattice constants a and b elongate, while the lattice constant c and the angle are almost independent of the magnetic field. The maximum volume expansion observed is about 1% under a 7.5 T field, which is a giant effect compared to the volume change observed in ferromagnetic metals, such as Fe, Co and Ni. This finding indicates that a spin-dependent intermolecular potential is essential in determining the structure of alpha-solid O-2. The experimental results conform with predictions based on a magneto-elastic interaction derived from an antiferromagnetic exchange coupling of O-2 spins.
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May 2005
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Abstract: We have studied bilayers and trilayers of FePd thin-film alloys, where each of the constituting layers has a different magnetic anisotropy, as controlled by the growth conditions. The competition between the magnetocrystalline anisotropy and the shape anisotropy in these films leads to the formation of stripe domains with a period of ?100nm , which has been imaged by magnetic force microscopy (MFM). The average magnetic anisotropy has been obtained from the in-plane and perpendicular magnetic field dependence, measured using vibrating sample magnetometry (VSM). We measured the soft x-ray resonant magnetic scattering (SXRMS) at the Fe L 3 edge using ? linearly polarized light, which is sensitive to the magnetization profile in the layers. The magnetic configuration of the layer systems was modeled using micromagnetic software (GL-FFT, ©CNRS). The results of the micromagnetic modeling were used for a numerical simulation of the reflectivity scan and the magnetic rod scans of the SXRMS. This allowed us to determine parameters, such as the lateral roughness, the magnetic period, the magnetic correlation length, and the magnetic layer thickness. The good agreement obtained with the experimental results demonstrates that SXRMS provides in-depth information that cannot be obtained from either MFM or VSM.
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May 2005
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