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  • 1
    Language: English
    In: Journal of Non-Crystalline Solids, 2004, Vol.337(3), pp.232-240
    Description: Glasses with the basic compositions 10Na 2 O · 10CaO · x Al 2 O 3 · (80 − x )SiO 2 ( x =0, 5, 15, 25) and 16Na 2 O · 10CaO · x Al 2 O 3 · (74 − x )SiO 2 ( x =0, 5, 10, 15, 20) doped with 0.25–0.5 mol% SnO 2 were studied using square-wave-voltammetry at temperatures in the range from 1000 to 1600 °C. The voltammograms exhibit a maximum which increases linearly with increasing temperature. With increasing alumina concentration and decreasing Na 2 O concentration the peak potentials get more negative. Mössbauer spectra showed two signals attributed to Sn 2+ and Sn 4+ . Increasing alumina concentrations did not affect the isomer shift of Sn 2+ ; however, they led to increasing quadrupole splitting, while in the case of Sn 4+ both isomer shift and quadrupole splitting increased. A structural model is proposed which explains the effect of the composition on both the peak potentials and the Mössbauer parameters.
    Keywords: Engineering ; Chemistry ; Physics
    ISSN: 0022-3093
    E-ISSN: 1873-4812
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  • 2
    Language: English
    In: Chemistry - A European Journal, March, 2014, Vol.20(10), p.2913(12)
    Description: Byline: Dimitri Sakow, Dirk Baabe, Birte Boker, Olaf Burghaus, Markus Funk, Christian Kleeberg, Dirk Menzel, Clemens Pietzonka, Martin Broring Keywords: heterocorroles; iron; N ligands; porphyrinoids; spin state Abstract A first systematic study upon the preparation and exploration of a series of iron 10-thiacorroles with simple halogenido (F, Cl, Br, I), pseudo-halogenido (N.sub.3, I.sub.3) and solvent-derived axial ligands (DMSO, pyridine) is reported. The compounds were prepared from the free-base octaethyl-10-thiacorrole by iron insertion and subsequent ligand-exchange reactions. The small N.sub.4 cavity of the ring-contracted porphyrinoid results in an intermediate spin (i.s., S=3/2) state as the ground state for the iron(III) ion. In most of the investigated cases, the i.s. state is found unperturbed and independent of temperature, as determined by a combination of X-ray crystallography and magnetometry with .sub.1HaNMR-, EPR-, and Mossbauer spectroscopy. Two exceptions were found. The fluorido iron(III) complex is inhomogenous in the solid and contains a thermal i.s. (S=3/2)ahigh spin (h.s., S=5/2) crossover fraction. On the other side, the cationic bis(pyridine) complex resides in the expected low spin (l.s., S=1/2) state. Chemically, the iron 10-thiacorroles differ from the iron porphyrins mainly by weaker axial ligand binding and by a cathodic shift of the redox potentials. These features make the 10-thiacorroles interesting ligands for future research on biomimetic catalysts and model systems for unusual heme protein active sites. Author Affiliation: Institut fur Anorganische und Analytische Chemie (AAC), Technische Universitat Braunschweig, Hagenring 30, 38106 Braunschweig (Germany), Fax: (+49)531-391-5387 Fachbereich Chemie, Philipps-Universitat Marburg, Hans-Meerwein-Strasse, 5032 Marburg (Germany) Institut fur Physik der Kondensierten Materie (IPKM), Technische Universitat Braunschweig, Mendelssohnstrasse 3, 38106 Braunschweig (Germany) Supporting information: Additional Supporting Information may be found in the online version of this article As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. CAPTION(S): miscellaneous_information
    Keywords: Biomimetics -- Analysis ; Iron (Metal) -- Analysis ; Porphyrins -- Analysis ; Hemoproteins -- Analysis ; Pyridine -- Analysis
    ISSN: 0947-6539
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  • 3
    Language: English
    In: Journal of Plant Nutrition and Soil Science, October 2010, Vol.173(5), pp.644-653
    Description: Riparian forests are assumed to play a crucial role in the global carbon cycle. However, little data are available on C stocks of floodplains in comparison to other terrestrial ecosystems. In this study, we quantified the C stocks of aboveground biomass and soils of riparian vegetation types at 76 sampling sites in the Donau‐Auen National Park in Austria. Based on our results and a remotely sensed vegetation map, we estimated total C stocks. Carbon stocks in soils (up to 354 t ha within 1 m below surface) were huge compared to other terrestrial ecosystems. As expected, soils of different vegetation types showed different texture with a higher percentage of sandy soils at the softwood sites, while loamy soils prevailed at hardwood sites. Total C stocks of vegetation types were significantly different, but reflect differences in woody plant biomass rather than in soil C stocks. Mature hardwood and cottonwood forests proved to have significantly higher total C stocks (474 and 403 t ha, respectively) than young reforestations (217 t ha) and meadows (212 t ha). The C pools of softwood forests (356 t ha) ranged between those of hardwood/cottonwood forests and of reforestations/meadows. Our study proves the relevance of floodplains as possible C sinks, which should be increasingly taken into account for river management. Furthermore, we conclude that plant‐species distribution does not indicate the conditions of sedimentation and soil C sequestration over the time span of interest for the development of soil C stocks.
    Keywords: Carbon Stocks ; Organic Carbon ; Donau‐Auen National Park ; Fluvial Ecosystems ; Riparian Forest
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 4
    Language: English
    In: Journal of Non-Crystalline Solids, 15 October 2004, Vol.345-346, pp.203-207
    Description: Square-wave voltammetric and Mössbauer measurements have been carried out in soda-lime and alumosilicates doped with 0.25–3.0 mol% SnO . The Na O and Al O concentrations have been varied. Only Sn and Sn have been detected. In soda-lime-silicates, with increasing Na O concentration Sn is successively favored and the covalent character of the Sn –O bonds increases. By contrast, in alumosilicates the incorporation of Sn is favored with increasing Al O concentration. Here, the s-electron density increases. Sn possesses a fourfold coordination. Sn is incorporated in octahedral positions. Changes in the Al O concentration have the largest effect on the incorporation of tin in the investigated glasses.
    Keywords: Engineering ; Chemistry ; Physics
    ISSN: 0022-3093
    E-ISSN: 1873-4812
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  • 5
    Language: English
    In: Journal of Non-Crystalline Solids, 2003, Vol.318(1), pp.202-212
    Description: Glasses of the basic compositions x Na 2 O·(100− x )SiO 2 ( x =15, 20, 26 and 33 mol%) and x Na 2 O·10CaO·(90− x )SiO 2 ( x =10, 16, 20 and 26 mol%) doped with 0.25 mol% SnO 2 were studied using square-wave voltammetry in the temperature range from 1000 to 1600 °C. The peak potentials determined by voltammetry were found to decrease linearly with temperature. While the peak potentials of the soda-silicate glasses did not depend on the Na 2 O-content, those measured in the lime containing glasses decreased with increasing Na 2 O-concentration. The Mössbauer spectra of tin-doped soda-lime-silicate glasses showed two signals attributed to Sn 2+ and Sn 4+ . The isomer shift for Sn 2+ decreases with increasing Na 2 O-concentration, while for Sn 4+ the opposite effect was observed. Both, however, can be explained by an increasing covalent character of the Sn–O bonds with increasing sodium concentration. From isomer shifts and quadrupolar interactions it is concluded that Sn 4+ is incorporated in a distorted sixfold coordination with strongly ionic bonds. The redox chemistry of the Sn 2+ /Sn 4+ equilibrium and the incorporation of tin into the silicate network are further discussed.
    Keywords: Engineering ; Chemistry ; Physics
    ISSN: 0022-3093
    E-ISSN: 1873-4812
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  • 6
    Language: English
    In: Plant physiology, July 2004, Vol.135(3), pp.1150-61
    Description: Endocytosis is the internalization of plasma membrane proteins and lipids, extracellular molecules, fluids, particles, exosomes, viruses, and bacteria. Endocytic internalization is a conserved process for all eukaryotic cells that is required for diverse cellular functions. These include turnover
    Keywords: Plant Physiological Phenomena ; Actins -- Physiology ; Cytoskeleton -- Physiology ; Endocytosis -- Physiology ; Plants -- Ultrastructure
    ISSN: 0032-0889
    E-ISSN: 15322548
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  • 7
    In: International Journal of Microwave and Wireless Technologies, 2013, Vol.5(1), pp.85-90
    Description: A general purpose two-channel Frequency modulated continuous wave (FMCW)-sensor in E-band is extended to a digital-beam-forming (DBF) system. The hardware extension contains a transmit multiplexer, which allows switching of the (DBF) transmit signal of the sensor to any of 32 linearly arranged waveguide antennae. To maintain the spatial sampling condition by λ/2 element distance, the antenna ports are arranged in the E-plane. The ports can directly radiate or serve as primary radiators of a cylindrical dielectric lens focusing in the H-plane. By realizing the hardware extension based on a metal-backed substrate, some novel radio frequency (RF) structures became necessary. One of these structures is a special twisting microstrip-to-waveguide-transition to connect the switching matrix to waveguide ports arranged in the E-plane. Key elements of the multiplexer are commercially available pin-diode-based MMIC-switches in microstrip technology. To lower the inductance of the interconnects, they are embedded in cavities in the metal-backed RF-substrate. RF interconnects between the sensor and the extension are all done with waveguide ports. Further interconnects between the module and the extension are low-frequency or digital and are led via cables and removable plugs. Both module and extension can be powered separately. This gives an easily mountable extension for making a two-dimensional (2D) DBF sensor out of a 1D FMCW-sensor.
    Keywords: Industrial And Engineering Paper; Radar Architecture And Systems; Radar Applications
    ISSN: 1759-0787
    E-ISSN: 1759-0795
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  • 8
    Language: English
    In: Journal of Magnetic Resonance, Feb, 2013, Vol.227, p.35(4)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jmr.2012.11.016 Byline: Enrico Chiavazza (a)(b), Eugen Kubala (a)(c), Concetta V. Gringeri (a)(d), Stephan Duwel (a)(e)(f), Markus Durst (a)(e)(f), Rolf F. Schulte (a), Marion I. Menzel (a) Keywords: Nuclear spin relaxation; Scalar coupling; Spin-lattice relaxation time; Dissolution DNP; Hyperpolarization;.sup.13C MR Spectroscopy Abstract: Display Omitted Author Affiliation: (a) GE Global Research, Munich, Germany (b) Molecular Imaging Center, Department of Chemistry, University of Turin, Turin, Italy (c) Johannes Kepler University, Linz, Austria (d) Nuklearmedizinische Klinik im Klinikum Rechts der Isar, Technische Universitat Munchen, Garching, Germany (e) Institute of Medical Engineering, Technische Universitat Munchen, Garching, Germany (f) Department of Chemistry, Technische Universitat Munchen, Garching, Germany Article History: Received 1 October 2012; Revised 14 November 2012
    Keywords: Geomagnetic Fields
    ISSN: 1090-7807
    Source: Cengage Learning, Inc.
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  • 9
    Language: English
    In: Journal of the American Chemical Society, 08 July 2015, Vol.137(26), pp.8475-83
    Description: Caseinolytic protease P (ClpP) represents a central bacterial degradation machinery that is involved in cell homeostasis and pathogenicity. The functional role of ClpP has been studied by genetic knockouts and through the use of beta-lactones, which remain the only specific inhibitors of ClpP discovered to date. Beta-lactones have served as chemical tools to manipulate ClpP in several organisms; however, their potency, selectivity and stability is limited. Despite detailed structural insights into the composition and conformational flexibility of the ClpP active site, no rational efforts to design specific non-beta-lactone inhibitors have been reported to date. In this work, an unbiased screen of more than 137 000 compounds was used to identify five phenyl ester compounds as highly potent ClpP inhibitors that were selective for bacterial, but not human ClpP. The potency of phenyl esters largely exceeded that of beta-lactones in ClpP peptidase and protease inhibition assays and displayed unique target selectivity in living S. aureus cells. Analytical studies revealed that while phenyl esters are cleaved like native peptide substrates, they remain covalently trapped as acyl-enzyme intermediates in the active site. The synthesis of 36 derivatives and subsequent structure-activity relationship (SAR) studies provided insights into conserved structural elements that are important for inhibition potency and acylation reactivity. Moreover, the stereochemistry of a methyl-substituent at the alpha position to the ester, resembling amino acid side chains in peptide substrates, impacted ClpP complex stability, causing either dissociation into heptamers or retention of the tetradecameric state. Mechanistic insights into this intriguing stereo switch and the phenyl ester binding mode were obtained by molecular docking experiments.
    Keywords: Endopeptidase Clp -- Metabolism ; Enzyme Inhibitors -- Chemistry ; Escherichia Coli -- Enzymology ; Escherichia Coli Proteins -- Metabolism ; Esters -- Chemistry ; Isoenzymes -- Chemistry ; Kallikreins -- Chemistry ; Staphylococcus Aureus -- Enzymology
    ISSN: 00027863
    E-ISSN: 1520-5126
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  • 10
    Language: English
    In: BMC microbiology, 04 September 2013, Vol.13, pp.198
    Description: The lipopolysaccharide (LPS) is the major immuno-dominant antigen of all Legionella species including L. pneumophila. Its diversity is the basis for the classification of L. pneumophila into serogroups and monoclonal subgroups and is thought to be involved in strain specific virulence. The understanding of the genetic basis of the LPS-antigen is incomplete. Thus, we analyzed the genetic locus involved in LPS-biosynthesis of L. pneumophila serogroup 1 (Sg1) strains with the focus on strain specific gene composition. The LPS-biosynthesis loci of 14 L. pneumophila Sg1 strains comprise two distinct regions: A 15 kb region containing LPS-biosynthesis genes that can be found in all L. pneumophila strains and a Sg1-specific 18 kb region. The 15 kb region is highly conserved among Sg1 strains as reflected by high homologies of single ORFs and by a consistent ORF arrangement. In contrast, the Sg1 specific 18 kb region is variable and partially disrupted by phage related genes. We propose that the region spanning from ORF 6 to ORF 11 of the Sg1-specific region is likely involved in late LPS-modification. Due to the high variability of this small region and various combinations of single ORFs within this region a strain specific LPS-structure could be synthesized including modifications of legionaminic acid derivates. Our data clearly demonstrate that the gene structure of the LPS-biosynthesis locus of L. pneumophila Sg1 strains show significant interstrain variability. These data can be used for further functional analysis of the LPS synthesis to understand pathogenesis and reactivity with monoclonal antibodies. Moreover, variable but strain specific regions can serve as basis for the development of novel genotyping assays.
    Keywords: Genetic Loci ; Genetic Variation ; Biosynthetic Pathways -- Genetics ; Legionella Pneumophila -- Genetics ; Lipopolysaccharides -- Biosynthesis
    E-ISSN: 1471-2180
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