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11.
Jonas Baumann Christian Krnig Theresa Staufer Christopher Schlesiger Oliver Schmutzler Florian Grüner Wolfgang Malzer Birgit Kanngießer 《International journal of molecular sciences》2022,23(9)
Trace elements, functionalized nanoparticles and labeled entities can be localized with sub-mm spatial resolution by X-ray fluorescence imaging (XFI). Here, small animals are raster scanned with a pencil-like synchrotron beam of high energy and low divergence and the X-ray fluorescence is recorded with an energy-dispersive detector. The ability to first perform coarse scans to identify regions of interest, followed by a close-up with a sub-mm X-ray beam is desirable, because overall measurement time and X-ray dose absorbed by the (biological) specimen can thus be minimized. However, the size of X-ray beams at synchrotron beamlines is usually strongly dependent on the actual beamline setup and can only be adapted within specific pre-defined limits. Especially, large synchrotron beams are non-trivial to generate. Here, we present the concept of graphite-based, convex reflection optics for the one-dimensional enlargement of a 1 mm wide synchrotron beam by a factor of 5 to 10 within a 1 m distance. Four different optics are tested and characterized and their reflection properties compared to ray tracing simulations. The general shape and size of the measured reflection profiles agree with expectations. Enhancements with respect to homogeneity and efficiency can be expected with improved optics manufacturing. A mouse phantom is used for a proof-of-principle XFI experiment demonstrating the applicability of coarse and fine scans with the suggested optics design. 相似文献
12.
[Correction Notice: An erratum for this article was reported in Vol 15(3) of Group Dynamics: Theory, Research, and Practice (see record 2011-14268-001). An error was introduced during the production process. On article page 8, column 1 line 6 through column 2 line 2, the statement “…the main effect of expected longevity was significant only in the same expertise condition…” is incorrect. The effect found was for expected difficulty, not expected longevity.] The ability to effectively coordinate with others is a vital component of group success. It is often useful to base this coordination on expectations derived from perceived expertise (transactive memory; Wegner, 1986). Yet, the value of coordination overall and specific coordination strategies vary by task. We argue that the benefit of applying a task-appropriate coordination strategy increases with the number of trials of the task performed (expected longevity), and that the most beneficial strategy varies by task difficulty. We, therefore, predict that coordination increases with expected longevity and that the form of coordination (increased or decreased duplication) depends on expected task difficulty. To test these predictions we manipulate expectations of longevity and difficulty among individuals expecting to work with a partner on a memory task. The predicted relationships are found for both learning and recall. The implications of these findings for the development of transactive memory are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
13.
14.
Benzophenone Photoinduced Oxidation of Benzyl Aryl Ether and Aromatic Solvents α-Ether radicals formed in the photoreaction of benzophenone with benzyl phenyl ether were oxidized in benzene solution to phenol, benzaldehyde and phenylbenzoate. A mechanism including an instable intermediate α-ether hydroperoxide is discussed with the help of kinetic and CIDNP results. The quantum yields of the oxygen consumption show a linear dependence on the ether concentration. They are much higher in the pure solvent benzene than expected from the quenching and deactivation processes. This agrees with the existence of a biradicalic adduct of triplet benzophenone with aromatic solvents and shows that these solvents are far from being inert under these conditions. 相似文献
15.
H. Baumann H.-J. Timpe V. E. Zubarev N. V. Fok M. Y. Mel'nikov Y. W. Raskasovskij 《Advanced Synthesis \u0026amp; Catalysis》1985,327(5):749-758
Investigations on Spin-Trapping Kineties in Radical Systems with Different Reactivity. Photolyses of α-Phenylbenzoine in the Presence of Benzylideneter. -butylamine N-oxide As a model system to study the spin-trapping kinetics of systems forming two radicals of different reactivity α-phenylbenzoine (PhB) was chosen. The photolysis of PhB forms benzoyl (B·) and diphenylketylradikals (K·), respectively, which can be trapped by benzylidene-tert-butyl-amine N-oxide (PBN), as a spin trap. The rate constants of radical addition to PBN and their reactions with the spin adducts were determined by means of flash photolysis and kinetic calculations of the PBN concentration dependence. For B· and K· addtion rate constants to PBN of k1 = 8,1 × 105 M−1s−1, and k2 = 5,8 · 104 M−1s−1, respectively, were found. The rate constants for the reactions of B· and K· with the spin adducts are in the order of 109…1010 M−1s−1. 相似文献
16.
H. Baumann B. Strehmel H.-J. Timpe U. Lammel 《Advanced Synthesis \u0026amp; Catalysis》1984,326(3):415-425
Light Induced Polymer and Polymerization Reactions. 14. Radical Photopolymerization by Potassium Trisoxalato Cobaltate Arylonium Salts Systems. The photopolymerization of acrylamide (AA) by trisoxalato cobaltate ([Co(ox)3]3⊖) is inefficient because the produced nucleophilic ·CO2⊖-radicals are oxidized or they terminate with polymer radicals. If onium compounds are added to this system the initiation efficiency is increased as follows : p-CH3OC6H4N2⊕>Ph2I⊕>PhCOCH2S(CH3)2⊕>Ph3S⊕. By means of quantum yield measurements a mechanism was proposed including the electron transfer from ·CO2⊖ to onium compounds. The produced radicals also initiate the polymerization of AA. The exponent m of the polymerization rate (vp ≈︁ [AA]m) is decreased from 1.4 to 1.1 in the presence of Ph2I⊕, deciding the decrease of termination reaction between ·CO2⊖ and polymer radicals. In comparison with K3[Fx(ox)3] the corresponding cobalt complex possesses higher polymerization quantum yields for AA. 相似文献
17.
K. Gierschner und G. Baumann 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1969,139(3):132-141
Zusammenfassung Einleitend wird auf die Blausäure-enthaltenden (cyanogenen) Verbindungen besonders in den Rosaceen und Leguminosen eingegangen und auf die zunehmende Bedeutung der Verarbeitung von Prunoideen-Früchten — besonders von Sauerkirschen — zu Fruchtsäften und anderen Obsterzeugnissen hingewiesen. Dabei wird erwähnt, daß in diesen Erzeugnissen recht hohe Blausäuregehalte auftreten können. Andererseits wird hervorgehoben, daß Säfte und andere Produkte aus Prunoideen-Früchten durch Zugabe der entsprechenden zerkleinerten Steinsamen erheblich in ihrem Aroma verstärkt werden können und daß auch noch andere Möglichkeiten der Verarbeitung der Steine zwecks Gewinnung einer Reihe von wertvollen Produkten gegeben sind.Wegen der Giftigkeit der Blausäure wird auf die Notwendigkeit einer hinreichend genauen Erfassung der Blausäure in Prunoideen-Fruchterzeugnissen hingewiesen und die dazu bisher vorhandenen Methoden werden diskutiert. Besonders wird auf die grundlegende Arbeit vonHanssen u.Sturm (3), die sich mit der Isolierung der Blausäure besonders aus Mandeln befaßt, eingegangen. Diese Isollerungsmethode bewährte sich auch hier. Allerdings wurde anstelle der von diesen Autoren benutzten argentometrischen Bestimmung der Blausäure nach einer für unsere Zwecke erforderlichen empfindlicheren photometrischen Methode gesucht und eine solche gefunden. Nach dieser in Anlehnung anMurty u. Mitarb. (30) ausgearbeiteten Methode wird die Blausäure wie folgt bestimmt: HCN wird mit Brom zu Bromcyan und dieses mit Pyridin umgesetzt. Der beim Zerfall des vorherigen Reaktionsproduktes entstehende Glutaconaldehyd ergibt dann mit Barbitursäure einen Polymethinfarbstoff, dessen Extinktion bei 580 nm gemessen wird. Dieser Farbstoff, dessen anzunehmende Konstitution (31) im Schema 2 gebracht wird, erwies sich im Gegensatz zu einem mit Benzidin gebildeten ähnlichen Reaktionsprodukt als stabil und für die Messung gut geeignet.Mit der beschriebenen Methode wurden die Blausäuregehalte in Steinschrot sowie in selbst und industriell hergestellten Sauerkirschsäften untersucht und die Ergebnisse in einer Tabelle wiedergegeben. In einem der Handelssäfte wurde ein bedenklich hoher HCN-Gehalt gefunden.Schließlich wird mitgeteilt, daß mit zunehmendem Steinschrotanteil die Gefahr der Bildung von Äthanol in Kirschmaische entsprechend reduziert wird. Dieses Phänomen soll im Erntejahr 1968 weiter untersucht werden.I. Mitteilung: vgl. Literaturverzeichnis Nr. 10; IL Mitteilung: Nr. 11.FräuleinW. Haag danken wir herzlich für die gewissenhafte Durchführung der Analysen. 相似文献
18.
Dr. Roman J. Lichtenecker Dr. Bernhard Ellinger Dr. Hong‐Mei Han Kirtikumar B. Jadhav Dr. Sascha Baumann Dr. Oliwia Makarewicz Dr. Markus Grabenbauer Prof. Dr. Hans‐Dieter Arndt 《Chembiochem : a European journal of chemical biology》2013,14(18):2492-2499
Growing resistance to antibiotics, as well as newly emerging pathogens, stimulate the investigation of antimicrobial peptides (AMPs) as therapeutic agents. Here, we report a new library design concept based on a stochastic distribution of natural AMP amino acid sequences onto half‐length synthetic peptides. For these compounds, a non‐natural motif of alternating D ‐ and L ‐backbone stereochemistry of the peptide chain predisposed for β‐helix formation was explored. Synthetic D ‐/L ‐peptides with permuted half‐length sequences were delineated from a full‐length starter sequence and covalently recombined to create two‐dimensional compound arrays for antibacterial screening. Using the natural AMP magainin as a seed sequence, we identified and iteratively optimized hit compounds showing high antimicrobial activity against Gram‐positive and Gram‐negative bacteria with low hemolytic activity. Cryo‐electron microscopy characterized the membrane‐associated mechanism of action of the new D ‐/L ‐peptide antibiotics. 相似文献
19.
J. Meinen S. Khasminskaya E. Rühl W. Baumann T. Leisner 《Aerosol science and technology》2013,47(4):316-328
We present an experimental setup that allows the injection of charged nanoparticles in a diameter range of 3–15 nm into a vacuum chamber and their storage there in an electrodynamic cage. The nanoparticle density in the trap is limited by space charge and can be several orders of magnitude higher than in a free nanoparticle beam. The setup provides for the first time a tool for the application of advanced techniques of spectroscopy to free nanoparticles in this size range. It consists of a combination of (1) a plasma discharge nanoparticle source that generates a high density of nanoparticles of various composition suspended in helium carrier gas at a pressure of about 10–150 mbar, (2) an aerodynamic lens optimized for small particles (diameter 3–15 nm) that forms a well-collimated beam of charged nanoparticles and focuses it into (3) an octopole ion trap operated at low frequencies and filled with helium buffer gas at 10?2 mbar in order to moderate and store the nanoparticles at densities of more than 107 cm?3. 相似文献
20.
Y. Xing S. Baumann S. Uhlenbruck M. Rüttinger A. Venskutonis W.A. Meulenberg D. Stöver 《Journal of the European Ceramic Society》2013,33(2):287-296
Asymmetric perovskite membranes have an attractive potential in the application of O2/N2 gas separation for future membrane-based power plants using oxyfuel technology. In this study – a metal-supported membrane structure with a thin-film perovskite layer and porous ceramic interlayers was developed. Porous NiCoCrAlY sintered at 1225 °C in H2 was selected as the substrate based on a sufficient permeability and corrosion resistance in co-firing conditions. According to the oxidation behaviour of NiCoCrAlY, the temperature for co-firing of the substrate and the interlayers was defined as 1100 °C for 5 h in air. Two interlayers of La0.58Sr0.4Co0.2Fe0.8O3?δ were applied by screen printing. The top layer was deposited by magnetron sputtering with a thickness of 3.8 μm. While gas-tightness was improved considerably, significant air-leakage was still detected. In summary, the successful development of a metal-perovskite-composite is shown, which acts as a basis for further development of a gas-tight metal-supported oxygen transport membrane structure. 相似文献