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61.
Alicja Boryło Bogdan Skwarzec Grzegorz Romańczyk Janusz Siebert 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(3):1685-1691
The determination of polonium 210Po in human blood samples is presented and discussed in this paper. The human blood samples were collected from patients of Medical University of Gdańsk with ischaemic heart disease (morbus ischaemicus cordis, MIC). The polonium concentrations in analyzed human blood samples are very differentiated. 210Po is of particular interest in public health and although is present in the environment in extremely low amounts, it is easily bioaccumulated to the human body. The study shows that the amount of 210Po that is incorporated into the human body depends on the food habits and some difference in its levels could be observed between smokers and non-smokers. 相似文献
62.
Roman Tkachov Lukas Stepien Aljoscha Roch Hartmut Komber Felix Hennersdorf Jan J. Weigand Ingmar Bauer Anton Kiriy Christoph Leyens 《Tetrahedron》2017,73(16):2250-2254
Herein, aiming at optimization of the polymerization process leading to a family of hole- and electron-conducting 1,1,2,2-ethenetetrathiolate-based polymers, such as poly(nickel-1,1,2,2-ethenetetrathiolate), poly[Kx(Ni-ett)], we investigated transformations of the monomer precursor 1,3,4,6-tetrathiapentalene-2,5-dione (TPD) occurring under polymerization conditions. We found that only one ring of TPD opens upon its reaction with potassium methoxide under inert conditions at room temperature which leads to the formation of potassium 2-oxo-1,3-dithiol-4,5-dithiolate (K2[3]). Heating of K2[3] under reflux in methanol solution under inert conditions opens the second ring, however the resulting product is not potassium ethenetetrathiolate (K4[2]), the product of an exhaustive methanolysis of TPD, but potassium tetrathiooxalate (K2[4]), the product of the decarbonylation of K2[3]. Preliminary experiments reveal that the involvement of K2[4] in the polymerization process is beneficial for reproducible formation of high quality 1,1,2,2-ethenetetrathiolate-based polymers suitable for thermoelectric applications. 相似文献
63.
Nikolaus M. Loening Barth‐Jan van Rossum Hartmut Oschkinat 《Magnetic resonance in chemistry : MRC》2012,50(4):284-288
In nuclear magnetic resonance spectroscopy, experimental limits due to the radiofrequency transmitter and/or coil means that conventional radiofrequency pulses (“hard pulses”) are sometimes not sufficiently powerful to excite magnetization uniformly over a desired range of frequencies. Effects due to nonuniform excitation are most frequently encountered at high magnetic fields for nuclei with a large range of chemical shifts. Using optimal control theory, we have designed broadband excitation pulses that are suitable for solid‐state samples under magic‐angle‐spinning conditions. These pulses are easy to implement, robust to spinning frequency variations, and radiofrequency inhomogeneities, and only four times as long as a corresponding hard pulse. The utility of these pulses for uniformly exciting 13C nuclei is demonstrated on a 900 MHz (21.1 T) spectrometer. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
64.
Joerg Max Siebert Grit Baier Katharina Landfester 《Journal of polymer science. Part A, Polymer chemistry》2012,50(1):80-88
A new class of polyurethanes has been designed, containing tertiary carbamate groups in the main chain of the polymer, which enable the resulting polymer to degrade completely under acid and thermal treatment. The decomposition temperatures of the polymers were determined by measuring the evolution of carbon dioxide and other decomposition products using TGA‐MS. Until decomposition of the polymer, no glass transition was found. The polymers exhibit excellent solubility in common organic solvents like chloroform and tetrahydrofuran, making them to suitable materials for film formation. From the obtained polymers, nanoparticles were synthesized by the solvent evaporation method combined with the miniemulsion technique. The resulting nanoparticles can be used as intelligent fillers in films and sensors, since they degrade at temperatures of above 180 °C, which can be detected by a color change reaction with ninhydrin. Polymeric nanocapsules were prepared by an interfacial polyaddition reaction from 2,4‐toluene diisocyanate and tertiary diols performed at the droplet's interface in inverse (water‐in‐oil) miniemulsions. These nanocapsules with an encapsulated photoacid generator can act as a release system, whereby an acidic release through irradiation with ultraviolet light can be triggered. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
65.
Mahmoud Nasrollahzadeh Mohaddeseh Sajjadi Hartmut Komber Hossein Ali Khonakdar S. Mohammad Sajadi 《应用有机金属化学》2019,33(7)
In the present work, for the first time we have designed a novel approach for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles using reduced graphene oxide (rGO) decorated with Cu‐Ni bimetallic nanoparticles (NPs). In situ synthesis of Cu/Ni/rGO nanocomposite was performed by a cost efficient, surfactant‐free and environmentally benign method using Crataegus azarolus var. aronia L. leaf extract as a stabilizing and reducing agent. Phytochemicals present in the extract can be used to reduce Cu2+ and Ni2+ ions and GO to Cu NPs, Ni NPs and rGO, respectively. Analyses by means of FT‐IR, UV–Vis, EDS, TEM, FESEM, XRD and elemental mapping confirmed the Cu/Ni/rGO formation and also FT‐IR, NMR, and mass spectroscopy as well as elemental analysis were used to characterize the tetrazoles. The Cu/Ni/rGO nanocomposite showed the superior catalytic activity for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles within a short reaction time and high yields. Furthermore, this protocol eliminates the need to handle HN3. 相似文献
66.
Gerhard Gompper Clemens Bechinger Stephan Herminghaus Rolf Isele-Holder U. Benjamin Kaupp Hartmut Löwen Holger Stark Roland G. Winkler 《The European physical journal. Special topics》2016,225(11-12):2061-2064
Locomotion of autonomous microswimmers is a fascinating field at the cutting edge of science. It combines the biophysics of self-propulsion via motor proteins, artificial propulsion mechanisms, swimming strategies at low Reynolds numbers, the hydrodynamic interaction of swimmers, and the collective motion and synchronisation of large numbers of agents. The articles of this Special Issue are based on the lecture notes of an international summer school, which was organized by the DFG Priority Programme 1726 “Microswimmers – From Single Particle Motion to Collective Behaviour” in the fall of 2015. The minireviews provide a broad overview of the field, covering both elementary and advanced material, as well as selected areas from current research. 相似文献
67.
Carbon,nitrogen and sulphur isotopic fractionation in captive juvenile hooded seal (Cystophora cristata): Application for diet analysis
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68.
Hartmut B. Stegmann Hansjörg V. Dumm Klaus Scheffler 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):159-170
Abstract Pentakoordinierte Phosphorverbindungen vom Typ der 2.3-Dihydro-1.3.2-benzoxazaphosphole entstehen bei der Umsetzung von 2-Amino-phenolen oder N-Äthyl-2-hydroxy-anilinen mit Diphenyl-trifluorphosphoran unter Verwendung von Triäthylamin als Fluorwasserstoff-Akzeptor. Die Synthese einer großen Anzahl verschieden substituierter Spezies zeigt die Allgemeingültigkeit dieses Verfahrens. Die isolierbaren Substanzen werden durch NMR-Spektren (1H, 31P, 19F) und die üblichen analytischen Methoden charakterisiert. Die Markierung einer Verbindung mit 15N trägt wesentlich zur Struktursicherung bei. Bei den 3-H-2-Fluor-2.2-diphenyl-1.3.2-benzoxazaphospholen wurde ein bemerkenswerter Zusammenhang zwischen P–F-Kopplungskonstante und dem F-shift aufgefunden, der eine lineare Korrelation dieser beiden Größen erkennen läßt. Pentacoordinated phosphorus compounds of the type of 2,3-dihydro-1,3,2-benzoxazaphospholes originate from reaction of 2-aminophenol or N-ethyl-2-hydroxyaniline with diphenyl-trifluorophosphorane using triethylamine as an HF-acceptor. The described synthesis of a great number of differently substituted species indicates the wide field of application. The substances are characterized by nmr spectroscopy (1H, 31P, 19F) and the usual analytical methods. By marking one compound with 15N the structure assignment is proved. Remarkably, the compounds of the type 3-H-2-fluoro-2,2-diphenyl-1,3,2-benzoxazaphospholes exhibit a nearly linear correlation between the P–F-coupling constants and the F-chemical shift. 相似文献
69.
Oliver Brücher Uwe Bergsträßer Harald Kelm Jens Hartung Marco Greb Ingrid Svoboda Hartmut Fuess 《Tetrahedron》2012,68(34):6968-6980
A cascade, composed of (i) oxovanadium(V)-catalyzed oxidation of bromide by tert-butyl hydroperoxide and (ii) stereoselective 6-endo-bromocyclization, affords 3-bromo-2-aryl-2,6,6-trimethyltetrahydropyrans from styrene-type tertiary alkenols in synthetically useful yields. (E)-Alkenols add the bromo- and the alkoxy substituent anti-selectively across the double bond, indicating a bromonium ion-mechanism for the ring closure. 6-endo-control of the alkenol cyclization thereby arises from the polar effect of the aryl substituent. Two methyl substituents bound to the alkene terminus are not similarly able to favor 6-endo-cyclization, because strain arising from methyl group repulsion, as the bromonium-activated π-bond and the hydroxyl oxygen approach, directs bromocyclization of tertiary prenyl-type substrates toward tetrahydrofuran formation. A hexasubstituted bromotetrahydropyran prepared from the oxidation/bromocyclization cascade served as starting material for synthesis of racemic aplysiapyranoid A, in a sequence of free radical and polar functional group interconversion. 相似文献
70.