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111.
Vincent Moxley-Paquette Bing Wu Daniel Lane Monica Bastawrous Paris Ning Ronald Soong Peter De Castro Ivan Kovacevic Thomas Frei Juerg Stuessi Danijela Al Adwan-Stojilkovic Stephan Graf Franck Vincent Daniel Schmidig Till Kuehn Rainer Kuemmerle Armin Beck Michael Fey Wolfgang Bermel Falko Busse Marcel Gundy Holger Boenisch Hermann Heumann Ben Nashman Rudraksha Dutta Majumdar Andressa Lacerda André J. Simpson 《Magnetic resonance in chemistry : MRC》2022,60(3):386-397
Microcoils provide a cost-effective approach to improve detection limits for mass-limited samples. Single-sided planar microcoils are advantageous in comparison to volume coils, in that the sample can simply be placed on top. However, the considerable drawback is that the RF field that is produced by the coil decreases with distance from the coil surface, which potentially limits more complex multi-pulse NMR pulse sequences. Unfortunately, 1H NMR alone is not very informative for intact biological samples due to line broadening caused by magnetic susceptibility distortions, and 1H-13C 2D NMR correlations are required to provide the additional spectral dispersion for metabolic assignments in vivo or in situ. To our knowledge, double-tuned single-sided microcoils have not been applied for the 2D 1H-13C analysis of intact 13C enriched biological samples. Questions include the following: Can 1H-13C 2D NMR be performed on single-sided planar microcoils? If so, do they still hold sensitivity advantages over conventional 5 mm NMR technology for mass limited samples? Here, 2D 1H-13C HSQC, HMQC, and HETCOR variants were compared and then applied to 13C enriched broccoli seeds and Daphnia magna (water fleas). Compared to 5 mm NMR probes, the microcoils showed a sixfold improvement in mass sensitivity (albeit only for a small localized region) and allowed for the identification of metabolites in a single intact D. magna for the first time. Single-sided planar microcoils show practical benefit for 1H-13C NMR of intact biological samples, if localized information within ~0.7 mm of the 1 mm I.D. planar microcoil surface is of specific interest. 相似文献
112.
Verena M. Weiss Toufik Naolou Elkin Amado Karsten Busse Karsten Mder Jrg Kressler 《Macromolecular rapid communications》2012,33(1):35-40
A simple approach using comb‐like polymers that undergo nanophase separation between the polyester backbone and the stearoyl side chains is proposed for the preparation of structured non‐spherical nanoparticles from a nanoemulsion. Depending on the degree of esterification of the OH groups of poly(glycerol adipate) differently ordered nanostructures is obtained. A perfect lamellar arrangement is obtained for polymers with a high degree of esterification and leads to spherical nanoparticles with an internal onion‐like structure. However, when the degree of esterification is only 20 mol%, polygonal nanoparticles with an internal pseudo‐hexagonal structure are obtained. The differences in the nanoparticle shapes are related to the volume fraction of the paraffinic pool. 相似文献
113.
We study the structure and stability of the first water layer on Pt(111) by variable-temperature scanning tunneling microscopy. We find that a high Pt step edge density considerably increases the long-range order of the equilibrium √37 × √37R25.3°- and √39 × √39R16.1°-superstructures, presumably due to the capability of step edges to trap residual adsorbates from the surface. Passivating the step edges with CO or preparing a flat metal surface leads to the formation of disordered structures, which still show the same structural elements as the ordered ones. Coadsorption of Xe and CO proves that the water layer covers the metal surface completely. Moreover, we determine the two-dimensional crystal structure of Xe on top of the chemisorbed water layer which exhibits an Xe-Xe distance close to the one in bulk Xe and a rotation angle of 90° between the close-packed directions of Xe and the close-packed directions of the underlying water layer. CO is shown to replace H(2)O on the Pt(111) surface as has been deduced previously. In addition, we demonstrate that tunneling of electrons into the antibonding state or from the bonding state of H(2)O leads to dissociation of the molecules and a corresponding reordering of the adlayer into a √3 × √3R30°-structure. Finally, a so far not understood restructuring of the adlayer by an increased tunneling current has been observed. 相似文献
114.
Purpose
To determine whether a greatly reduced spatial resolution of fully reconstructed projection MR images can be used for the simultaneous 3D localization of multiple MR-visible markers and to assess the feasibility of a subsecond position tracking for clinical purposes.Materials and Methods
Miniature, inductively coupled RF coils were imaged in three orthogonal planes with a balanced steady-state free precession (SSFP) sequence and automatically localized using a two-dimensional template fitting and a subsequent three-dimensional (3D) matching of the coordinates. Precision, accuracy, speed and robustness of 3D localization were assessed for decreasing in-plane resolutions (0.6–4.7 mm). The feasibility of marker tracking was evaluated at the lowest resolution by following a robotically driven needle on a complex 3D trajectory.Results
Average 3D precision and accuracy, sensitivity and specificity of localization ranged between 0.1 and 0.4 mm, 0.5 and 1.0 mm, 100% and 95%, and 100% and 96%, respectively. At the lowest resolution, imaging and localization took ≈350 ms and provided an accuracy of ≈1.0 mm. In the tracking experiment, the needle was clearly depicted on the oblique scan planes defined by the markers.Conclusion
Image-based marker localization at a greatly reduced spatial resolution is considered a feasible approach to monitor reference points or rigid instruments at subsecond update rates. 相似文献115.
116.
117.
N. Bijnens I. Ahmad A. N. Andreyev J. C. Batchelder C. R. Bingham D. Blumenthal B. C. Busse X. S. Chen L. F. Conticchio C. N. Davids M. Huyse R. V. F. Janssens P. Mantica H. Penttila W. Reviol D. Seweryniak P. Van Duppen W. B. Walters J. Wauters B. E. Zimmerman 《Zeitschrift für Physik A Hadrons and Nuclei》1996,354(1):3-4
The production of energetic π? at 0° has been measured in Ne+NaF and Ni+Ni collisions with incident energies between 1.3 and 2AGeV. In Ne+NaF collisions the investigation was extended to extreme subthreshold processes with lab momenta up to 4.5 GeV/c. In both systems at all incident energies the π? production cross sections deviate in a systematic way from thermal distributions. 相似文献
118.
119.
Alexandra Inayat Ayman Makky Jose Giraldo Andreas Kuhnt Corinna Busse Prof. Dr. Wilhelm Schwieger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):8161-8169
An in situ method for the growth of ZnO nanocrystals on Zn/Al mixed metal oxide (MMO) surfaces is presented. The key to this method is the thermal treatment of Zn/Al layered double hydroxides (Zn/Al LDHs) in the presence of nitrate anions, which results in partial demixing of the LDH/MMO structure and the subsequent crystallization of ZnO crystals on the surface of the forming MMO layers. In a first experimental series, thermal treatment of Zn/Al LDHs with different fractions of nitrate and carbonate in the interlayer space was examined by thermogravimetry coupled with mass spectrometry (TG‐MS) and in situ XRD. In a second experimental series, Zn/Al LDHs with only carbonate in the interlayer space were thermally treated in the presence of different amounts of an external nitrate source (NH4NO3). All obtained Zn/Al MMO samples were analysed by electron microscopy, nitrogen physisorption and powder X‐ray diffraction. The gas phase formed during nitrate decomposition turned out to be responsible for the formation of crystalline ZnO nanoparticles. Accordingly, both interlayer nitrate and the presence of ammonium nitrate led to the formation of supported ZnO nanocrystals with mean diameters between 100 and 400 nm, and both methods offer the possibility to tailor the amount and size of the ZnO crystals by means of the amount of nitrate. 相似文献
120.
Haozhe Yang Simone Budow‐Busse Henning Eickmeier Hans Reuter Frank Seela 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(12):1116-1120
The title compound {systematic name: 4‐amino‐5‐cyclopropyl‐7‐(2‐deoxy‐β‐D‐erythro‐pentofuranosyl)‐7H‐pyrrolo[2,3‐d]pyrimidine}, C14H18N4O3, exhibits an anti glycosylic bond conformation, with the torsion angle χ = −108.7 (2)°. The furanose group shows a twisted C1′‐exo sugar pucker (S‐type), with P = 120.0 (2)° and τm = 40.4 (1)°. The orientation of the exocyclic C4′—C5′ bond is ‐ap (trans), with the torsion angle γ = −167.1 (2)°. The cyclopropyl substituent points away from the nucleobase (anti orientation). Within the three‐dimensional extended crystal structure, the individual molecules are stacked and arranged into layers, which are highly ordered and stabilized by hydrogen bonding. The O atom of the exocyclic 5′‐hydroxy group of the sugar residue acts as an acceptor, forming a bifurcated hydrogen bond to the amino groups of two different neighbouring molecules. By this means, four neighbouring molecules form a rhomboidal arrangement of two bifurcated hydrogen bonds involving two amino groups and two O5′ atoms of the sugar residues. 相似文献