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991.
Ralf Warratz Dr. Hanane Aboulfadl Thomas Bally Prof. Felix Tuczek Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(7):1604-1617
New transitions : Low‐energy electronic transitions have been detected spectroscopically in the FeII–FeIII mixed‐valent biferrocenyl radical cation, but are absent in the spectra of the neutral analogue. They have been assigned by time‐dependent DFT calculations (squares in figure). Analogous investigations were performed for the bisfulvalenide FeII–FeIII radical cation.
992.
Andreas Keilbach Markus Döblinger Dr. Ralf Köhn Dr. Heinz Amenitsch Dr. Thomas Bein Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(27):6645-6650
Confined tubes : Periodic mesoporous organosilica (PMO) mesophases were synthesized within the confined tubular environment of anodic alumina membrane (AAM) channels, resulting in the formation of either the hexagonal circular or the cubic mesophase.
993.
Ralf Bienert Franziska Emmerling Andreas F. Thünemann 《Analytical and bioanalytical chemistry》2009,395(6):1651-1660
The spherical gold nanoparticle reference materials RM 8011, RM 8012, and RM 8013, with a nominal radius of 5, 15, and 30 nm,
respectively, have been available since 2008 from NIST. These materials are recommended as standards for nanoparticle size
measurements and for the study of the biological effects of nanoparticles, e.g., in pre-clinical biomedical research. We report
on determination of the size distributions of these gold nanoparticles using different small-angle X-ray scattering (SAXS)
instruments. Measurements with a classical Kratky type SAXS instrument are compared with a synchrotron SAXS technique. Samples
were investigated in situ, positioned in capillaries and in levitated droplets. The number-weighted size distributions were
determined applying model scattering functions based on (a) Gaussian, (b) log-normal, and (c) Schulz distributions. The mean
radii are 4.36 ± 0.04 nm (RM 8011), 12.20 ± 0.03 nm (RM 8012), and 25.74 ± 0.27 nm (RM 8013). Low polydispersities, defined
as relative width of the distributions, were detected with values of 0.067 ± 0.006 (RM 8011), 0.103 ± 0.003, (RM 8012), and
0.10 ± 0.01 (RM 8013). The results are in agreement with integral values determined from classical evaluation procedures,
such as the radius of gyration (Guinier) and particle volume (Kratky). No indications of particle aggregation and particle
interactions—repulsive or attractive—were found. We recommend SAXS as a standard method for a fast and precise determination
of size distributions of nanoparticles.
相似文献
994.
We study the module category of a certain Galois covering of a cluster-tilted algebra which we call the cluster repetitive algebra. Our main result compares the module categories of the cluster repetitive algebra of a tilted algebra C and the repetitive algebra of C, in the sense of Hughes and Waschbüsch. 相似文献
995.
Shengli Guo Ralf Hauptmann Serena Losi Piero Zanello Jörg J. Schneider 《Journal of organometallic chemistry》2009,694(7-8):1022-1026
The title compounds 3 and 4 were synthesized by reaction of 1,1′ ferrocenylenediol with the Co triple decker compounds [{(η5-Me5C5)Co}2(η6:η6-toluene)] and [{(η5-EtMe4C5)Co}2(η6:η6-toluene)], respectively. The central Co atom of 3 is coordinated by five O atoms in a square-pyramidal manner. The remaining two Co atoms of 3 are coordinated to a Me5C5 ligand in a η5-fashion and by the two O atoms of two 1,1′ ferrocenylenediolato ligands which serve as chelating ligands. In 4, the central Co atom is coordinated to all six O atoms of three ferrocenylenediolato ligands in a trigonal-prismatic manner, whereas the two other Co atoms are coordinated by an EtMe4C5 ligand in a η5-fashion and by three O atoms of three ferrocenylenediolato ligands resulting in an overall tripoidal structure for 4. 相似文献
996.
997.
We present a theoretical framework for the thermodynamic properties of supercoiling-induced denaturation bubbles in circular double-stranded DNA molecules. We explore how DNA supercoiling, ambient salt concentration, and sequence heterogeneity impact on the bubble occurrence. An analytical derivation of the probability distribution to find multiple bubbles is derived and the relevance for supercoiled DNA discussed. We show that in?vivo sustained DNA bubbles are likely to occur due to partial twist release in regions rich in weaker AT base pairs. Single DNA plasmid imaging experiments clearly demonstrate the existence of bubbles in free solution. 相似文献
998.
We calculate the radiation resulting from the Unruh effect for strongly accelerated electrons and show that the photons are created in pairs whose polarizations are perfectly correlated. Apart from the photon statistics, this quantum radiation can further be discriminated from the classical (Larmor) radiation via the different spectral and angular distributions. The signatures of the Unruh effect become significant if the external electromagnetic field accelerating the electrons is not too far below the Schwinger limit and might be observable with future facilities. Finally, the corrections due to the birefringent nature of the QED vacuum at such ultrahigh fields are discussed. 相似文献
999.
Benjamin Gesemann Stefan L. Schweizer Ralf B. Wehrspohn 《Photonics and Nanostructures》2010,8(2):107-111
We present measurements of the thermal emission properties of 2D and 3D silicon photonic crystals with and without substrate heated resistively as well as passively with an aluminium hotplate. The out-of-plane and in-plane emission properties were recorded and compared to numerical simulation. It turned out that for the in-plane 2D photonic crystal and out-of-plane 3D photonic crystal emission a photonic stop gap effect is visible. For the out-of-plane 2D photonic crystal emission, no photonic bandgap effect is observable but instead strong silicon oxide emission from native oxide inside the pores of silicon are observable. A model for the modified thermal emission is presented. 相似文献
1000.