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91.
92.
G. Roebben S. Ramirez-Garcia V. A. Hackley M. Roesslein F. Klaessig V. Kestens I. Lynch C. M. Garner A. Rawle A. Elder V. L. Colvin W. Kreyling H. F. Krug Z. A. Lewicka S. McNeil A. Nel A. Patri P. Wick M. Wiesner T. Xia G. Oberd?rster K. A. Dawson 《Journal of nanoparticle research》2011,13(7):2675-2687
The International Alliance for NanoEHS Harmonization (IANH) organises interlaboratory comparisons of methods used to study the potential biological impacts of nanomaterials. The aim of IANH is to identify and reduce or remove sources of variability and irreproducibility in existing protocols. Here, we present results of the first IANH round robin studies into methods to assess the size and surface charge of suspended nanoparticles. The test materials used (suspensions of gold, silica, polystyrene, and ceria nanoparticles, with [primary] particles sizes between 10?nm and 80?nm) were first analysed in repeatability conditions to assess the possible contribution of between-sample heterogeneity to the between-laboratory variability. Reproducibility of the selected methods was investigated in an interlaboratory comparison between ten different laboratories in the USA and Europe. Robust statistical analysis was used to evaluate within- and between-laboratory variability. It is shown that, if detailed shipping, measurement, and reporting protocols are followed, measurement of the hydrodynamic particle diameter of nanoparticles in predispersed monomodal suspensions using the dynamic light scattering method is reproducible. On the other hand, measurements of more polydisperse suspensions of nanoparticle aggregates or agglomerates were not reproducible between laboratories. Ultrasonication, which is commonly used to prepare dispersions before cell exposures, was observed to further increase variability. The variability of the zeta potential values, which were also measured, indicates the need to define better surface charge test protocols and to identify sources of variability. 相似文献
93.
R. M. Eremina T. P. Gavrilova A. Günther Z. Wang R. Lortz M. Johnsson H. Berger H. A. Krug von Nidda J. Deisenhofer A. Loidl 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,84(3):391-395
We report on magnetization and specific heat measurements on single-crystalline
CuTe2O5. The experimental data are directly compared to
theoretical results for two different spin structures, namely an alternating spin-chain
and a two-dimensional (2D) coupled dimer model, obtained by Das et al. [Phys. Rev. B
77, 224437 (2008)]. While the analysis of the specific heat does not allow
to distinguish between the two models, the magnetization data is in good agreement with
the 2D coupled dimer model. 相似文献
94.
We study the evolution of a population in a two-locus genotype space, in which the negative effects of two single mutations are overcompensated in a high-fitness double mutant. We discuss how the interplay of finite population size N and sexual recombination at rate r affects the escape times t(esc) to the double mutant. For small populations demographic noise generates massive fluctuations in t(esc). The mean escape time varies nonmonotonically with r, and grows exponentially as lnt(esc)~N(r-r(*))(3/2) beyond a critical value r(*). 相似文献
95.
We study biological evolution in a high-dimensional genotype space in the regime of rare mutations and strong selection. The population performs an uphill walk which terminates at local fitness maxima. Assigning fitness randomly to genotypes, we show that the mean walk length is logarithmic in the number of initially available beneficial mutations, with a prefactor determined by the tail of the fitness distribution. This result is derived analytically in a simplified setting where the mutational neighborhood is fixed during the adaptive process, and confirmed by numerical simulations. 相似文献
96.
Park JT Friemel G Li Y Kim JH Tsurkan V Deisenhofer J Krug von Nidda HA Loidl A Ivanov A Keimer B Inosov DS 《Physical review letters》2011,107(17):177005
We have studied the low-energy spin-excitation spectrum of the single-crystalline Rb(2)Fe(4)Se(5) superconductor (T(c)=32 K) by means of inelastic neutron scattering. In the superconducting state, we observe a magnetic resonant mode centered at an energy of ?ω(res)=14 meV and at the (0.5 0.25 0.5) wave vector (unfolded Fe-sublattice notation), which differs from the ones characterizing magnetic resonant modes in other iron-based superconductors. Our finding suggests that the 245-iron selenides are unconventional superconductors with a sign-changing order parameter, in which bulk superconductivity coexists with the √5×√5 magnetic superstructure. The estimated ratios of ?ω(res)/k(B)T(c)≈5.1±0.4 and ?ω(res)/2Δ≈0.7±0.1, where Δ is the superconducting gap, indicate moderate pairing strength in this compound, similar to that in optimally doped 1111 and 122 pnictides. 相似文献
97.
J. H. Jocum B. Weiss Franz Cerych Von Schroeder A. Bartel und H. Krug 《Fresenius' Journal of Analytical Chemistry》1896,35(1):601-606
Ohne Zusammenfassung 相似文献
98.
H. Borchers C. Tammann B. Kerl C. Krug C. Schiffner und F. Michel 《Fresenius' Journal of Analytical Chemistry》1933,91(5-6):213-214
Ohne Zusammenfassung 相似文献
99.
100.
C. von der Heide H. Straube W. Seifert J. Mayrhofer G. Jörgensen O. Krug und I. Rettinger 《Fresenius' Journal of Analytical Chemistry》1925,66(6):250-254
Ohne Zusammenfassung 相似文献