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51.
The strain amplitude dependence of the viscoelastic properties of eight different carbon blacks dispersed in two different rubbery networks is investigated and evaluated within the Cole-Cole approach for the complex elastic modulus at fixed temperature and frequency. This approach is based on the Kraus model of strain-dependent filler agglomeration-deagglomeration rates. We find a non-integer universal shape exponent of the Cole-Cole process that obviously depends only on the surrounding polymer matrix but is independent of the filler grade. The exponent can be related to the fractal dimension of the carbon black surface. 相似文献
52.
Carla Kirschbaum Essa M. Saied Kim Greis Eike Mucha Sandy Gewinner Wieland Schllkopf Gerard Meijer Gert von Helden Berwyck L. J. Poad Stephen J. Blanksby Christoph Arenz Kevin Pagel 《Angewandte Chemie (International ed. in English)》2020,59(32):13638-13642
1‐Deoxysphingolipids are a recently described class of sphingolipids that have been shown to be associated with several disease states including diabetic and hereditary neuropathy. The identification and characterization of 1‐deoxysphingolipids and their metabolites is therefore highly important. However, exact structure determination requires a combination of sophisticated analytical techniques due to the presence of various isomers, such as ketone/alkenol isomers, carbon–carbon double‐bond (C=C) isomers and hydroxylation regioisomers. Here we demonstrate that cryogenic gas‐phase infrared (IR) spectroscopy of ionized 1‐deoxysphingolipids enables the identification and differentiation of isomers by their unique spectroscopic fingerprints. In particular, C=C bond positions and stereochemical configurations can be distinguished by specific interactions between the charged amine and the double bond. The results demonstrate the power of gas‐phase IR spectroscopy to overcome the challenge of isomer resolution in conventional mass spectrometry and pave the way for deeper analysis of the lipidome. 相似文献
53.
Ana Isabel González Flórez Eike Mucha Dr. Doo‐Sik Ahn Sandy Gewinner Dr. Wieland Schöllkopf Prof. Dr. Kevin Pagel Dr. Gert von Helden 《Angewandte Chemie (International ed. in English)》2016,55(10):3295-3299
Here we present a combined experimental and theoretical study on the secondary structure of isolated proteins as a function of charge state. In infrared spectra of the proteins ubiquitin and cytochrome c, amide I (C=O stretch) and amide II (N–H bend) bands can be found at positions that are typical for condensed‐phase proteins. For high charge states a new band appears, substantially red‐shifted from the amide II band observed at lower charge states. The observations are interpreted in terms of Coulomb‐driven transitions in secondary structures from mostly helical to extended C5‐type hydrogen‐bonded structures. Support for this interpretation comes from simple energy considerations as well as from quantum chemical calculations on model peptides. This transition in secondary structure is most likely universal for isolated proteins that occur in mass spectrometric experiments. 相似文献
54.
Photoactivation of silver-exchanged zeolite A 总被引:1,自引:0,他引:1
55.
Francis R. Costa Sudip Pradhan Udo Wagenknecht Anil K. Bhowmick Gert Heinrich 《Journal of Polymer Science.Polymer Physics》2010,48(22):2302-2311
In elastomer/organo clay nanocomposites, the morphological characteristics, and hence the mechanical properties, of the vulcanizates are strongly influenced by the organic modifier and the vulcanization process. When the elastomer itself undergoes strain‐induced crystallization, both the organic modifier and the dispersed filler particles could significantly influence the crystallization process. These phenomena are very common in case of natural rubber‐based vulcanizates. In this study, the similar effects have been demonstrated with carboxylated nitrile rubber (XNBR) and organically modified layered double hydroxide (O‐LDH)‐based nanocomposites. The effect of size of the organic modifier was obviously visible on the interlayer distance of O‐LDH and also on the morphological reorganization of the dispersed O‐LDH particles during vulcanization process. The strain‐induced crystallization of the XNBR was found to be strongly dependent on the morphological change that occurs during vulcanization process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010 相似文献
56.
The purity P of laboratory chemicals is often declared in the form P > or = xy% (e.g., P > or = 97%). With a randomly chosen set of 40 compounds we found that their purity is generally closer to 100% than to the lower limit. The distribution of the purity data as found in the laboratory depends on the analytical technique used. Whereas purities determined by chromatography do not exceed 100% (because the sum of all observed peak areas is set to 100%), the purities obtained by titration can exceed 100% (because the functionality of the compound is measured). Therefore, the data for these two groups need to be dealt with in different ways. For purities based on titration we propose to use a rectangular distribution with a range from Pmin to 101%, an expected purity value which is the mean and a standard uncertainty of the purity u(P) of 29% of the range. Purities determined by chromatography can be described with a triangular distribution (ramp function). One leg of the triangle represents the range from Pmin to 100% and the right-angle is located at 100%. The expected value is the median and the uncertainty u(P) is 24% of the range. These proposals match the experimental data well. 相似文献
57.
Expression patterns of antioxidant proteins in brains of patients with sporadic Creutzfeldt-Jacob disease 总被引:5,自引:0,他引:5
Using two-dimensional gel electrophoresis (2-DE) and Western blot analysis, we were able to identify and quantify six antioxidant proteins, peroxiredoxin (Prx) I, Prx II, Prx III, 1-Cys Prx, putative peroxisomal antioxidant enzyme (PLP), and mitochondrial Mn superoxide dismutase (Mn-SOD) in two individual brain regions, cerebellum and frontal cortex of patients with sporadic Creutzfeldt-Jacob (sCJD). Among six antioxidant proteins, 1-Cys Prx showed significant increase (P > 0.05) in sCJD frontal cortex whereas Prx I was decreased (P > 0.01). In cerebellum, levels of all antioxidant proteins studied were comparable to those of controls. Our findings provide evidence for the link between aberrant expression of antioxidant proteins, 1-Cys Prx and Prx I and CJD neuropathogenesis and we discuss the neuropathological meaning of these dysregulated antioxidant proteins in sCJD brain. 相似文献
58.
A variety of jumps has in the past been identified in diffusion of atoms on 1D channeled surfaces. To establish the jump processes important in diffusion on a 2D surface, the movement of individual Pd atoms has been examined on W(110). From the distribution of displacements of Pd at high temperatures, double jumps are found along the close-packed <111>. For the first time, sizable differences are also observed between the mean-square displacements along x and y, which demonstrate unexpected contributions from jumps along <110>, but not along <001>. These jumps proceed over activation barriers higher than for single jumps, under conditions predicted from previous work with Pd on the channeled W(211). 相似文献
59.
Niobium and tantalum carbide clusters have been isolated in the gas phase and irradiated with intense tunable infrared (IR) light. Stable neutral clusters are selectively ionized and subsequently detected in a mass spectrometer. By tuning the IR frequency, infrared multiphoton absorption spectra are obtained for a whole range of clusters. These mass-selective IR spectra lead to insights into the structures of small niobium and tantalum carbide clusters and nanocrystals. 相似文献
60.
Gert Due Billing 《Chemical physics》1983,74(2):143-152
By using a semiclassical approach we derive an effective potential which governs the motion of the colliding atom/molecule. The effective potential depends on the surface temperature and the phonon excitation during the collision. Numerical results on Ar + W(110) are discussed and compared with experimental data. 相似文献