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71.
The structure and deformation behaviour of a new class of thermoplastic elastomers is studied by temperature dependent infrared (IR) spectroscopy and by IR - dichroism spectroscopy. The thermoplastic elastomer is based on polybutadiene with statistically distributed side groups which form an anisotropic supramolecular structure via hydrogen bonds. Changes in the IR spectra at elevated temperatures are related to the melting of the ordered structure. The uniaxial deformation behaviour is studied by linear dichroism Fourier-transform (FT)-IR spectroscopy. A deformation model is developed which accounts for the major experimental results: while the polybutadiene segments behave as flexible chains with characteristic rubberlike elasticity the polar units within the supramolecular structure show an orientation behaviour characteristic for rodlike molecules. 相似文献
72.
Jutta Pauli Robert Brehm Monika Spieles Werner A. Kaiser Ingrid Hilger Ute Resch-Genger 《Journal of fluorescence》2010,20(3):681-693
Aiming at the identification of new fluorescent reporters for targeted optical probes, we assessed the application-relevant
features of a novel asymmetric cyanine, DY-681, in comparison to the only clinically approved dye indocyanine green (ICG),
the golden imaging standard Cy5.5, and the asymmetric cyanine DY-676 successfully exploited by us for the design of different
contrast agents. This comparison included the analysis of the spectroscopic properties of the free fluorophores and their
thermal stability in aqueous solution as well as their cytotoxic potential. In addition, the absorption and emission features
of IgG-conjugated DY-681 were examined. The trimethine DY-681 exhibited spectral features closely resembling that of the pentamethine
Cy5.5. Its high thermal stability in phosphate buffer saline (PBS) solution in conjunction with its low cytotoxicity, reaching
similar values as determined for Cy5.5 and DY-676, renders this dye more attractive as ICG and, due to its improved fluorescence
quantum yield in PBS, also superior to DY-676. Although in PBS, Cy5.5 was still more fluorescent, the fluorescence quantum
yields (Φ
f) of DY-681 and Cy5.5 in PBS containing 5 mass-% bovine serum albumin (BSA) were comparable. Labeling experiments with DY-681
and the model antibody IgG revealed promisingly high Φ
f values of the bioconjugated dye. 相似文献
73.
H. Tatlisu V. Balek I. N. Beckman N. Kardjilov A. Hilger H. Rauch 《Journal of Thermal Analysis and Calorimetry》2012,107(2):447-452
The aim of this study is to characterize the microstructure and high temperature induced structural changes within fiber reinforced
silicon carbide (SiCf/SiC) composites by means of non-destructive techniques. In order to understand their properties, the characterization of
the microstructure of SiCf/SiC composites is the crucial issue. Porosity within composites is unavoidable with currently available manufacturing processes,
and reduces significantly the life time and performance of the composites under harsh environments. Moreover, the internal
pores, created in the manufacturing process cause the degradation most of the outstanding properties such as thermal conductivity,
mechanical properties at high temperature, and radiation stability. Cold neutron tomography and diffusion structural diagnostic
techniques were applied in the investigation of the microstructure of SiCf/SiC composites to gain complementary information. One of the main obstacles to using these composites in fusion technology
and other applications are a change of the porous structure and a swelling at high temperatures and in a severe radiation
environment. Cold neutron tomography enables visualization of the microstructure of the composite and consequently the pore
distributions within the SiCf/SiC composite were observed with a suitable resolution. The diffusion structural diagnostic technique was used to characterize
the thermal behavior of SiCf/SiC composites on heating up to 1300 °C. 相似文献
74.
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77.
Surface plasmon polaritons in nanoparticles were used as a sensitive indicator of structural and electronic properties of
metallic nanoparticles deposited upon various dielectric substrates. Quantum size and cluster–substrate interactions were
separated. The latter were modelled with the dynamic charge transfer effect. For calibration purposes, the free surfaces of
the same clusters exposed to a UHV beam were also investigated. The particles were slightly deformed during deposition; their
final shapes and, in particular, their contact areas were determined. The width of the plasmon excitation band was roughly
doubled compared to that of the free particles, but proved to depend only slightly on the chemical nature of the substrates,
in drastic contrast to the case of fully embedded particles. The analogy holds for the dephasing lifetimes. One reason for
this is that the contact area varies strongly with the substrate material, while it is constant in systems of matrix-embedded
particles.
Received: 26 July 2001 / Revised version: 10 September 2001 / Published online: 15 October 2001 相似文献
78.
R. Hergt R. Hiergeist M. Zeisberger G. Glckl W. Weitschies L. P. Ramirez I. Hilger W. A. Kaiser 《Journal of magnetism and magnetic materials》2004,280(2-3):358-368
Aqueous ferrofluids of maghemite nanoparticles coated with carboxydextran were investigated with respect to their specific loss power (SLP) in dependence on frequency and field amplitude of magnetic AC-fields. In order to elucidate the effect of the size distribution on SLP fluid fractions with different mean particle core size were prepared by a magnetic separation procedure from the original ferrofluid. Structural characterisation by means of TEM and XRD as well as reconstruction of core size distributions from magnetisation curves reveals that the narrow size distributions of the fractions cover a range of mean core sizes from about 8 up to 20 nm. Spectra of the complex susceptibility were measured for a frequency range of 20 Hz to 1 MHz. From the imaginary part of the susceptibility the specific loss power is calculated in dependence on frequency. The results are compared with calorimetrical measurements performed in dependence on field amplitude up to 11 kA/m at 410 kHz. A very high specific loss power in the order of 400 W per gram maghemite was found at 410 kHz and 11 kA/m for the fluid fraction having the largest mean core diameter. A deviation from linear response behaviour is found for this sample showing a power law field dependence of the specific loss power SLPH2.5. In addition to liquid suspensions measurements were performed with particles immobilised in mannitol or gel in order to elucidate the role of Brownian relaxation. The experimentally found dependence of SLP on the mean particle core diameter may be understood in the frame of the Debye dispersion model. Results are discussed with respect to applications of ferrofluids in RF-magnetic hyperthermia. 相似文献
79.
A. Bömer M. Mansfeld K. Winter C. Virchow A. Forster R. Riechelmann E. von Raumer A. Juckenack A. Hilger H. Kreis O. Wolf F. Zetsche O. Foerster E. Rudin F. Wirthle R. Burian und L. Tschugaern 《Fresenius' Journal of Analytical Chemistry》1902,41(10):637-648
Ohne Zusammenfassung 相似文献
80.