Search results for "RADIATION"
showing 10 items of 5298 documents
Hydrodynamic chromatography of macromolecules on small spherical non-porous silica particles
1990
Abstract Non-porous silica spheres with sizes in the range 1.4–2.7 μm were applied as packings for the hydrodynamic chromatography (HDC) of macromolecules. Highly efficient columns, with a reduced plate height below 2, were packed with these small particles. Up to molecular weights of 10 6 the elution behaviour of polystyrenes agreed very well with existing theoretical models. However, for larger polystyrenes the flow-rate exerted an influence on the relative peak positions. The applicability of HDC to rapid separations of soluble macromolecules and inorganic colloids was demonstrated.
Anomale röntgenstreuung zur erforschung makromolekularer strukturen
1982
The possibilities of anomalous X-ray scattering for the investigation of semi- or noncrystalline macromolecular structures are discussed on the grounds of the first successful measurements of anomalous scattering of iron in dissolved hemoglobin. As anomalous scattering of this kind of material is limited to the near vicinity of the X-ray absorption edges, the use of synchrotron radiation appears to be obligatory. The anomalous dispersion of the atomic form factors slightly increases with the atomic number. Anomalous dispersion is nearly doubled when going from the K-absorption edge to the LIII-absorption edge and from there to the Mv- absorption edge. Therefore, the use of anomalous dispers…
Long-Range Order Induced by Intrinsic Repulsion on an Insulating Substrate
2015
An ordered arrangement of molecular stripes with equidistant appearance is formed upon the adsorption of 3-hydroxybenzoic acid onto calcite (10.4) held at room temperature. In a detailed analysis of the next-neighbor stripe distances measured in noncontact atomic force microscopy images at various molecular coverages, we compare the observed stripe arrangement with a random arrangement of noninteracting stripes. The experimentally obtained distance distribution deviates substantially from what is expected for a random distribution of noninteracting stripes, providing direct evidence for the existence of a repulsive interaction between the stripes. At low molecular coverage, where the averag…
Interpretation of capacitance spectra and transit times of single carrier space-charge limited transport in organic layers with field-dependent mobil…
2007
The ac impedance characteristics of a single carrier with space-charge limited current (SCLC) transport in organic layers with field-dependent mobility is analyzed, indicating the similarities as well as the differences to the constant mobility case. The model provides capacitance spectra and transit times from different calculation methods, in relation to the electric field distribution in the SCLC regime. It is found that the low frequency capacitance lies in the range 3Cg/4 < Cif < Cg, with respect to the geometric capacitance Cg. An approximated expression for the variation of the transit time with applied bias is derived, in good agreement with exact calculations. Experimental results …
First-principles simulations of the electronic density of states for superionic Ag2CdI4 crystals
2011
Abstract Energy band dispersion calculations have been performed for Ag 2 CdI 4 superionic within a framework of local density approximation (Perdew–Zunger parameterization) exploiting the first-principles CASTEP computer code. The ab-initio electronic structure simulations were performed for both ( I 4 and I 42 m ) types of e -Ag 2 CdI 4 crystalline structures. Principal optical functions as well as the density of electronic states in the spectral range of inter-band optical transitions (2.5 eV–20 eV) were determined. Theoretically calculated absorption coefficients derived from the obtained band structure are compared with appropriate experimental data.
Transient color centers in complex oxide crystals
2005
The present work is devoted to investigation of induced by a pulsed electron beam (E = 0.25 MeV, τ = 10 ns) transient color centers in pure Gd3Ga5O12, YAlO3 and LiNbO3 single crystals. The relaxation of induced absorption of the crystals was studied within 0-5000 ns range. The origin and nature of transient color centers responsible for induced absorption was discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic self-assembly of photo-switchable nanoparticles
2012
Nanoparticles functionalized with photo-switchable ligands can be assembled into a broad range of structures by controlled light exposure. In particular, alternating light exposures provide the means to control formation of assemblies of various sizes and symmetries. Here, we use scaling arguments and Kinetic Monte Carlo simulations to study the evolution of reversible aggregates in a solution of periodically irradiated photo-switchable nanoparticles. Scaling estimates of the characteristic size and the mean separation of aggregates agree with the simulations. The transition probabilities in the Kinetic Monte Carlo scheme are derived from a renormalized master equation of the diffusion proc…
Ge-doping dependence of gamma-ray induced germanium lone pair centers in Ge-doped silica
2008
We report an experimental study on the y irradiation effects in Ge-doped sol-gel silica samples doped with Ge from 10 2 up to 10 4 part per million molar. The samples were exposed to the radiation generated by a 60 Co source up to an accumulated dose value of 10 MGy. Our data evidence that the γ irradiation significantly increases the number of Germanium Lone Pair Centers (GLPC). Such defects are induced with a concentration that depends on the Ge content of the employed material in those samples where no optical activity related to -s GLPC was detected before irradiation. Furthermore an increase of the GLPC concentration was detected also in a sample that already contains this defect after…
UV LED Photo Electron Ionisation for MS and IMS
2009
AbstractA new MEMS ionisation source for spectrometry is presented on the basis of photo electron emission in silicon MEMS. Lanthanum hexaboride ceramic sample and thin nanolayer proved their suitability for photo electron emission in the desired photon energy range of 3.1eV to 3.9eV which correspond to industrially available UV LED. This ionisation source alternative to a Photoionisationdetector (PID) is inspected of its gas ionisation behaviour using gases with an ionisation potential over and under an energy of 10,6eV. To enable the ionisation of the gases the emitted electrons were accelerated to a well-defined energy. The results of these investigations are comparable to the UV dischar…
Electronic spectra of tetrathiafulvalene and its radical cation: analysis of the performance of the time-dependent DFT approach
2002
Abstract The electronic spectra of tetrathiafulvalene and its radical cation have been studied within the framework of the time-dependent density functional theory by using a conventional hybrid functional. The behaviour of the method has been analyzed through the computed vertical excitation energies for the low-lying electronic excited states. Although the procedure provides a correct description of many of the features of the spectra, deviations in the range 0.4–0.7 eV have been obtained for several transitions, from which one can conclude misleading assignments.