[en] We report photoemission and low energy electron diffraction (LEED) data of a C₆₀ multilayer adsorbed on Ge(1 1 1)-c(2x8) surface, as a function of annealing temperature. Remarkable changes take place in the valence band (VB) as the temperature is increased. Three phases are revealed, with different LEED patterns, coverages and molecular distance, including a 'bulk-like' C₆₀ hexagonal single layer, not observed so far, the 3√3x3√3R30 deg. and √13x√13R14 deg. phases already known from literature. The ultra-violet VB spectra show strong similarities with C₆₀ adsorbed on Si surfaces, with the splitting of the C₆₀ highest occupied molecular orbital (HOMO) derived bands into two peaks, due to the C₆₀ bonding with the substrate. The bond is activated by the temperature and implies molecular deformation. At ∼700 deg. C the C₆₀ features disappear and core level photoemission spectra indicate carbon desorption or interdiffusion into the substrate

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[en] The separation of Sr²⁺ from dilute and trace solutions of low activity by means of hollow fiber Amicon ultrafiltration membranes is studied. The cation is absorbed on colloidal particles of titanium oxide formed directly in solution, and the coloidal dispersion is filtrated. The method has been studied under several different operative conditions (pH, Ti/Sr ratio, the presence of interfering ions, colloid formation time) with the aim of determining the optimum conditions to develop a separation process

[en] Laboratory and field tests have been performed on a new passive device, properly designed for the collection of volatile organic compounds from ambient air on an active charcoal layer. Tests performed in order to determine accuracy and precision, response linearity and employment limits show that this device may be helpful in long and medium-time determinations of BTX (benzene, toluene and xylenes) in the atmosphere. The sampler is optimised for a four weeks sampling in open air

[en] A new method of preparing vaginal molds for afterloading intracavitary brachytherapy is described. Our technique makes it possible to obtain the most accurate individualization of therapy as far as dose distribution is concerned by taking into account the patient's anatomy and target volume

[en] We present a study of the thermal evolution of the Ag/Ge(1 1 1) interface by combining Scanning Electron Microscopy (SEM), Low Energy Electron Diffraction (LEED), Spatially Resolved Auger Electron Spectroscopy (SR-AES), and Atomic Force Microscopy (AFM). We followed the morphological and structural changes of a thick Ag film grown onto Ge(1 1 1)-c(2x8) at 300 K after annealing at selected temperatures between 370 and 800 K. The morphology of the system evolves from a flat film up to the nucleation of islands through the formation of dendritic structures. The diffraction pattern shows different intermediate surface reconstructions. We report evidences of Ge intermixing into the Ag growing layer and segregation on top of it

[en] We present results on model based quantification of electron energy loss spectra (EELS), focusing on the factors that influence accuracy and precision in determining chemical concentrations. Several sources of systematical errors are investigated. The spectrometer entrance aperture determines the collection angle, and the effects of its position with respect to the transmitted beam are investigated, taking into account the diffraction by the crystal structure. The effect of the orientation of the sample is tested experimentally and theoretically on SrTiO₃, and finally, a simulated experiment on c-BN at different thicknesses confirms the superior results of the model based method with respect to the conventional method. A test on a set of experimental reference compounds is presented, showing that remarkably good accuracy can be obtained. Recommendations are given to achieve high accuracy and precision in practice

[en] Correlated noise is generally present in experimentally recorded electron energy loss spectra due to a non-ideal electron detector. In this contribution we describe a method to experimentally measure the noise properties of the detector as well as the consequences it has for model-based quantification using maximum likelihood. The effect of the correlated noise on the maximum likelihood fitting results can be shown to be negligible for the estimated (co)variance of the parameters while an experimentally obtained scaling factor is required to correct the likelihood ratio test for the reduction of noise power with frequency. Both effects are derived theoretically under a set of approximations and tested for a range of signal-to-noise values using numerical experiments. Finally, an experimental example shows that the correction for correlated noise is essential and should always be included in the fitting procedure

[en] An extension to model-based electron energy loss spectroscopy (EELS) quantification is reported to improve the possibility of modelling fine structure changes in electron energy loss spectra. An equalisation function is used in the energy loss near edge structure (ELNES) region to model the differences between a single atom differential cross section and the cross section for an atom in a crystal. The equalisation function can be shown to approximate the relative density of unoccupied states for the given excitation edge. On a set of 200 experimental h-BN spectra, this technique leads to statistically acceptable models resulting into unbiased estimates of relative concentrations and making the estimated precisions come very close to the Cramer-Rao lower bound (CRLB). The method greatly expands the useability of model-based EELS quantification to spectra with pronounced fine structure. Another benefit of this model is that one also gets an estimate of the unoccupied density of states for a given excitation edge, without having to do background removal and deconvolution, making the outcome intrinsically more reliable and less noisy

[en] Different deconvolution methods for removing multiple scattering and instrumental broadening from core loss electron energy loss spectra are compared with special attention to the artefacts they introduce. The Gaussian modifier method, Wiener filter, maximum entropy, and model based methods are described. Their performance is compared on virtual spectra where the true single scattering distribution is known. A test on experimental spectra confirms the good performance of model based deconvolution in comparison to maximum entropy methods and shows the advantage of knowing the estimated error bars from a single spectrum acquisition.