Ion-implantation-caused special damage profiles determined by spectroscopic ellipsometry in crystalline and in relaxed (annealed) amorphous silicon

We previously developed a fitting method of several parameters to evaluate ion-implantation-caused damage profiles from spectroscopic ellipsometry (SE) (M. Fried et al., J. Appl. Phys., 71 (1992) 2835). Our optical model consists of a stack of layers with fixed and equal thicknesses and damage levels described by a depth profile function (coupled half Gaussians). The complex refractive index of each layer is calculated from the actual damage level by Bruggeman effective medium approximation (EMA) using crystalline (c-Si) and amorphous (a-Si) silicon as end-points. Two examples are presented of the use of this method with modified optical models. First, we investigated the surface damage formed by room temperature B+ and N+ implantation into silicon. For the analysis of the SE data we added a near surface amorphous layer to the model with variable thickness. Second, we determined 20 keV B+ implantation-caused damage profiles in relaxed (annealed) amorphous silicon. In this special case, the complex refractive index of each layer was calculated from the actual damage level by the EMA using relaxed a-Si and implanted a-Si as end-points. The calculated profiles are compared with Monte Carlo simulations (TRIM code); good agreement is obtained

Topics in Population Imaging : The Rhineland Study

Population imaging is the large-scale data acquisition and analysis of medical images in population-based cohorts. When combined with other data acquired in the cohort, it provides the unique potential to characterise disease burden and identify persons at risk. In setting up new population imaging studies, one has to address several challenges, such as the minimisation of selection bias and how to deal with incidental findings. Population imaging enables the investigation of a wide range of topics of interest, including age-related diseases as cerebral small vessel disease (SVD), of which white matter hyperintensities (WMH) are the archetypical example. In the first part of my thesis, I focus on how to conduct population imaging in an ethically and valid manner. I performed my research in the context of the Rhineland Study. I successfully broadened standard magnetic resonance imaging (MRI) eligibility criteria, allowing eligible participants with medical implants without MRI safety certificate, tattoos and permanent make-up to undergo 3 Tesla MRI. None of the participants reported any adverse events, suggesting that most medical implants, tattoos, and permanent make-up are MRI suitable. Including participants with such indications is crucial to reduce selection bias, thereby improving generalisability of research findings. The handling of incidental findings, i.e., if and which abnormalities should be reported back to participants, requires insights in the frequency and clinical relevance of the finding. I investigated the prevalence and clinical relevance of incidental findings on neuroimaging in the Rhineland Study. While we observed incidental findings in almost 25 % of the participants, only 5 % of the detected abnormalities required diagnostic work-up. In the second part of my thesis, I examine the effect of biological sex and, in women, the effect of menopause on WMH. In the Rhineland Study, I found that sex differences in WMH burden exist, which were modified by menopause. After menopause, women presented with more WMH and a steeper increase in WMH burden with advancing age, compared to premenopausal women and men. I conclude that sex differences need to be considered both in research and clinical practice

Development of Air-cooled Engines with Blower Cooling

With the aid of a heating device, the heat transfer to cylinders with conical fins of various forms is determined both for shrouded and exposed cylinders. Simultaneously the pressure drop for overcoming the resistance to the motion of air between the fins of the enclosed cylinder is measured. Thus the relations between the heat transfer and the energy required for cooling are discovered. The investigations show that the heat transfer in a conducted air flow is much greater than in a free current and that further improvement, as compared with free exposure, is possible through narrower spaces between the fins

Detergent-like actions of linear amphipathic cationic antimicrobial peptides

AbstractAntimicrobial peptides have raised much interest as pathogens become resistant against conventional antibiotics. We review biophysical studies that have been performed to better understand the interactions of linear amphipathic cationic peptides such as magainins, cecropins, dermaseptin, δ-lysin or melittin. The amphipathic character of these peptides and their interactions with membranes resemble the properties of detergent molecules and analogies between membrane-active peptide and detergents are presented. Several models have been suggested to explain the pore-forming, membrane-lytic and antibiotic activities of these peptides. Here we suggest that these might be ‘special cases’ within complicated phase diagrams describing the morphological plasticity of peptide/lipid supramolecular assemblies