583 research outputs found

    A Method to Determine the In-Air Spatial Spread of Clinical Electron Beams

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    We propose and analyze in detail a method to measure the in-air spatial spread parameter of clinical electron beams. Measurements are performed at the center of the beam and below the adjustable collimators sited in asymmetrical configuration in order to avoid the distortions due to the presence of the applicator. The main advantage of our procedure lies in the fact that the dose profiles are fitted by means of a function which includes, additionally to the Gaussian step usually considered, a background which takes care of the dose produced by different mechanisms that the Gaussian model does not account for. As a result, the spatial spread is obtained directly from the fitting procedure and the accuracy permits a good determination of the angular spread. The way the analysis is done is alternative to that followed by the usual methods based on the evaluation of the penumbra width. Besides, the spatial spread found shows the quadratic-cubic dependence with the distance to the source predicted by the Fermi-Eyges theory. However, the corresponding values obtained for the scattering power are differing from those quoted by ICRU nr. 35 by a factor ~2 or larger, what requires of a more detailed investigation.Comment: 11 pages, 5 Postscript figures, to be published in Medical Physic

    arf3DS4: An Integrated Framework for Localization and Connectivity Analysis of fMRI Data

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    In standard fMRI analysis all voxels are tested in a massive univariate approach, that is, each voxel is tested independently. This requires stringent corrections for multiple comparisons to control the number of false positive tests (i.e., marking voxels as active while they are actually not). As a result, fMRI analyses may suffer from low power to detect activation, especially in studies with high levels of noise in the data, for example developmental or single-subject studies. Activated region fitting (ARF) yields a solution by modeling fMRI data by multiple Gaussian shaped regions. ARF only requires a small number of parameters and therefore has increased power to detect activation. If required, the estimated regions can be directly used as regions of interest in a functional connectivity analysis. ARF is implemented in the R package arf3DS4. In this paper ARF and its implementation are described and illustrated with an example

    Everyday experiences of people living with MCI or dementia:A scoping review

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    Background Increasing attention has been paid to the ‘voice’ of people living with MCI or dementia, but there is a lack of clarity about how everyday life is exercised, lived, and understood from this insider’s perspective. The current study aimed to explore and identify the everyday life experiences, challenges and facilitators, of home living individuals with MCI and dementia. Method Our study adopted a scoping review methodology, guided by the Joanna Briggs Institute Reviewers Manual. Eight databases were searched, resulting in 6345 records, of which 58 papers were included in the review. Only qualitative studies were included, published between 2011 and 2021. Analysis was done by descriptive content analysis. Result Included study characteristics are summarized in Table 1. Our findings were categorized into seven spheres of everyday life: experiences related to the condition, the self, relationships, activities, environment, health and social care, and public opinions [Figure 1, Table 2]. Results show the many disruptions and losses in everyday life and the ways people try to adapt to these changes. Highlighted in every area is the importance of reciprocal relationships and being engaged as citizens in the community in a meaningful way. Included studies showed no differences between groups in the impact on the experience of everyday life, such as between MCI and dementia. Conclusion This review shows that the change of focus from healthcare to all aspects of everyday life provides insight into the insider’s perspective of people living with dementia. The majority of included studies emphasize the social needs of people living with MCI or dementia. All areas of everyday life seem to be closely intertwined and reflect an socioecological model [1], [2], [3]. Furthermore, perhaps one of the defining aspects of MCI according to the current definition, that symptoms do not interfere with daily life, requires more nuance. More research is needed on factors that promote and impede the sense of reciprocity and belonging, as experienced by people living with MCI and dementia

    Binomial level densities

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    It is shown that nuclear level densities in a finite space are described by a continuous binomial function, determined by the first three moments of the Hamiltonian, and the dimensionality of the underlying vector space. Experimental values for 55^{55}Mn, 56^{56}Fe, and 60^{60}Ni are very well reproduced by the binomial form, which turns out to be almost perfectly approximated by Bethe's formula with backshift. A proof is given that binomial densities reproduce the low moments of Hamiltonians of any rank: A strong form of the famous central limit result of Mon and French. Conditions under which the proof may be extended to the full spectrum are examined.Comment: 4 pages 2 figures Second version (previous not totally superseeded

    Highly deformed 40^{40}Ca configurations in 28^{28}Si + 12^{12}C

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    The possible occurrence of highly deformed configurations in the 40^{40}Ca di-nuclear system formed in the 28^{28}Si + 12^{12}C reaction is investigated by analyzing the spectra of emitted light charged particles. Both inclusive and exclusive measurements of the heavy fragments (A \geq 10) and their associated light charged particles (protons and α\alpha particles) have been made at the IReS Strasbourg {\sc VIVITRON} Tandem facility at bombarding energies of Elab(28E_{lab} (^{28}Si) = 112 MeV and 180 MeV by using the {\sc ICARE} charged particle multidetector array. The energy spectra, velocity distributions, and both in-plane and out-of-plane angular correlations of light charged particles are compared to statistical-model calculations using a consistent set of parameters with spin-dependent level densities. The analysis suggests the onset of large nuclear deformation in 40^{40}Ca at high spin.Comment: 33 pages, 11 figure
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