138 research outputs found
Lifetime reduction of surface states at Cu, Ag and Au(111) caused by impurity scattering
We present density-functional results on the lifetime of the (111) surface
state of the noble metals. We consider scattering on the Fermi surface caused
by impurity atoms belonging to the 3d and 4sp series. The results are analyzed
with respect to film thickness and with respect to separation of scattering
into bulk or into surface states. While for impurities in the surface layer the
overall trends are similar to the long-known bulk-state scattering, for
adatom-induced scattering we find a surprising behavior with respect to the
adatom atomic number. A plateau emerges in the scattering rate of the 3d
adatoms, instead of a peak characteristic of the d resonance. Additionally, the
scattering rate of 4sp adatoms changes in a zig-zag pattern, contrary to a
smooth parabolic increase following Linde's rule that is observed in bulk. We
interpret these results in terms of the weaker charge-screening and of
interference effects induced by the lowering of symmetry at the surface
Community Schools Unfolded: A review of the literature.
Community schools are quickly increasing in number, but there is no evidence whether they are more effective than traditional schools. No study has empirically compared community schools to other schools. This study reviews the literature on the effectiveness of community schools. We focus on their three main components: cooperation with external organizations, parental involvement, and extracurricular activities. This review indicates that involving external organizations seems valuable in terms of social cohesion in neighborhoods. Parental involvement is particularly important for the educational development of lower socio-economic status families. Extracurricular activities positively relate to students? development in academic and social terms.
Fast parallel algorithms for a broad class of nonlinear variational diffusion approaches
Variational segmentation and nonlinear diffusion approaches have been very active research areas in the fields of image processing and computer vision during the last years. In the present paper, we review recent advances in the development of efficient numerical algorithms for these approaches. The performance of parallel implement at ions of these algorithms on general-purpose hardware is assessed. A mathematically clear connection between variational models and nonlinear diffusion filters is presented that allows to interpret one approach as an approximation of the other, and vice versa. Numerical results confirm that, depending on the parametrization, this approximation can be made quite accurate. Our results provide a perspective for uniform implement at ions of both nonlinear variational models and diffusion filters on parallel architectures
Optical sensory arrays for the detection of urinary bladder cancerârelated volatile organic compounds
Large expert-curated database for benchmarking document similarity detection in biomedical literature search
Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term FrequencyâInverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research
MEGâEEG Information Fusion and Electromagnetic Source Imaging: From Theory to Clinical Application in Epilepsy
Current therapeutic strategies of heterotopic ossification â a survey amongst orthopaedic and trauma departments in Germany
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