Liquid nitrogen blackbody for spectral emittance studies

Cryogenic black body used in spectral emittance of rock

Consistency of spectroscopic factors from (e,e'p) reactions at different momentum transfers

The possibility to extract relevant information on spectroscopic factors from (e,e$'$p) reactions at high $Q^2$ is studied. Recent ${}^{16}$O(e,e$'$p) data at $Q^2 = 0.8$ (GeV/$c)^2$ are compared to a theoretical approach which includes an eikonal description of the final-state interaction of the proton, a microscopic nuclear matter calculation of the damping of this proton, and high-quality quasihole wave functions for $p$-shell nucleons in ${}^{16}{\rm O}$. Good agreement with the $Q^2 = 0.8$ (GeV/$c)^2$ data is obtained when spectroscopic factors are employed which are identical to those required to describe earlier low $Q^2$ experiments.Comment: 17 pages, 6 figures in .eps format, submitted to Phys. Rev.

Saturation of nuclear matter and short-range correlations

A fully self-consistent treatment of short-range correlations in nuclear matter is presented. Different implementations of the determination of the nucleon spectral functions for different interactions are shown to be consistent with each other. The resulting saturation densities are closer to the empirical result when compared with (continuous-choice) Brueckner-Hartree-Fock values. Arguments for the dominance of short-range correlations in determining the nuclear-matter saturation density are presented. A further survey of the role of long-range correlations suggests that the inclusion of pionic contributions to ring diagrams in nuclear matter leads to higher saturation densities than empirically observed. A possible resolution of the nuclear-matter saturation problem is suggested.Comment: 5 pages, 1 figure, to be published in Phys.Rev.Let

Largest Lyapunov Exponent for Many Particle Systems at Low Densities

The largest Lyapunov exponent $\lambda^+$ for a dilute gas with short range interactions in equilibrium is studied by a mapping to a clock model, in which every particle carries a watch, with a discrete time that is advanced at collisions. This model has a propagating front solution with a speed that determines $\lambda^+$, for which we find a density dependence as predicted by Krylov, but with a larger prefactor. Simulations for the clock model and for hard sphere and hard disk systems confirm these results and are in excellent mutual agreement. They show a slow convergence of $\lambda^+$ with increasing particle number, in good agreement with a prediction by Brunet and Derrida.Comment: 4 pages, RevTeX, 2 Figures (encapsulated postscript). Submitted to Phys. Rev. Let

COVID-19 publications: Database coverage, citations, readers, tweets, news, Facebook walls, Reddit posts

© 2020 The Authors. Published by MIT Press. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1162/qss_a_00066The COVID-19 pandemic requires a fast response from researchers to help address biological, medical and public health issues to minimize its impact. In this rapidly evolving context, scholars, professionals and the public may need to quickly identify important new studies. In response, this paper assesses the coverage of scholarly databases and impact indicators during 21 March to 18 April 2020. The rapidly increasing volume of research, is particularly accessible through Dimensions, and less through Scopus, the Web of Science, and PubMed. Google Scholar’s results included many false matches. A few COVID-19 papers from the 21,395 in Dimensions were already highly cited, with substantial news and social media attention. For this topic, in contrast to previous studies, there seems to be a high degree of convergence between articles shared in the social web and citation counts, at least in the short term. In particular, articles that are extensively tweeted on the day first indexed are likely to be highly read and relatively highly cited three weeks later. Researchers needing wide scope literature searches (rather than health focused PubMed or medRxiv searches) should start with Dimensions (or Google Scholar) and can use tweet and Mendeley reader counts as indicators of likely importance

Supporting resilience in chldren and youth impacted by complex trauma

Exposure to repeated traumatic events, including abuse, neglect, and domestic and community violence is often referred to as complex trauma. This research was conducted to better understand the developmental impact of complex trauma on children and adolescents, and to consider what treatment approach might best serve this population. The author first examined the impact of repeated victimization on child neurobiological development, with particular attention to the areas of attachment, affect regulation, behavioral control, cognition, and self-esteem. Complex trauma treatments that are more individually focused and grounded in cognitive-behavioral theory were then compared to those that are more systems-focused and stem from attachment and intersubjective theories. This author found that most of the literature agrees on the following core components of treatment for youth with complex trauma histories: safety, selfregulation, self-reflective information processing, traumatic experiences integration, and relational engagement. An area that seems to be getting increasing attention is treatment directed at fostering strengths and building competencies. The author concluded that including a caregiver in as much of the treatment as possible can support attachment and lead to longer-term positive gains. The author found that both approaches offer potentially effective interventions, and combining components from both can result in a more comprehensive treatment approach. This study includes a case example and a discussion of implications for clinical social work practice with a focus on cultural considerations as well as recommendations for further research

Fitness Correlates Of Song Repertoire Size In Free-Living Song Sparrows (Melospiza Melodia)

Models of sexual selection propose that exaggerated secondary sexual ornaments indicate a male\u27s own fitness and the fitness of his offspring. These hypotheses have rarely been thoroughly tested in free-living individuals because overall fitness, as opposed to fitness components, is difficult to measure. We used 20 years of data from song sparrows ( Melospiza melodia) inhabiting Mandarte Island, British Columbia, Canada, to test whether a male\u27s song repertoire size, a secondary sexual trait, predicted overall measures of male or offspring fitness. Males with larger song repertoires contributed more independent and recruited offspring, and independent and recruited grandoffspring, to Mandarte\u27s population. This was because these males lived longer and reared a greater proportion of hatched chicks to independence from parental care, not because females mated to males with larger repertoires laid or hatched more eggs. Furthermore, independent offspring of males with larger repertoires were more likely to recruit and then to leave more grandoffspring than were offspring of males with small repertoires. Although we cannot distinguish whether observed fitness variation reflected genetic or environmental effects on males or their offspring, these data suggest that female song sparrows would gain immediate and intergenerational fitness benefits by pairing with males with large song repertoires

Spelling in adolescents with dyslexia: errors and modes of assessment

In this study we focused on the spelling of high-functioning students with dyslexia. We made a detailed classification of the errors in a word and sentence dictation task made by 100 students with dyslexia and 100 matched control students. All participants were in the first year of their bachelor’s studies and had Dutch as mother tongue. Three main error categories were distinguished: phonological, orthographic, and grammatical errors (on the basis of morphology and language-specific spelling rules). The results indicated that higher-education students with dyslexia made on average twice as many spelling errors as the controls, with effect sizes of d ≥ 2. When the errors were classified as phonological, orthographic, or grammatical, we found a slight dominance of phonological errors in students with dyslexia. Sentence dictation did not provide more information than word dictation in the correct classification of students with and without dyslexia