Empirical description of beta-delayed fission partial half-lives

Background: The process of beta-delayed fission (bDF) provides a versatile tool to study low-energy fission in nuclei far away from the beta-stability line, especially for nuclei which do not fission spontaneously. Purpose: The aim of this paper is to investigate systematic trends in bDF partial half-lives. Method: A semi-phenomenological framework was developed to systematically account for the behavior of bDF partial half-lives. Results: The bDF partial half-life appears to exponentially depend on the difference between the Q value for beta decay of the parent nucleus and the fission-barrier energy of the daughter (after beta decay) product. Such dependence was found to arise naturally from some simple theoretical considerations. Conclusions: This systematic trend was confirmed for experimental bDF partial half-lives spanning over 7 orders of magnitudes when using fission barriers calculated from either the Thomas-Fermi or the liquid-drop fission model. The same dependence was also observed, although less pronounced, when comparing to fission barriers from the finite-range liquid-drop model or the Thomas-Fermi plus Strutinsky Integral method.Comment: accepted for publication in Phys. Rev.

Cost-effectiveness of counselling, graded-exercise and usual care for chronic fatigue: evidence from a randomised trial in primary care

Fatigue is common and has been shown to result in high economic costs to society. The aim of this study is to compare the cost-effectiveness of two active therapies, graded-exercise (GET) and counselling (COUN) with usual care plus a self-help booklet (BUC) for people presenting with chronic fatigue

Parsec-scale jet properties of the gamma-ray quasar 3C 286

The quasar 3C~286 is one of two compact steep spectrum sources detected by the {\it Fermi}/LAT. Here, we investigate the radio properties of the parsec(pc)-scale jet and its (possible) association with the $\gamma$-ray emission in 3C~286. The Very Long Baseline Interferometry (VLBI) images at various frequencies reveal a one-sided core--jet structure extending to the southwest at a projected distance of $\sim$1 kpc. The component at the jet base showing an inverted spectrum is identified as the core, with a mean brightness temperature of $2.8\times 10^{9}$~K. The jet bends at about 600 pc (in projection) away from the core, from a position angle of $-135^\circ$ to $-115^\circ$. Based on the available VLBI data, we inferred the proper motion speed of the inner jet as $0.013 \pm 0.011$ mas yr$^{-1}$ ($\beta_{\rm app} = 0.6 \pm 0.5$), corresponding to a jet speed of about $0.5\,c$ at an inclination angle of $48^\circ$ between the jet and the line of sight of the observer. The brightness temperature, jet speed and Lorentz factor are much lower than those of $\gamma$-ray-emitting blazars, implying that the pc-scale jet in 3C~286 is mildly relativistic. Unlike blazars in which $\gamma$-ray emission is in general thought to originate from the beamed innermost jet, the location and mechanism of $\gamma$-ray emission in 3C~286 may be different as indicated by the current radio data. Multi-band spectrum fitting may offer a complementary diagnostic clue of the $\gamma$-ray production mechanism in this source.Comment: 9 pages, 4 figures, accept for publication in MNRA

Estão os Alunos de Matrícula Dupla Preparados para Entrar na Faculdade? Evidências do Estudo Nacional de Artes de Wabash

We examine whether dual enrolled students display greater levels of college readiness than nonparticipants. Advocates assert that dual enrollment improves students’ college readiness, but despite these assertions, few researchers have evaluated this relationship. Moreover, researchers that do consider whether dual enrollment improves college readiness examine this relationship while students participate in dual enrollment or shortly thereafter. Unlike traditional measures of college readiness that tend to emphasize the cognitive domain of college readiness, we use measures that integrate both cognitive and noncognitive domains of college readiness. We find that students who participated in dual enrollment tend to be more college ready than those who did not earn college credit in high school. The exception is that there is no statistical difference between dual enrollees and non-accelerators in their key transition knowledge and skills. The magnitude of the dual enrollment effect is second only to gender. Examinamos si los estudiantes de matriculas duales muestran mayores niveles de preparación para la universidad que los que no participan en ese programa. Los defensores afirman que la doble inscripción mejora la preparación para la universidad de los estudiantes, pero a pesar de estas afirmaciones, pocos investigadores han evaluado esta relación. Por otra parte, los investigadores que si consideran que la doble matrícula mejora la preparación universitaria examinan esta relación mientras los estudiantes participan en doble inscripción o poco después. A diferencia de las medidas tradicionales de preparación para la universidad que tienden a enfatizar el dominio cognitivo de preparación para la universidad, utilizamos medidas que integran dominios cognitivos y no-cognitivos de preparación para la universidad. Encontramos que los estudiantes que participaron en la doble matrícula tienden a ser más preparados para la universidad que los que no ganan créditos universitarios en la escuela secundaria. La excepción es que no hay diferencia estadística entre los inscritos en matriculas duales y los que no en conocimientos y habilidades importantes para  los estudios universitarios. El efecto de magnitud de las matriculas duales sólo es superado por el género.Examinamos se os alunos de inscrição duplas mostram níveis mais elevados de preparação para a faculdade do que aqueles que não participam nesse programa. Os defensores argumentam que a dupla inscrição melhor preparação para os estudantes universitários, mas apesar destas afirmações, poucos pesquisadores avaliaram essa relação. Além disso, os pesquisadores acreditam que, se a dupla prontidão faculdade de inscrição melhora a examinar esta relação, enquanto os alunos participam de matrícula dupla ou pouco depois. Ao contrário de medidas tradicionais de prontidão para faculdade que tendem a enfatizar o domínio cognitivo de preparação para a faculdade, usamos medidas que integram domínios cognitivos e não-cognitivas na preparação para a faculdade. Descobrimos que os alunos que participaram do programa da matrícula dupla tendem a estar mais preparados para a faculdade do que aqueles que não ganham créditos universitários na escola. A exceção é que não há diferença estatística entre os alunos de dupla inscrição e os que não em conhecimentos e habilidades importantes para a faculdade. A magnitude do efeito da dupla inscrição só é superado por gênero

An Universal Quantum Network - Quantum CPU

An universal quantum network which can implement a general quantum computing is proposed. In this sense, it can be called the quantum central processing unit (QCPU). For a given quantum computing, its realization of QCPU is just its quantum network. QCPU is standard and easy-assemble because it only has two kinds of basic elements and two auxiliary elements. QCPU and its realizations are scalable, that is, they can be connected together, and so they can construct the whole quantum network to implement the general quantum algorithm and quantum simulating procedure.Comment: 8 pages, Revised versio

Who Contributes to the Knowledge Sharing Economy?

Information sharing dynamics of social networks rely on a small set of influencers to effectively reach a large audience. Our recent results and observations demonstrate that the shape and identity of this elite, especially those contributing \emph{original} content, is difficult to predict. Information acquisition is often cited as an example of a public good. However, this emerging and powerful theory has yet to provably offer qualitative insights on how specialization of users into active and passive participants occurs. This paper bridges, for the first time, the theory of public goods and the analysis of diffusion in social media. We introduce a non-linear model of \emph{perishable} public goods, leveraging new observations about sharing of media sources. The primary contribution of this work is to show that \emph{shelf time}, which characterizes the rate at which content get renewed, is a critical factor in audience participation. Our model proves a fundamental \emph{dichotomy} in information diffusion: While short-lived content has simple and predictable diffusion, long-lived content has complex specialization. This occurs even when all information seekers are \emph{ex ante} identical and could be a contributing factor to the difficulty of predicting social network participation and evolution.Comment: 15 pages in ACM Conference on Online Social Networks 201