Approximation Schemes for Node-Weighted Geometric Steiner Tree Problems

In this paper we introduce a new technique for approximation schemes for geometrical optimization problems. As an example problem, we consider the following variant of the geometric Steiner tree problem. Every point u which is not included in the tree costs a penalty of π(u) units. Furthermore, every Steiner point that we use costs c S units. The goal is to minimize the total length of the tree plus the penalties. Our technique yields a polynomial time approximation scheme for the problem, if the points lie in the plan

HST Observations of the QSO pair Q1026-0045A,B

The spatial distribution of the Ly$\alpha$ forest is studied using new HST data for the quasar pair Q~1026--0045 A and B at $z_{em}$ = 1.438 and 1.520 respectively. The angular separation is 36 arcsec and corresponds to transverse linear separations between lines of sight of $\sim300h^{-1}_{50}$ kpc ($q_{o}$ = 0.5) over the redshift range 0.833 < z < 1.438. From the observed numbers of coincident and anti-coincident Ly$\alpha$ absorption lines, we conclude that, at this redshift, the Ly$\alpha$ structures have typical dimensions of $\sim500h^{-1}_{50}$ kpc, larger than the mean separation of the two lines of sight. The velocity difference, $\Delta V$, between coincident lines is surprisingly small (4 and 8 pairs with $\Delta V < 50 and 200 km/s respectively). Metal line systems are present at$z_{abs}$= 1.2651 and 1.2969 in A,$z_{abs}$= 0.6320, 0.7090, 1.2651 and 1.4844 in B. In addition we tentatively identify a weak Mg II system at$z_{abs}$= 0.11 in B. It is remarkable that the$z_{abs}$= 1.2651 system is common to both lines of sight. The system at$z_{abs}$= 1.4844 There is a metal-poor associated system at$z_{abs}$= 1.4420 along the line of sight to A with complex velocity profile. We detect a strong Ly$\alpha$absorption along the line of sight to B redshifted by only 300 km/s relatively to the associated system. It is tempting to interpret this as the presence of a disk of radius larger than 300$h^{-1}_{50}$ kpc surrounding quasar A.Comment: 4 pages, 2 figures, A&A Letter acccepte

Radon, From the Ground into Our Schools: Parent/Guardian Awareness of Radon Levels in Vermont Schools

Introduction. Radon is the leading cause of lung cancer among non-smokers. Ex- posure to radon in schools may be harmful to schoolchildren, faculty, and staff, but there is currently no legislation mandating testing or mitigation of radon levels in Vermont schools. Objectives. The goal of our study was to assess Vermont parents’ awareness of radon’s harmful effects, as well as awareness of and support for testing and mitigation of radon levels in their children’s schools. Methods. We distributed paper and online surveys to Vermont parents of children grades K-12. 126 surveys were received and quantitatively analyzed. We held a focus group of two Vermont parents to gather qualitative data. Results. Most surveyed parents demonstrated general knowledge of radon, but only 51% believed that radon affects the lungs. 8% were confident that their children’s schools had informed them about radon levels. 91.2% believe their children’s schools should take action to address elevated radon levels and 87% would support mandated mitigation. There is some concern and lack of knowledge about the financial implications of radon mitigation. Conclusions. Most Vermont parents of children grades K-12 are unaware that radon is a lung carcinogen and do not know their children’s school’s radon levels or mitigation status. However, most are in favor of legislation that would require testing and dis- closure of schools’ high radon levels. Educating parents about school radon levels and their association with lung cancer could be a foundation for community support of legislation that mandates testing and mitigation of radon in Vermont schools.https://scholarworks.uvm.edu/comphp_gallery/1252/thumbnail.jp

Literacy in lockdown: learning and teaching in COVID-19 school closures

Across the globe, children have been away from schools and their teachers, but literacy learning has continued. In many countries, children’s literacy proficiency is often measured against high-stakes assessment tests. However, such tests do not make visible children’s literacy lives away from formal learning settings and thus children are positioned as task-responders, rather than as agentive readers and writers. This article explores the fluidity and diversity of literacy events and practices for students, children and their teachers observed during the recent period of Covid-19 lockdown restrictions

Consistency in diagnostic suggestions does not influence the tendency to accept them

Background: Studies suggest that residents tend to accept diagnostic suggestions, which could lead to diagnostic errors if the suggestion is incorrect. Those studies did not take into account that physicians in clinical practice will mainly encounter correct suggestions. The present study investigated residents’ diagnostic performance if they would first encounter a number of correct suggestions followed by a number of incorrect suggestions, and vice versa. It was hypothesized that more incorrect suggestions would be accepted if participants had first evaluated a series of correct suggestions. Method: Residents (n = 38) evaluated suggested diagnoses on eight written clinical cases. Half of the participants first evaluated four correct suggestions and then evaluated four incorrect suggestions (C/I-condition). The other half started with the four incorrect suggestions followed by the correct suggestions (I/C-condition). Results: Our findings show that the evaluation score in the C/I condition (M = 2.87, MSE = 0.14) equaled that in the I/C condition (M = 2.66, MSE = 0.14), F(1,36) = 1.09, p = 0.30, ns, meaning that consistency in preceding suggested diagnoses did not influence the tendency to accept subsequent diagnostic suggestions. There was, however, a significant interaction effect between case order and phase, F(1,36) = 11.82, p = 0.001, ηp2 = 0.25, demonstrating that the score on cases with correct suggestions was higher than the score on cases with incorrect suggestions. Conclusion: These findings indicate that consistency in preceding correct or incorrect diagnostic suggestions did not influence the tendency to accept or reject subsequent suggestions. However, overall residents still showed a tendency to accept diagnostic suggestions, which may lead to diagnostic errors if the suggestion is incorrect

First results from the OSQAR photon regeneration experiment: No light shining through a wall

A new method to amplify the photon-axion conversions in magnetic field is proposed using a buffer gas at a specific pressure. As a first result, new bounds for mass and coupling constant for purely laboratory experiments aiming to detect any hypothetical scalars and pseudo-scalars which can couple to photons were obtained at 95% confidence level, excluding the PVLAS result newly disclaimed.Comment: 4 pages, 5 figure

The promise of a recalibrated Caribbean-European Union Partnership

Números monográficos con título distintivo catalogados individualmente.‎Bajo la denominación "Documentos de trabajo" se publican resultados de los proyectos de investigación realizados y promovidos por el CEALCI. Además pueden ser incluidos en esta serie aquellos trabajos que, previa aceptación por el Consejo Editorial, reunan los requisitos de calidad establecidos y coincidan con los objetivos de la Fundación Carolina y su Centro de Estudios.‎Bibliografía: p. 31-34Resumen: El Caribe y la Unión Europea (UE) mantienen una relación birregional formal desde la firma del Convenio de Lomé en 1975, y son firmes defensores del multilateralismo, de la integración regional, de la democracia y del Estado de derecho, además de reflejar vibrantes políticas multiétnicas y multilingües. La relación birregional ha evolucionado considerablemente en estos 45 años y se refleja en los acuerdos formales entre los Estados de África, el Caribe y el Pacífico (ACP) y la UE, y en el ámbito de la cooperación económica se ha reforzado con la firma del Acuerdo de Asociación Económica Cariforum-UE (CEPA, por sus siglas en inglés) en 2008. La UE también sigue siendo una fuente importante de cooperación al desarrollo para el Caribe, complementada por un régimen sui generis de gestión de proyectos que incluye la programación plurianual. Además, los lazos birregionales se han ampliado a nuevas áreas de esfuerzo multilateral conjunto, como el Acuerdo de Facilitación del Comercio (AFC) de la Organización Mundial del Comercio (OMC) y el Acuerdo de París sobre el Cambio Climático

Flowboard:How Seamless, Live, Flow-Based Programming Impacts Learning to Code for Embedded Electronics

Toolkits like the Arduino system have brought embedded programming to STEM education. However, learning embedded programming is still hard, requiring an understanding of coding, electronics, and how both sides interact. To investigate the opportunities of using a different programming paradigm than the imperative approach to learning embedded coding, we developed Flowboard . Students code in a visual iPad editor using flow-based programming , which is conceptually closer to circuit diagrams than imperative code. Two breadboards with I/O pins mirrored on the iPad connect electronics and program graph more seamlessly than existing IDEs. Program changes take effect immediately. This liveness reflects circuit behavior better than edit-compile-run loops. A first study confirmed that students can solve basic embedded programming tasks with Flowboard while highlighting important differences to a typical imperative IDE, Ardublock. A second, in-depth study provided qualitative insights into Flowboard’s impact on students’ conceptual models of electronics and embedded programming and exploring