4,111 research outputs found
Atomic data for neutron-capture elements III. Charge transfer rate coefficients for low-charge ions of Ge, Se, Br, Kr, Rb, and Xe
We present total and final-state resolved charge transfer (CT) rate
coefficients for low-charge Ge, Se, Br, Kr, Rb, and Xe ions reacting with
neutral hydrogen over the temperature range 10^2--10^6 K. Each of these
elements has been detected in ionized astrophysical nebulae, particularly
planetary nebulae. CT rate coefficients are a key ingredient for the ionization
equilibrium solutions needed to determine total elemental abundances from those
of the observed ions. A multi-channel Landau Zener approach was used to compute
rate coefficients for projectile ions with charges q=2-5, and for
singly-charged ions the Demkov approximation was utilized. Our results for
five-times ionized species are lower limits, due to the incompleteness of level
energies in the NIST database. In addition, we computed rate coefficients for
charge transfer ionization reactions between the neutral species of the above
six elements and ionized hydrogen. The resulting total and state-resolved CT
rate coefficients are tabulated and available at the CDS. In tandem with our
concurrent investigations of other important atomic processes in photoionized
nebulae, this work will enable robust investigations of neutron-capture element
abundances and nucleosynthesis via nebular spectroscopy.Comment: 11 pages, 4 figures, accepted for publication in Astronomy &
Astrophysic
Macroservers: An Execution Model for DRAM Processor-In-Memory Arrays
The emergence of semiconductor fabrication technology allowing a tight coupling between high-density DRAM and CMOS logic on the same chip has led to the important new class of Processor-In-Memory (PIM) architectures. Newer developments provide powerful parallel processing capabilities on the chip, exploiting the facility to load wide words in single memory accesses and supporting complex address manipulations in the memory. Furthermore, large arrays of PIMs can be arranged into a massively parallel architecture. In this report, we describe an object-based programming model based on the notion of a macroserver. Macroservers encapsulate a set of variables and methods; threads, spawned by the activation of methods, operate asynchronously on the variables' state space. Data distributions provide a mechanism for mapping large data structures across the memory region of a macroserver, while work distributions allow explicit control of bindings between threads and data. Both data and work distributuions are first-class objects of the model, supporting the dynamic management of data and threads in memory. This offers the flexibility required for fully exploiting the processing power and memory bandwidth of a PIM array, in particular for irregular and adaptive applications. Thread synchronization is based on atomic methods, condition variables, and futures. A special type of lightweight macroserver allows the formulation of flexible scheduling strategies for the access to resources, using a monitor-like mechanism
A shifting paradigm: teachers' beliefs and methods for fostering ecological literacy in two public charter schools
Thesis (M.Ed.) University of Alaska Fairbanks, 2015Ecological literacy is measured by a person's ability to understand the natural systems that make life on earth possible and how to live in accordance with those systems. The emergence of the pedagogies of place- and community-based education during the past two decades provides a possible avenue for fostering ecological literacy in schools. This thesis explores the following research questions: 1) How is ecological literacy fostered in two Alaskan public charter schools? 2) What are teachers' beliefs in these two schools about the way children and youth develop ecological literacy? 3) What are effective teaching methods and what are the challenges in engaging students in ecological literacy? Semi-structured interviews were conducted with six K-12 teachers in two public charter schools in Alaska in order to investigate these questions, and relevant examples of student work were collected for study as well. Qualitative data analysis revealed several emergent themes: the need for real-world connections to curriculum; the necessity of time spent outdoors at a young age; the long-term and holistic nature of ecological literacy development; and the importance of family and community role models in developing connections with the natural world. Based upon the research findings, several recommendations are made to support the efforts of teachers in these schools and elsewhere for fostering ecological literacy in children and youth
Model der Schelde van Hansweert tot aan de Boudewijnsluis: overzicht der uitgevoerde proeven betreffende de normalisatiewerken te Bath. 1ste vervolg
Model der Schelde van Hansweert tot Oosterweel: proeven in verband met kalibreringswerken op de Schelde in de omgeving van de nieuwe zeesluis te Zandvliet
Model der Schelde van Hansweert tot Oosterweel: proeven in verband met de dwarsstromen bij maximum vloed ter hoogte van de uitloop van het Schaar van Zimmermanpolder
Model der Schelde van Hansweert tot aan de Boudewijnsluis: proeven in verband met de normalisatiewerken van de Schelde in de omgeving van Bath. 3de deel
Model der Schelde van Hansweert tot aan de Boudewijnsluis: proeven in verband met normalisatiewerken van de Schelde in de omgeving van Bath. 2e deel
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