A line-binned treatment of opacities for the spectra and light curves from neutron star mergers

The electromagnetic observations of GW170817 were able to dramatically increase our understanding of neutron star mergers beyond what we learned from gravitational waves alone. These observations provided insight on all aspects of the merger from the nature of the gamma-ray burst to the characteristics of the ejected material. The ejecta of neutron star mergers are expected to produce such electromagnetic transients, called kilonovae or macronovae. Characteristics of the ejecta include large velocity gradients, relative to supernovae, and the presence of heavy $r$-process elements, which pose significant challenges to the accurate calculation of radiative opacities and radiation transport. For example, these opacities include a dense forest of bound-bound features arising from near-neutral lanthanide and actinide elements. Here we investigate the use of fine-structure, line-binned opacities that preserve the integral of the opacity over frequency. Advantages of this area-preserving approach over the traditional expansion-opacity formalism include the ability to pre-calculate opacity tables that are independent of the type of hydrodynamic expansion and that eliminate the computational expense of calculating opacities within radiation-transport simulations. Tabular opacities are generated for all 14 lanthanides as well as a representative actinide element, uranium. We demonstrate that spectral simulations produced with the line-binned opacities agree well with results produced with the more accurate continuous Monte Carlo Sobolev approach, as well as with the commonly used expansion-opacity formalism. Additional investigations illustrate the convergence of opacity with respect to the number of included lines, and elucidate sensitivities to different atomic physics approximations, such as fully and semi-relativistic approaches.Comment: 27 pages, 22 figures. arXiv admin note: text overlap with arXiv:1702.0299

The Breakfast Food Challenge: Helping to Meet Personal Needs in the Science Classroom

One of the four Project Synthesis goal clusters for science education focuses on meeting the personal needs of students who are maturing in a scientific/technological society. Many existing science programs fall short in this regard, particularly if teachers are seriously interested in changing learner behavior for the better. One component of learner behavior that is highly consistent with the personal needs goal cluster of Project Synthesis is helping students become more intelligent consumers in a scientific society

Team Synergy in Software Inspections: A Group Behavior Analysis

Inspections provide many benefits in the software development process. However, the cost effectiveness of inspections has been criticized. Also, many organizations simply do not have the time to perform complete inspections of all software artifacts within the development schedule. Due to its pragmatic and domain-specific nature, little formal research has been performed on inspections. We propose to begin a study of software development inspections by surveying several relevant research papers on group behavior theory. We applythis research to inspections and outline a laboratory experiment for future researc

Composition Effects on Kilonova Spectra and Light Curves: I

The merger of neutron star binaries is believed to eject a wide range of heavy elements into the universe. By observing the emission from this ejecta, scientists can probe the ejecta properties (mass, velocity and composition distributions). The emission (a.k.a. kilonova) is powered by the radioactive decay of the heavy isotopes produced in the merger and this emission is reprocessed by atomic opacities to optical and infra-red wavelengths. Understanding the ejecta properties requires calculating the dependence of this emission on these opacities. The strong lines in the optical and infra-red in lanthanide opacities have been shown to significantly alter the light-curves and spectra in these wavelength bands, arguing that the emission in these wavelengths can probe the composition of this ejecta. Here we study variations in the kilonova emission by varying individual lanthanide (and the actinide uranium) concentrations in the ejecta. The broad forest of lanthanide lines makes it difficult to determine the exact fraction of individual lanthanides. Nd is an exception. Its opacities above 1 micron are higher than other lanthanides and observations of kilonovae can potentially probe increased abundances of Nd. Similarly, at early times when the ejecta is still hot (first day), the U opacity is strong in the 0.2-1 micron wavelength range and kilonova observations may also be able to constrain these abundances

Synthesis and characterization of a sol-gel derived ureasilicate hybrid organic-inorganic matrix containing CdS colloidal particles

A hybrid organic-inorganic material filled with in situ generated inorganic particles has been synthesised by the homogeneous precipitation of CdS from aqueous solutions of Cd(NO3)2 and CH3CSNH2 . These highly transparent, homogeneous and flexible CdS doped xerogels were prepared by the sol-gel technique using, as precursors, organically modified silicon alkoxide (3-isocyanatepropyltriethoxysilane) and a di-amine functionalized oligopolyoxyethylene (Jeffamine ED-600), which by subsequent hydrolysis and condensation processes formed a solid 3-D network. TEM studies indicate the presence of round nanoparticles around 20 nm in diameter dispersed in a homogeneous amorphous matrix. The samples were also characterized by spectroscopic (UV-visible and photoluminescence) and XRD techniques.Fundação para a Ciência e Tecnologia - PRAXIS/P/FIS/10128/98, SFRH / BD / 3188 / 2000

A is for Anthropocene:An A–Z of Design Ecology

This paper lists in A to Z format the changing ecology of design in the Anthropocene. From twenty-six points of view the paper contrasts design’s search for a coherent ecology – how it looks like it looks – with its search for a familiar ecology – how it is understood today. Taking each letter of the alphabet to create individual reviews of the vicissitudes of design, the paper critiques how design has historically explained to itself, and anyone who has been listening, what it has been doing, and contrasts that with what needs to be done