LSST: from Science Drivers to Reference Design and Anticipated Data Products

(Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg$^2$ field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5$\sigma$ point-source depth in a single visit in $r$ will be $\sim 24.5$ (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg$^2$ with $\delta<+34.5^\circ$, and will be imaged multiple times in six bands, $ugrizy$, covering the wavelength range 320--1050 nm. About 90\% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg$^2$ region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to $r\sim27.5$. The remaining 10\% of the observing time will be allocated to projects such as a Very Deep and Fast time domain survey. The goal is to make LSST data products, including a relational database of about 32 trillion observations of 40 billion objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures available from https://www.lsst.org/overvie

Ecophysiological response of Sorghum halepense populations to reduced rates of nicosulfuron Resposta ecofisiológica de populações de Sorghum halepense a doses reduzidas de nicosulfuron

The control and regrowth after nicosulfuron reduced rate treatment of Johnsongrass (Sorghum halepense L. Pers.) populations, from seven Argentinean locations, were evaluated in pot experiments to assess if differential performance could limit the design and implementation of integrated weed management programs. Populations from humid regions registered a higher sensibility to reduced rates of nicosulfuron than populations from subhumid regions. This effect was visualised in the values of regression coefficient of the non-linear models (relating fresh weight to nicosulfuron rate), and in the time needed to obtain a 50% reduction of photosynthesis rate and stomatal conductance. The least leaf CO2 exchange of subhumid populations could result in a lower foliar absorption and translocation of nicosulfuron, thus producing less control and increasing their ability to sprout and produce new aerial biomass. The three populations from subhumid regions, with less sensibility to nicosulfuron rates, presented substantial difference in fresh weight, total rhizome length and number of rhizome nodes, when they were evaluated 20 week after treatment. In consequence, a substantial Johnsongrass re-infestation could occur, if rates below one-half of nicosulfuron labeled rate were used to control Johnsongrass in subhumid regions.<br>Foram conduzidos experimentos sob condições controladas, a fim de se investigar os efeitos de doses reduzidas de nicosulfuron, no controle e rebrota de populações de capim massambará (Sorghum halepense), de sete localidades da Argentina, visando programas de manejo integrado. As populações das regiões úmidas registraram maior sensibilidade a doses reduzidas de nicosulfuron, em relação àquelas das regiões subúmidas. Esse efeito foi observado nos valores do coeficiente de regressão, das curvas de dose-resposta de modelo log-logístico, que relacionam a biomassa fresca com doses de nicosulfuron; tal efeito foi observado também no tempo necessário para se obter 50% da redução da fotossíntese e da condutância estomática. O menor intercâmbio de CO2, obtido nessas populações subúmidas, pode ter contribuído para a absorção e translocação mais baixa do nicosulfuron, tendo produzido menor controle e, conseqüentemente, tendo aumentado sua capacidade de rebrotar e produzir nova biomassa aérea ao final do ciclo. As três populações das regiões subúmidas, com menor sensibilidade ao nicosulfuron, apresentaram uma diferença substancial na biomassa fresca, no comprimento total e no número de nódulos dos rizomas, quando foram avaliadas vinte semanas após o tratamento com herbicida. Os resultados obtidos sugerem que se forem usadas doses de nicosulfuron menores do que as recomendadas, pode ocorrer uma severa rebrota do capim massambará em regiões subúmidas

Between Education and Propaganda: Public Controversy Over Presidential Library Design

While there is abundant scholarship on extant presidential libraries, rejected presidential library proposals are comparatively understudied. Here, we analyze the public controversies surrounding Richard Nixon's and Ronald Reagan's ill-fated plans for housing their presidential libraries at Duke and Stanford Universities, respectively. These parallel cases offer a glimpse into what Thomas Farrell terms “social knowledge in controversy” — episodes where prevailing social precedents governing human decision-making evolve in the crucible of public argument. What are the presumptions about how presidential libraries should be built and operated? How did they shape the public argument at Duke and Stanford during the early 1980s, and in turn, how did those schools' ultimate decisions to reject the Nixon and Reagan Library proposals reinforce or mold the presumptions? Through examination of primary documents housed at the Stanford and Duke University archives, we generate insight regarding the evolving political function of presidential libraries, and explore the utility of Chaïm Perelman and Lucie Olbrechts-Tyteca's theory of argumentation as a tool of rhetorical criticism. Such inquiry is especially timely in the contemporary milieu, where public controversy simmers regarding the 43rd American president's future library at Southern Methodist University, and where issues of government transparency and accountability persist as salient topics of public and scholarly concern