San Diego State University

About: San Diego State University is a education organization based out in San Diego, California, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 12418 authors who have published 27950 publications receiving 1192375 citations. The organization is also known as: SDSU & San Diego State College.

Kepler Mission Stellar and Instrument Noise Properties

Abstract: Kepler mission results are rapidly contributing to fundamentally new discoveries in both the exoplanet and asteroseismology fields. The data returned from Kepler are unique in terms of the number of stars observed, precision of photometry for time series observations, and the temporal extent of high duty cycle observations. As the first mission to provide extensive time series measurements on thousands of stars over months to years at a level hitherto possible only for the Sun, the results from Kepler will vastly increase our knowledge of stellar variability for quiet solar-type stars. Here, we report on the stellar noise inferred on the timescale of a few hours of most interest for detection of exoplanets via transits. By design the data from moderately bright Kepler stars are expected to have roughly comparable levels of noise intrinsic to the stars and arising from a combination of fundamental limitations such as Poisson statistics and any instrument noise. The noise levels attained by Kepler on-orbit exceed by some 50% the target levels for solar-type, quiet stars. We provide a decomposition of observed noise for an ensemble of 12th magnitude stars arising from fundamental terms (Poisson and readout noise), added noise due to the instrument and that intrinsic to the stars. The largest factor in the modestly higher than anticipated noise follows from intrinsic stellar noise. We show that using stellar parameters from galactic stellar synthesis models, and projections to stellar rotation, activity, and hence noise levels reproduce the primary intrinsic stellar noise features.

Worlds of written discourse: a genre-based view

Abstract: WORLDS OF WRITTEN DISCOURSE: A GENRE-BASED VIEW. Vijay K. Bhatia. New York: Continuum, 2004. Pp. xvii + 228. $49.95 paper.In this volume, Bhatia discusses multiple aspects of written discourse as produced in the real world by focusing not just on academic genres but on genres from professional and institutional contexts as well. His consideration of disciplinary variation in genres, relationships across genres, appropriation of generic resources as seen in hybrid genres, and the nature of generic integrity has led to an extension of genre theory not “constrained by the nature and design of its applications” (p. xiv) that is discussed here. In addition to this development of genre theory, this well-crafted volume provides a multiperspective, multidimensional model of genre analysis.

Complex Sentence Comprehension and Working Memory in Children With Specific Language Impairment

Abstract: Purpose This study investigated the association of 2 mechanisms of working memory (phonological short-term memory [PSTM], attentional resource capacity/allocation) with the sentence comprehension of school-age children with specific language impairment (SLI) and 2 groups of control children. Method Twenty-four children with SLI, 18 age-matched (CA) children, and 16 language- and memory-matched (LMM) children completed a nonword repetition task (PSTM), the competing language processing task (CLPT; resource capacity/allocation), and a sentence comprehension task comprising complex and simple sentences. Results (1) The SLI group performed worse than the CA group on each memory task; (2) all 3 groups showed comparable simple sentence comprehension, but for complex sentences, the SLI and LMM groups performed worse than the CA group; (3) for the SLI group, (a) CLPT correlated with complex sentence comprehension, and (b) nonword repetition correlated with simple sentence comprehension; (4) for CA children, neith...

Primary productivity and its regulation in the equatorial Pacific during and following the 1991–1992 El Niño

Abstract: The cycling of carbon in the equatorial Pacific Ocean was investigated by the Equatorial Pacific (EqPac) Study in 1992. As part of that study in situ primary productivity was measured on survey and time-series cruises along 140°W from 12°N to 12°S with methods determined to be trace-metal clean. Primary productivity, chlorophyll and chlorophyll-specific productivity rates varied coherently in relation to two large-scale features: temporally, primary productivity was reduced during the El Nino dominated period (February–April 1992) and increased during the cool period (August–October 1992); and spatially enhanced primary productivity persisted close to the equator relative to the oligotrophic regions poleward of 10°N and 10°S. On the equator in October 1992 during the period of relatively cool water, primary productivity was about twice (125 mmol C m−2 day−1) the value during the peak warm period (60 mmol C m−2 day−1). The climatological mean equatorial productivity in the cold tongue has been recalculated to be about 75 mmol C m−2 day−1 (Chavez et al., 1996). The mean 1992 productivity on the equator (1°S–1°N) was about 25% higher than climatology (95 vs 75 mmol Cm−2 day−1) and about 3 times the value in oligotrophic waters poleward of 10°N and 10°S (95 vs 30 mmol C m−2 day−1). Higher chlorophyll-specific productivity during the cool period relative to the warm period (3.9 vs 2.4 mmol C mg chl−1 day−1) indicates that the increase in absolute productivity did not result solely from a biomass increase, but from a change in the nutrient-regulated specific productivity rate. The regulating nutrient was not a macronutrient, such as nitrate or silicic acid, because macronutrients (and light) were present in uptake-saturating concentrations during both the warm and cool periods of the 1992 EqPac study. Physiological constraint by a micronutrient, such as iron, is implicated as the factor regulating these productivity variations. The change in iron supply resulted from a change in equatorial circulation processes. During the warm period, El Nino-Southern Oscillation (ENSO)-driven changes in pycnocline topography depressed the Equatorial Undercurrent (EUC), thereby decreasing the amount of iron-rich EUC water entrained into equatorial upwelling and vice versa during the cool period. During the August–October cool period of generally increased productivity, two further episodic increases in specific productivity, biomass and diatom abundance occurred during intense and remotely forced upwelling events associated with a front or the passage of a frontal wave. In both mesoscale episodes, temperature and salinity show that the intensified upwelling reached more deeply into the already relatively shallow EUC. Productivity and biomass increases during both of these events were quantitatively similar to those in an in situ iron addition experiment (IronEx) carried out in equatorial Pacific waters in 1993. Variations in the supply of upwelled iron provided by the iron-rich EUC best account for the warm-cool period difference in phytoplankton productivity as well as the episodic increases in specific productivity, biomass and diatom abundance during intense mesoscale upwelling events seen in the dynamic equatorial region in the EqPac study.