16,641 research outputs found

    The K Band Luminosity Functions of Galaxies in High Redshift Clusters

    Full text link
    K band luminosity functions (LFs) of three, massive, high redshift clusters of galaxies are presented. The evolution of K*, the characteristic magnitude of the LF, is consistent with purely passive evolution, and a redshift of forma tion z = 1.5-2.Comment: 3 pages, to appear in Proceedings of IAU Colloquium 195 - Outskirts of Galaxy Clusters: intense life in the suburb

    Keck Spectroscopy of Faint 3 < z < 7 Lyman Break Galaxies: III. The Mean Ultraviolet Spectrum at z=4

    Get PDF
    We present and discuss the mean rest-frame ultraviolet spectrum for a sample of 81 Lyman Break Galaxies (LBGs) selected to be B-band dropouts with a mean redshift of z=3.9 and apparent magnitudes z_AB<26. Most of the individual spectra are drawn from our ongoing survey in the GOODS fields with the Keck DEIMOS spectrograph, and we have augmented our sample with published data taken with FORS2 on the VLT. In general we find similar trends in the spectral diagnostics to those found in the earlier, more extensive survey of LBGs at z=3 undertaken by Shapley et al (2003). Specifically, we find low-ionization absorption lines which trace the presence of neutral outflowing gas are weaker in galaxies with stronger Lyman-alpha emission, bluer UV spectral slopes, lower stellar masses, lower UV luminosities and smaller half-light radii. This is consistent with a physical picture whereby star formation drives outflows of neutral gas which scatters Lyman-alpha and gives rise to strong low-ionization absorption lines, while increasing the stellar mass, size, metallicity, and dust content of galaxies. Typical galaxies are thus expected to have stronger Lyman-alpha emission and weaker low-ionization absorption at earlier times (higher redshifts). Indeed, our mean spectrum at z=4 shows somewhat weaker low-ionization absorption lines than at z=3 and available data at higher redshift indicates a rapid decrease in low-ionization absorption strength with redshift. We argue that the reduced low-ionization absorption is likely caused by a decrease in the covering fraction and/or velocity range of outflowing neutral gas at earlier epochs. Our continuing survey will enable us to extend these diagnostics more reliably to higher redshift and determine the implications for the escape fraction of ionizing photons which governs the role of early galaxies in cosmic reionization. [Abridged]Comment: 17 pages, 12 figures, submitted to ApJ. Comments welcom

    Do simple "groundrules" reduce preschoolers\u27 suggestibility about experienced and nonexperienced events?

    Full text link
    This study examined whether providing preschool children with simple groundrules (the importance of being complete, saying &bdquo;I don‟t know‟, correcting the interviewer and not guessing) would reduce false details in their recall of a staged event. Forty-nine preschool children participated in an event that consisted of two activities. One or two days later they were given a biasing interview that included false suggestions about one of the experienced activities as well as a non-experienced activity. For the other activity, no suggestions were made. Eight, 15, and 22 days after the event, the children were required to recall all three activities in their own words. Immediately prior to their recall, half of the children were provided with the groundrules while the remaining children were not. The children in the control group also participated in a fifth interview in which they received the groundrule instructions. The results revealed that the provision of the groundrules had negligible impact on the accuracy of information provided irrespective of the context or order of the interview or the activity being recalled. The implications of these results are discussed and suggestions for future research are offered.<br /

    Grammatical Morphology in School-Age Children With and Without Language Impairment: A Discriminant Function Analysis

    Get PDF
    Purpose: The purpose of this study was to test Bedore and Leonard\u27s (1998) proposal that a verb morpheme composite may hold promise as a clinical marker for specific language impairment (SLI) in English speakers and serve as an accurate basis for the classification of children with and without SLI beyond the preschool level. Method: The language transcripts of 50 school-age children with SLI (Mage = 7;9 [years;months]) and 50 age-matched typically developing peers (Mage = 7;9) were analyzed. Following the Bedore and Leonard (1998) procedure, 3 variables were measured: a finite verb morpheme composite, a noun morpheme composite, and mean length of utterance in morphemes (MLUm). Results: Overall findings indicated that neither grammatical morpheme composite alone adequately discriminated the groups at this developmental level. However, combining the verb and noun grammatical morpheme composite measures with MLUm resulted in good discriminant accuracy in classifying subgroups of the youngest children with and without SLI in the school-age sample. Conclusion: Verb morphology alone is not a useful clinical marker of SLI in school-age children. Potential explanations for these findings and ideas for future research are discussed

    Grammatical Morphology in School-Age Children With and Without Language Impairment: A Discriminant Function Analysis

    Get PDF
    Purpose: The purpose of this study was to test Bedore and Leonard\u27s (1998) proposal that a verb morpheme composite may hold promise as a clinical marker for specific language impairment (SLI) in English speakers and serve as an accurate basis for the classification of children with and without SLI beyond the preschool level. Method: The language transcripts of 50 school-age children with SLI (Mage = 7;9 [years;months]) and 50 age-matched typically developing peers (Mage = 7;9) were analyzed. Following the Bedore and Leonard (1998) procedure, 3 variables were measured: a finite verb morpheme composite, a noun morpheme composite, and mean length of utterance in morphemes (MLUm). Results: Overall findings indicated that neither grammatical morpheme composite alone adequately discriminated the groups at this developmental level. However, combining the verb and noun grammatical morpheme composite measures with MLUm resulted in good discriminant accuracy in classifying subgroups of the youngest children with and without SLI in the school-age sample. Conclusion: Verb morphology alone is not a useful clinical marker of SLI in school-age children. Potential explanations for these findings and ideas for future research are discussed

    Multi-fuel rotary engine for general aviation aircraft

    Get PDF
    Design studies of advanced multifuel general aviation and commuter aircraft rotary stratified charge engines are summarized. Conceptual design studies were performed at two levels of technology, on advanced general aviation engines sized to provide 186/250 shaft kW/hp under cruise conditions at 7620 (25000 m/ft) altitude. A follow on study extended the results to larger (2500 hp max.) engine sizes suitable for applications such as commuter transports and helicopters. The study engine designs were derived from relevant engine development background including both prior and recent engine test results using direct injected unthrottled rotary engine technology. Aircraft studies, using these resultant growth engines, define anticipated system effects of the performance and power density improvements for both single engine and twin engine airplanes. The calculated results indicate superior system performance and 27 to 33 percent fuel economy improvement for the rotary engine airplanes as compared to equivalent airframe concept designs with current baseline engines. The research and technology activities required to attain the projected engine performance levels are also discussed

    Letter from Alonzo Ellis Jones to Mrs. West February 28, 1946

    Get PDF
    Correspondence related to Wyatt Sawyer\u27s book, Must the Young Die, Too

    Letter from Alonzo Ellis Jones to Wyatt Sawyer [No date]

    Get PDF
    Correspondence related to Wyatt Sawyer\u27s book, Must the Young Die, Too

    Letter from Alonzo Ellis Jones to Mrs. West May 10, 1946

    Get PDF
    Correspondence related to Wyatt Sawyer\u27s book, Must the Young Die, Too
    • …
    corecore