16,641 research outputs found
The K Band Luminosity Functions of Galaxies in High Redshift Clusters
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
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?
This study examined whether providing preschool children with simple groundrules (the importance of being complete, saying „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
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
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
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
Correspondence related to Wyatt Sawyer\u27s book, Must the Young Die, Too
Letter from Alonzo Ellis Jones to Wyatt Sawyer [No date]
Correspondence related to Wyatt Sawyer\u27s book, Must the Young Die, Too
Letter from Alonzo Ellis Jones to Mrs. West May 10, 1946
Correspondence related to Wyatt Sawyer\u27s book, Must the Young Die, Too
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