3,555 research outputs found

    Increasing Returns to Education and Progress towards a College Degree

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    Returns to college have increased, but graduation rates have changed relatively little. Modifying a human capital model of college enrollment to endogenize time-to-graduation, we predict that higher returns to education will both speed graduation and increase enrollment. Some of those new entrants may, however, take longer to graduate. Using the 1989 and 1995 Beginning Postsecondary Studies, we employ a multinomial logit to model the association between individual and family characteristics, and five-year college outcomes: graduation, continued enrollment, and non-enrollment. Between cohort differences arise either because the characteristics of those entering college are different or because the relations between characteristics and outcomes have changed. We utilize a Oaxaca-Blinder style decomposition to distinguish between these two alternatives, attributing differences in characteristics to newly attracted students and differences in the relations between characteristics and outcomes to historically attracted students behaving differently. It is changes in behavior that explain the increased progress we observe.Higher Education, Graduation Rates, Persistence

    Reported Progress under the Student Right-to-Know Act: How Reliable is It?

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    The Student Right-to-Know Act requires colleges to provide institution-specific information on graduation rates for students initially enrolling full-time in the fall term. Not all students enroll in that fashion, especially at two-year institutions. We use data on degree-seeking students from the 1996/2001 Beginning Post-Secondary Survey to identify students for whom statistics are and are not reportable under the Act and to track their progress. Results indicate the published progress rates are substantially higher than the progress rates for the non-reportable populations, whether students enter a two-year or a four-year institution. While progress rates for the two samples are significantly correlated within four-year institutions, they are not within two-year institutions. For those beginning at two-year institutions, the progress rates reported under the Student Right-to-Know Act are indicative of neither their absolute nor their relative (cross-institution) probability of success. Policy makers and prospective students will not make efficient decisions without better information.Efficiency, Resource Allocation, Graduation

    Paul J. Griffiths, AN APOLOGY FOR APOLOGETICS

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    The Size Relationship of 12 Days Post-Exodus Larvae with 56 Day Post-Exodus Fingerlings Regarding Growth and Survival in Bluegill (Lempomis macrochirus)

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    Low survival and quality of early life-stage bluegill is an obstacle to viable production where size may influence weaning efficiency. Herein, we investigate through two trials the effects of fry size 12-d post-exodus on total length, weight, production and survival through 56-d post-exodus. Full sibling broods (trial 1=10, trial 2=6) were reared with feedings of brine shrimp Artemia sp. nauplii (BS) through 12-d post-exodus (PE). Broods of trial 1 were visual sorted 12 d PE into small and large size groups. Fry (n = 25) from each size group were sampled for measured total length (TL) and weight. Starting 14 d PE, a 7-d co-feeding period with a commercial dry feed (#0 crumb) that was continued through 27 d PE with subsequent feedings using a larger version (#1 crumb) of the same diet continuing through 56 d PE (trial end). Broods of trial 2 were split 4 d post-conception into two gorups of pro-larvae (n = 400). Slow growing groups were fed hourly 0800-1700 while fast growing were fed additionally at 0400 and 2200 through 12 d PE. Surviving fish from each size gorup were collected, with random samples (n = 25 fish) measured for TL and weight. Fry (n = 100 where possible) were placed into 151-L aqauriums with slow and fast growing feed regimens maintained through 13-d PE. Culture regimen thereafter was same as trial 1. Fish of both trials were harvested, measured for TL, weight, and survival. The Wilcoxon Signed Rank Test was run one-tailed using SAS. Results of trial 1 indicate size at 12 d was a predictor of TL, weight and survival through 56 d PE (p ≤ 0.156). Size variation at 12 d as a function of genetics is a predictor of growth and survival through 56 d while at least some size variation resulting from early growth rate differences can be overcome by compensatory growth.https://bluetigercommons.lincolnu.edu/lucer-pubs/1007/thumbnail.jp

    Uptake of dissolved inorganic and organic bphosphorus compounds by phytoplankton and bacterioplankton

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109807/1/lno19923720232.pd

    Embryogenesis in the Dwarf Seahorse, Hippocampus zosterae (Syngnathidae)

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    Embryogenesis of the dwarf seahorse, Hippocampus zosterae, was studied by scanning electron microscopy of a series of developmental stages. Stages ranged from initial cleavage of the egg through term embryos. Embryos hatch from their egg envelopes about midway through development, yet remain nestled in stromal chambers of vascularized epithelium within the male brood pouch until their yolk reserves are consumed. The difference in body shape between the pipefish and seahorse first becomes discernible during mid-development, just before hatching. At this stage, embryos begin to develop their characteristic prehensile tail in contrast to the straight body and typical caudal fin of most species of pipefish. Post-hatching, ‘yolk-sac’ larvae have a well developed head, that is set at a right angle to the body axis, and fully formed fins. As seahorse embryos approach term, lepidotrichia calcify, and the prehensile tail is capable of muscular contraction. Dermal scutes first appear at this stage and ossify in the term embryo. The dermal armor is then fully formed and functional. At term, the yolk reserves have been depleted, and the young are released from the brood pouch as free-swimming, free-feeding miniature versions of the adults

    Daily Increment Formation in Otoliths of the Redspotted Sunfish

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    To generate reliable age information for fishes, we must assess the robustness of techniques to environmental variation. We quantified daily ring deposition within the sagittal otoliths of known-age larval and juvenile redspotted sunfish Lepomis miniatus reared in ponds. We also determined how daily light : dark cycles mimicking natural conditions, reduced daylight, or constant daylight affected ring deposition in fish housed in aquaria. Additionally, we quantified how constant temperature (26°C), low daily variability in temperature (26 ± 1°C), and high daily variability (26 ± 2°C) affected production of daily rings. In pond-reared fish, the first increment was produced by the evening of hatch, and increment deposition occurred with 24-h periodicity through 119 d. Independent age estimates from two readers closely agreed. Photocycle and temperature variation did not affect periodicity of increment formation or the precision and accuracy of age estimates. Age and growth data can be reliably determined in this species to assess recruitment dynamics and develop management and conservation strategies

    Amino Acid Profiles in the Tissues of Juvenile Bluegill (Lepomis Macrochirus) from the Wild and Commercially-fed Fish

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    Amino acid profiles of fish tissues and fish eggs have been extensively investigated in some fish species. Amino acid profiles are helpful in quantifying the indispensable amino acid requirements for these fish. Bluegill is a major forage fish for the largemouth bass (Micropterus samoides) and an important recreational fish throughout the US. The demand for bleugill as a food fish has increased recently. However, the information on the amino acid profiles of its eggs and tissues is lacking. The objectve of this study was to determine the amino acid profiles of the muscles and whole body of the 1-2 g wild and the commercially fed bluegill. Wild fish were obtained from the ponds that relied on the natural food source. Commercially fed fish were grown indoors. Skinless muscles were obtained by dissected both sides of the 1-2 g bluegill. The results showed the lysine was the most abundant indispensable amino acids in muscles and hwole body of both the wild and the farm-raised fish. The proportion of an individual indispensable amino acid to the sum of all detectable amino acids amount was similar for whole body and muscles in wild or raised fish. For whole body or muscle tissue, wild fish contained significantly higher crude protein but lower crude lipid levels than farm-raised bluegill (p\u3c0.05). This study suggested that nutritional history affected tissue proximate compositions.https://bluetigercommons.lincolnu.edu/lucer-pubs/1003/thumbnail.jp

    A Predicted Correlation Between Age Gradient and Star Formation History in FIRE Dwarf Galaxies

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    We explore the radial variation of star formation histories in dwarf galaxies simulated with Feedback In Realistic Environments (FIRE) physics. The sample contains 9 low-mass field dwarfs with M_ star = 10^5 - 10^7 M_sun from previous FIRE results, and a new suite of 17 higher mass field dwarfs with M_star = 10^7 - 10^9 M_sun introduced here. We find that age gradients are common in our dwarfs, with older stars dominant at large radii. The strength of the gradient correlates with overall galaxy age such that earlier star formation produces a more pronounced gradient. The relation between formation time and strength of the gradient is driven by both mergers and star-formation feedback. Mergers can both steepen and flatten the age gradient depending on the timing of the merger and star formation history of the merging galaxy. In galaxies without significant mergers, early feedback pushes stars to the outskirts at early times. Interestingly, among galaxies without mergers, those with large dark matter cores have flatter age gradients because these galaxies have more late-time feedback. If real galaxies have age gradients as we predict, stellar population studies that rely on sampling a limited fraction of a galaxy can give a biased view of its global star formation history. We show that central fields can be biased young by a few Gyrs while outer fields are biased old. Fields positioned near the 2D half-light radius will provide the least biased measure of a dwarf galaxy's global star formation history.Comment: 13 pages, 8 figures. Submitted to MNRAS, comments welcom
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