Leaf Processing in a Slough of an Ozark Stream

Processing of sugar maple (Acer saccharum), black oak (Quercus velutina), and American sycamore (Platanus occidentalis) was investigated in a slough of the Illinois River, Benton County, Arkansas, using 5-gram packs in wire baskets. Oak and sycamore showed similar degradation rates, while maple was processed much faster. All processing rates were strongly retarded during a period of siltation. Chironomid larvae were the dominant organisms associated with the packs and their numbers were depressed by the silt influx. Shredders were notably few in number as compared with studies from the northwestern United States

Inverse Geometry for Stereolithographic Manufacturing

As parts produced by stereolithography form and cure, they warp and shrink to produce Pitrts that are not quite the san~ ~ as those originally specified. This research attempts to solve the inverse geomptry problem, that is, what shape should be specified initially so that the she pe produced is the desired one. Assuming that 'the process is repeatable, we ~neasure the difference between the ideal and actua). part dimensions. A finite-element based model is built which mirrors the distortion from the ideal geometry. A "pre-deformed" geometry is then built so that it deforms to the ideal geometry under the conditions imposed on the finite element model. This pre-warped geometry is the geometry we seek.Mechanical Engineerin

Stability of the two-phase microstructure of shocked zirconium

The microstructure of two-phase () shocked zirconium was studied in-situ during heating with high energy X-ray diffraction techniques. The volume fraction of the phase was monitored as the reverse phase transformation occurred:metastable the start and finish temperatures being 470 K and 550 K, respectively, during heating at 3 K/min. Phase strains were monitored and separated in terms of thermal expansion and mechanical strains due to local phase constraints. Stresses in the zirconium were estimated to be a superposition of a hydrostatic component (of order –50 MPa) and uniaxial component (of order –600 MPa) along the c-axis. A high dislocation density was observed in both the phases in the as-shocked state. The dislocation and phasedensity of the decreased preceding the reverse transformation suggesting that it is the presence of the high concentration of defects in the phase which retarded the preverse transformation to the stable hase

Color-Magnitude Diagram Constraints on the Metallicities, Ages, and Star Formation History of the Stellar Populations in the Carina Dwarf Spheroidal Galaxy

Victoria-Regina isochrones for $-0.4 \le$ [alpha/Fe] $\le +0.4$ and a wide range in [Fe/H], along with complementary zero-age horizontal branch (ZAHB) loci, have been applied to the color-magnitude diagram (CMD) of Carina. The color transformations that we have used have been "calibrated" so that isochrones provide excellent fits to the $[(B-V)_0,\,M_V]$-diagrams of M3 and M92, when well supported estimates of the globular cluster (GC) reddenings and metallicities are assumed. The adopted distance moduli, for both the GCs and Carina, are based on our ZAHB models, which are able to reproduce the old HB component (as well as the luminosity of the HB clump) of the dwarf spheroidal galaxy quite well --- even if it spans a range in [Fe/H] of ~ 1.5 dex, provided that [alpha/Fe] varies with [Fe/H] in approximately the way that has been derived spectroscopically. Ages derived here agree reasonably well with those found previously for the old and intermediate-age turnoff stars, as well as for the period of negligible star formation (SF) activity (~ 6-10 Gyr ago). CMD simulations have been carried out for the faintest turnoff and subgiant stars. They indicate a clear preference for SF that lasted several Gyr instead of a short burst, with some indication that ages decrease with increasing [Fe/H]. In general, stellar models that assume spectroscopic metallicities provide satisfactory fits to the observations, including the thin giant branch of Carina, though higher oxygen abundances than those implied by the adopted values of [alpha/Fe] would have favorable consequences.Comment: 15 pages, including 12 figures; accepted for publication in the Astrophysical Journa

is Social Security Part of the Social Safety Net?

Building on the existing literature that examines the extent of redistribution in the Social Security system as a whole, this paper focuses more specifically on how Social Security affects the poor. This question is important because a Social Security program that reduces overall inequality by redistributing from high income individuals to middle income individuals may do nothing to help the poor; conversely, a program that redistributes to the poor may nonetheless be regressive according to broader measures if it also redistributes from middle to upper income households. We have four major findings. First, as we expand the definition of income to use more comprehensive measures of well-being, we find that Social Security becomes less progressive. Indeed, when we use an "endowment" defined by potential labor earnings at the household level, rather than actual earnings at the individual level, we find that Social Security has virtually no effect on overall inequality. Second, we find that this result is driven largely by the lack of redistribution across the middle and upper part of the income distribution, so it masks some small positive net transfers to those at the bottom of the lifetime income distribution. Third, in cases where redistribution does occur, we find it is not efficiently targeted: many high income households receive positive net transfers, while many low income households pay net taxes. Finally, the redistributive effects of Social Security change over time, and these changes depend on the income concept used to classify someone as "poor".

Impact of Student Teaching On the Mathematics Teaching Efficacy Beliefs of Preservice Elementary Teachers

Much attention, both nationally and internationally, has been given to mathematics teaching and student mathematical performance (e.g. No Child Left Behind Act (2001), National Council of Teachers of Mathematics (1991, 2000) standards, Common Core State Standards Initiative, Trend in International Mathematics and Science Study (2013), and Program of International Student Assessment PISA (2013)). Teachers of mathematics have come under greater scrutiny and demands for student success have been placed upon them. Research has shown that teacher efficacy and mathematics teaching efficacy, forms of self-efficacy beliefs (Bandura, 1977, 1997), can have a positive impact on teaching and learning. Yet, there has been limited research on the mathematics teacher efficacy of preservice elementary teachers (Swars, 2005). This study examined the impact of the student teaching experience on the mathematics teaching efficacy beliefs of preservice elementary teachers. What happens to the level of mathematics teaching efficacy beliefs of preservice teachers during the student teaching experience? What are the characteristics of preservice teachers with low and high levels of efficacy beliefs? What factors from the student teaching experience influenced efficacy beliefs? A qualitative case study (Merriam, 2009) with an embedded survey was used to address the previous questions. The results of this study demonstrate that mathematics teaching efficacy beliefs of preservice teachers rose significantly during the student teaching experience. However, the change was not uniform. Personal mathematics teaching efficacy (PMTE) increased significantly. Although mathematics teaching outcome expectancy (MTOE) increased, it was not significant. Furthermore, the research indicates four characteristics influenced mathematics teaching efficacy beliefs: attitude toward mathematics, use of manipulatives, motivation to teach, and persistence. Four factors appear to impact the development of efficacy beliefs of preservice teachers: prior experiment with mathematics, student teaching experience, relationship with cooperating teacher, and students served by the preservice teachers