7,445 research outputs found
Development of anion-selective membranes
Methods were studied of preparing anion-exchange membranes that would have low resistance, high selectivity, and physical and chemical stability when used in acidic media in a redox energy storage system. Of the twelve systems selected for study, only the system that was based on crosslinked poly-4-vinylpyridinium chloride produced physically strong membranes when equilibrated in l M HCl. The resistivity of the best membrane was 12 ohm-cm, and the transference number for chloride ions was 0.81
Infusible silazane polymer and process for producing same
Coatings of high thermal and chemical stability for application to metal, glass, ceramics, and other surfaces are formed by reacting diphenyldichlorosilane in the presence of triethylamine with a nitrogen base selected from the group consisting of ammonia and methylamine. The pl polymeric, noncrystalline reaction product is heated in a reaction zone open to the atmosphere at a temperature ranging from approximately 250 C to 450 C until the infusible polymer is formed
The status of music education in the public junior high schools of Massachusetts as of the year 1945-1955
Thesis (Ed.M.)--Boston Universit
The Static Dielectric Constant of a Colloidal Suspension
We derive an expression for the static dielectric constant of the colloidal
susp ensions based on the electrokinetic equations. The analysis assumes that
the ions have the same diffusivity, and that the double layer is much thinner
than the radius of curvature of the particles. It is shown that the dielectric
increment of the double layer polarization mechanism is originated from the
free energy stored in the salt concentration inhomogeniety. We also show that
the dominant polarization charges in the theory are at the electrodes, rather
than close to the particles.Comment: 15 pages, 1 figur
Assessment of Restoration Seedings on Utah Watershed Restoration Initiative Project Sites
Overabundance of shrubs poses a major threat to semiarid ecosystems due to degraded understory vegetation. Previous efforts suggest a need for greater understanding of which management practices work best to improve these ecosystems. I sought to develop a better understanding of how the relative performance of commonly seeded species is influenced by three sagebrush removal techniques.
I calculated effect sizes for cover and frequency to estimate relative changes in abundance of 15 common plant species seeded at 63 restoration sites throughout Utah. Shrubs were reduced by fire or mechanical treatment. Effect sizes were assessed using meta-analysis techniques for two post-treatment timeframes. Introduced grasses and shrubs had greater increases in cover and frequency following treatment, respectively. The introduced shrub Bassia prostrata experienced the largest increases in abundance following treatments. Forb abundance was highest when treated with fire. Over the long term the fire treatment resulted in greater increases for four of the seven grass species. Large increases in perennial grasses over time suggest that seeding efforts contributed to enhancing understory herbaceous conditions. My results provide new insights regarding the interactive effects of species and shrub-reduction treatments.
Secondly, I evaluated emergence patterns of six commonly seeded restoration species in soils collected from Wyoming big sagebrush (A. t. ssp. wyomingensis [Beetle & A. Young] S.L. Welsh) and mountain big sagebrush (A. t. ssp. vaseyana [Rydb.] Beetle) plant communities. I developed a novel experimental design that regularly wetted soils to field capacity and allowed them to naturally dry by evaporation, which resulted in distinct differences in the duration of wet-dry cycles. Results showed that inherent differences in soil texture and organic matter between vaseyana and wyomingensis soils translated into fundamental differences in soil water holding capacity. Although species collectively exhibited greater emergence in vaseyana soils than wyomingensis soil, patterns were vastly different among species and differences between soils became more pronounced under low soil water for two of the test species. I concluded that the manner in which soils and water uniquely influenced emergence patterns provide new insights in species suitability for restoration sites and how inherent soil differences may constrain seeding success
Narrative and the Maintenance of Great Lakes Native American Cultural Identity
This paper examines the relationship of the trickster character to the maintenance of Great Lakes Native American cultural identity by using interviews and literary analysis. The interviews gathered statements from participants about their personal experiences with narrative, and the social context of narrative, within their tribes. The literary analysis examines three stories in the Manabozho cycle: The theft of fire, Manabozho and wolf, and The flood. The themese in these stories fulfill all four of William Bascom\u27s four functions folklore. The hypothesis that narrative is a necessary factor of cultural maintenance has been supported by both the interviews and the literary analysis
Effects of Static, Countermovement, and Drop Jump Performance on Power and Rate of Force Development in 6 - 16 Year Old Boys
The purpose of this study was to examine the effects of static, counter movement, and drop jump performance on peak power and peak rate of force development (RFD). The secondary purpose of this study was to examine the relationship between vertical jump outcomes, maturity offset, and muscle cress-sectional area (CSA). During a single testing session, twenty-one young males (mean age ± SD = 12.1 ± 2.4 yrs) performed maximal vertical jumps which included: static jump (SJ), counter movement jump (CMJ), and drop jump from 8 (DJ8), 12 (DJ12) and 16 (DJ16) inches in a randomized order. Peak power increased from SJ to CMJ (p ≤ 0.001) but showed no subsequent increases among CMJ, DJ8, DJ12, or DJ16. RFD and force showed no increase from SJ to CMJ (p \u3e 0.05), an increase from CMJ to DJ8 (p ≤ 0.001), but no further increases from DJ8 to DJ12 to DJ16 (p \u3e 0.05). Eccentric impulse increased systematically from SJ to DJ16 (p ≤ 0.001). Concentric impulse increased from SJ to CMJ (p ≤ 0.001), decreased from CMJ to DJ8 (p = 0.003), then showed no change from DJ8 to DJ12 to DJ16 (p \u3e 0.05). Stepwise regression indicated that the increase in power from SJ to CMJ was best explained by height (R2 = 0.517). These findings suggest CMJ is the optimal jump test for maximizing peak power and concentric work, while minimizing eccentric overload in male of a similar age to this study. Additionally, growth and development may influence stretch-shortening cycle (SSC) utilization. Future studies are needed to examine the influence of PHV maturity offset and increased muscle CSA on SSC utilization in this model of incremental eccentric pre-loading during vertical jump tests.
Advisor: Joel T. Crame
Southern Arizona riparian habitat: Spatial distribution and analysis
The objectives of this study were centered around the demonstration of remote sensing as an inventory tool and researching the multiple uses of riparian vegetation. Specific study objectives were to: (1) map riparian vegetation along the Gila River, San Simon Creek, San Pedro River, Pantano Wash, (2) determine the feasibility of automated mapping using LANDSAT-1 computer compatible tapes, (3) locate and summarize existing mpas delineating riparian vegetation, (4) summarize data relevant to Southern Arizona's riparian products and uses, (5) document recent riparian vegetation changes along a selected portion of the San Pedro River, (6) summarize historical changes in composition and distribution of riparian vegetation, and (7) summarize sources of available photography pertinent to Southern Arizona
Conditional Mass Functions and Merger Rates of Dark Matter Halos in the Ellipsoidal Collapse Model
Analytic models based on spherical and ellipsoidal gravitational collapse
have been used to derive the mass functions of dark matter halos and their
progenitors (the conditional mass function). The ellipsoidal model generally
provides a better match to simulation results, but there has been no simple
analytic expression in this model for the conditional mass function that is
accurate for small time steps, a limit that is important for generating halo
merger trees and computing halo merger rates. We remedy the situation by
deriving accurate analytic formulae for the first-crossing distribution, the
conditional mass function, and the halo merger rate in the ellipsoidal collapse
model in the limit of small look-back times. We show that our formulae provide
a closer match to the Millennium simulation results than those in the spherical
collapse model and the ellipsoidal model of Sheth & Tormen (2002).Comment: 5 pages, 3 figures, accepted by MNRAS letter
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