Isomer effects on polyimide properties

Polyimide polymers which are thermally stable and processable are developed. The addition of alkyl substituents to an aromatic ring in the polymer backbone is examined along with polyimide precursor amines containing functional groups that allow for post-cure crosslinking. The synthesis of key monomers is reported, including 2,4,6-tris (m-aminobenzyl) 1,3,5-trimethyl benzene and 2,4,6-tris (p-aminobenzyl) 1,3,5-trimethyl benzene. The preparation of a key monomer, 2,5,3-triamino benzophenone, is reported

More Efficient High Schools in Maine: Emerging Student-Centered Learning Communities

American K-12 public education all across the nation is at a difficult and critical crossroads. We are at a time when keen global competition underscores the need for exceptional performance in our primary and secondary schools. Yet, state and federal governments face unprecedented budget deficits and limited resources for the foreseeable future. Additionally, our schools are being called upon to do an even better job of preparing students for the 21st century. There is growing evidence that success in the 21st Century requires more than what has traditionally been the content of schooling. It requires more and different types of knowledge, skills, and learning. To help students acquire this knowledge base and skills, many educators and leaders are calling for transformative changes in our schools and changes in how we help students learn. This transformative change is called by many names: performance-based learning, standards-based learning, and student-centered learning. The Nellie Mae Education Foundation (NMEF) describes this transformation to more student-centered learning as the need for:... growing a greater variety of higher quality educational opportunities that enable all learners -- especially and essentially underserved learners -- to obtain the skills, knowledge and supports necessary to become civically engaged, economically self-sufficient lifelong learners. (2011) Can our schools be transformed to meet these challenges? More importantly, can they be high performing, efficient, and student-centered at the same time? To explore these questions, the Center for Education Policy, Applied Research, and Evaluation at the University of Southern Maine conducted a study in 2010-2011 of a sample of Maine high schools. Funded in part by the Nellie Mae Education Foundation, the study examined the degree to which these More Efficient high schools were also student-centered. In 2010, NMEF identified some of the key principles and attributes of studentcentered learning. The principles are that: Student-centered education systems provide all students equal access to the skills and knowledge needed for college and career readiness in today's world. Student-centered education systems align with current research on the learning process and motivation. Student-centered education systems focus on mastery of skills and knowledge. Student-centered education systems build student's identities through a positive culture with a foundation of strong relationships and high expectations. Student-centered education systems empower and support parents, teachers, administrators, and other community members to encourage and guide learners through their educational journey. The key attributes are that: Curriculum, instruction and assessment embrace the skills and knowledge needed for success. Community assets are harnessed to support and deepen learning experiences. Time is used flexibly and includes learning opportunities outside the traditional school day and year. Mastery-based strategies are employed to allow for pacing based on proficiency in skills and knowledge. The goal of the study reported here was to determine to what extent these principles and attributes may be found in the high schools. To that end, once a sample of More Efficient high schools was identified, the beliefs, strategies, and practices found in these schools were examined in light of the 2010 NMEF key principles and attributes

Isomer effects on polyimide properties

The effect of structure variation on the solubility and glass-transition temperature of polyimide polymers is investigated. The addition of alkyl substituents to an aromatic ring in the polymer molecule, the reduction in the number of imide rings per average polymer chain-length, and a variation in the symmetry of the polymer molecule are studied. The synthesis of key intermediates for the preparation of the monomers required in this investigation is reported along with progress made in the synthesis of polyimide-precursor amines that contain functional groups to allow for post-cure cross-linking

Germination, emergence, and seed persistence of Panicum miliaceum L.

1984 Summer.Includes bibliographical references (pages 110-115).The effects of varying levels of temperature, moisture, and seed depth on wild proso millet (Panicum miliaceum L.) emergence were observed. The effects of depth and duration of seed burial and the effects of seed overwintering on the soil surface on modes of seed depletion and persistence were studied. Patterns of wild proso millet emergence in the field were studied under conditions of plus or minus intraspecific and corn competition, and with and without soil disturbance. Emergence occurred over a range of 10 to 40 C with percent and speed of emergence increasing with temperature. Under simulated drought conditions induced by polyethylene glycol, germination was reduced at both temperatures tested (25, 30 C) as moisture stress increased. The greatest moisture stress that germination occurred at was -14 bars (1 .5%) at 30 C and -10 bars (2%) at 25 C. Germination at 30 C was higher at all moisture levels than at 25 C. Emergence from soil moisture levels of 35 to 100% field capacity was greater than 87%. Emergence ceased below 25% field capacity. Fluctuations of soil moisture resulted in slightly higher emergence than at a constant soil moisture level. Emergence was equal from 1 to 8 cm of seed depth with 14 cm the maximum depth of emergence. After 21 months of seed burial loss was greatest at 5 cm, with only 23% viable seed remaining. Persistence increased with soil depth with 77 and 93% viable seed at 10 and 30 cm, respectively. The main mode of depletion was in situ germination which decreased with depth. Seed death was not a major factor of depletion and was not affected by depth. The majority of depletion occurred within the first 12 months with seed populations stabilizing from 12 to 21 months of burial. Seeds overwintering on the soil surface were not greatly affected with more than 96% remaining viable seed. With high soil moisture, emergence patterns were influenced by fluctuations in temperatures in late May when emergence began, to June. In July and early August when emergence ceased, soil moisture became the limiting factor. Total emergence was greatest when all competition was removed. Both intraspecific and corn competition reduced emergence in July and early August. Cultivation acted to remove competition resulting in greater total emergence than treatments with competition

Multivariate Fitting and the Error Matrix in Global Analysis of Data

When a large body of data from diverse experiments is analyzed using a theoretical model with many parameters, the standard error matrix method and the general tools for evaluating errors may become inadequate. We present an iterative method that significantly improves the reliability of the error matrix calculation. To obtain even better estimates of the uncertainties on predictions of physical observables, we also present a Lagrange multiplier method that explores the entire parameter space and avoids the linear approximations assumed in conventional error propagation calculations. These methods are illustrated by an example from the global analysis of parton distribution functions.Comment: 13 pages, 5 figures, Latex; minor clarifications, fortran program made available; Normalization of Hessian matrix changed to HEP standar