Thermochemical tests on resins: Char resistance of selected phenolic cured epoxides

Curing epoxy resins with novalac phenolic resins is a feasible approach for increasing intact char of the resin system. Char yields above 40% at 700 C were achieved with epoxy novalac (DEN 438)/novalac phenolic (BRWE 5833) resin systems with or without catalyst such as ethyl tri-phenyl phosphonium iodide. These char yields are comparable to commercially used epoxy resin systems like MY-720/DDS/BF3. Stable prepregs are easily made from a solvent solution of the epoxy/phenolic system and this provides a feasible process for fabrication of same into commercial laminates

Formulation and Characterization of Epoxy Resin Copolymer for Graphite Composites

Maximum char yield was obtained with a copolymer containing 25% mol fraction DGEBE and 75% mol fraction DGEBA (Epon 828). To achieve the high values (above 40%), a large quantity of catalyst (trimethoxyboroxine) was necessary. Although a graphite laminate 1/8" thick was successfully fabricated, the limited life of the catalyzed epoxy copolymer system precludes commercial application. Char yields of 45% can be achieved with phenolic cured epoxy systems as indicated by data generated under NAS2-10207 contract. A graphite laminate using this type of resin system was fabricated for comparison purposes. The resultant laminate was easier to process and because the graphite prepreg is more stable, the fabrication process could readily be adapted to commercial applications

An Examination and Critique of the Compatibility and Coherence of Brian Leiter’s Naturalized Jurisprudence with the American Legal Framework

In this thesis I argue Brian Leiter’s vision for a naturalized jurisprudence stands in problematic tension with critical facets of objective morality presupposed by the American legal system. Leiter makes the case for the naturalization of jurisprudence through adherence to his version of a naturalistic epistemology. Though Leiter explicitly rejects moral realism—and embraces elements of legal positivism—he acquiesces to the notion that judges sometimes utilize non-legal, “moral reasons,” when deciding cases. Leiter suggests that any moral “knowledge” that may influence the process of adjudication should be delivered by the hard sciences. I suggest Leiter’s epistemological naturalism is incapable of providing the normative, prescriptive, and proscriptive moral propositions that are integral to the American legal system. Moreover, Leiter’s denial of objective moral values is inconsistent with a legal framework predicated on securing the life and rights of objectively valuable and equal human beings. Through myriad appeals to God, and contemporary locutions thereof, the American founders constructed an enduring legal framework that presupposed the existence of a transcendent and objective moral law. This moral law is often referred to as the law of nature. The law of nature is commensurate with certain objective moral facts and values—especially those germane to the innate moral value of human life. Moreover, the intrinsic worth of human beings helps explain the focus the founders placed on securing our preexistent rights and duties. These same preexistent values, rights, and duties are pertinent to safeguarding the conditions by which we may flourish. I suggest Christian theism is a reasonable and plausible worldview for providing the ontological grounding and epistemic accessibility required for a robust natural law conception as held by the founders. Moreover, Christian theism helps explain the unique value of human life that is a vitally integral element of contemporary law. I conclude that Leiter’s effort to naturalize jurisprudence stands in tension with a jurisprudence as envisioned by the founders. Moreover, I suggest that a natural law theory of objective moral values—viewed through the lens of Christian theism—better coheres with the American founding and enduring legal system than Leiter’s naturalized jurisprudence

The Music Box : Imitation

https://digitalcommons.library.umaine.edu/mmb-ps/1833/thumbnail.jp

Coupling DNA-binding and ATP hydrolysis in Escherichia coli RecQ: role of a highly conserved aromatic-rich sequence

RecQ enzymes are broadly conserved Superfamily-2 (SF-2) DNA helicases that play critical roles in DNA metabolism. RecQ proteins use the energy of ATP hydrolysis to drive DNA unwinding; however, the mechanisms by which RecQ links ATPase activity to DNA-binding/unwinding are unknown. In many Superfamily-1 (SF-1) DNA helicases, helicase sequence motif III links these activities by binding both single-stranded (ss) DNA and ATP. However, the ssDNA-binding aromatic-rich element in motif III present in these enzymes is missing from SF-2 helicases, raising the question of how these enzymes link ATP hydrolysis to DNA-binding/unwinding. We show that Escherichia coli RecQ contains a conserved aromatic-rich loop in its helicase domain between motifs II and III. Although placement of the RecQ aromatic-rich loop is topologically distinct relative to the SF-1 enzymes, both loops map to similar tertiary structural positions. We examined the functions of the E.coli RecQ aromatic-rich loop using RecQ variants with single amino acid substitutions within the segment. Our results indicate that the aromatic-rich loop in RecQ is critical for coupling ATPase and DNA-binding/unwinding activities. Our studies also suggest that RecQ's aromatic-rich loop might couple ATP hydrolysis to DNA-binding in a mechanistically distinct manner from SF-1 helicases

On Estimating the High-Energy Cutoff in the X-ray Spectra of Black Holes via Reflection Spectroscopy

The fundamental parameters describing the coronal spectrum of an accreting black hole are the slope $\Gamma$ of the power-law continuum and the energy $E_{cut}$ at which it rolls over. Remarkably, this parameter can be accurately measured for values as high as 1 MeV by modeling the spectrum of X-rays reflected from a black hole accretion disk at energies below 100 keV. This is possible because the details in the reflection spectrum, rich in fluorescent lines and other atomic features, are very sensitive to the spectral shape of the hardest coronal radiation illuminating the disk. We show that fitting simultaneous NuSTAR (3-79 keV) and low-energy (e.g., Suzaku) data with the most recent version of our reflection model RELXILL, one can obtain reasonable constraints on $E_{cut}$ at energies from tens of keV up to 1 MeV, for a source as faint as 1 mCrab in a 100 ks observation.Comment: Accepted for publication in ApJL, 6 pages, 5 figure

A Suzaku, NuSTAR, and XMM-Newton view on variable absorption and relativistic reflection in NGC 4151

We disentangle X-ray disk reflection from complex line-of-sight absorption in the nearby Seyfert NGC 4151, using a suite of Suzaku, NuSTAR, and XMM-Newton observations. Extending upon earlier published work, we pursue a physically motivated model using the latest angle-resolved version of the lamp-post geometry reflection model relxillCp_lp together with a Comptonization continuum. We use the long-look simultaneous Suzaku/NuSTAR observation to develop a baseline model wherein we model reflected emission as a combination of lamp-post components at the heights of 1.2 and 15.0 gravitational radii. We argue for a vertically extended corona as opposed to two compact and distinct primary sources. We find two neutral absorbers (one full-covering and one partial-covering), an ionized absorber ($\log \xi = 2.8$), and a highly-ionized ultra-fast outflow, which have all been reported previously. All analyzed spectra are well described by this baseline model. The bulk of the spectral variability between 1 keV and 6 keV can be accounted for by changes in the column density of both neutral absorbers, which appear to be degenerate and inversely correlated with the variable hard continuum component flux. We track variability in absorption on both short (2 d) and long ($\sim$1 yr) timescales; the observed evolution is either consistent with changes in the absorber structure (clumpy absorber at distances ranging from the broad line region (BLR) to the inner torus or a dusty radiatively driven wind) or a geometrically stable neutral absorber that becomes increasingly ionized at a rising flux level. The soft X-rays below 1 keV are dominated by photoionized emission from extended gas that may act as a warm mirror for the nuclear radiation.Comment: 21 pages, 19 figures, 8 tables, accepted for publication by A&

Glendale Waltz

https://digitalcommons.library.umaine.edu/mmb-ps/2080/thumbnail.jp

Toward the Development of a Quick, Reliable Assessment Tool for Reflective Journals

Reflective practice, including reflective writing, can facilitate enriched learning, especially when implemented as part of a service-learning (SL) experience. Reflection is a central component of service-learning (SL) experiences. Students’ reflective abilities are often measured through reflective journaling; however, assessment of students’ reflective journals is not always efficient and straightforward. The goal of the present study was to establish a simple, reliable, and relatively quick tool for use by busy college instructors seeking to encourage students’ deep learning through reflective writing. A total of 258 reflective journals from 43 graduate students in speech-language pathology were evaluated by three raters using a three-tier assessment framework (nonreflection, reflection, and critical reflection) after Mezirow (1990) and Plack et al. (2005). Although previous studies found moderate to high interrater agreement and reliability, the current study did not support this finding. Strengths and weaknesses of the assessment framework and qualitative observations of the assessment process are discussed