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Shearer, Gretchen L.,Kim, Keehyuk,Lee, Kang Man,Wang, Kathy C.,Plapp, Bryce V. 梨花女子大學校 藥學硏究所 1994 藥學硏究論文集 Vol.- No.4
Liver alcohol dehydragenase catalyzes the reaction of NAD^+ and benzyl alcohol to form NADH and benzaldehyde by a predominantly ordered reaction. However, enzyme-alcohol binary and abortive ternary complexes form at high concentrations of benzyl alcohol, and benzaldehyde is slowly oxidized to benzoic acid. Steady-state and transient kinetic studies, equilibrium spectrophotometric measurements, product analysis, and kinetic simulations provide estimates of rate constants for a complete mechanism with the following reactions: (1) E??E-NAD^+?? E-NAD^+-RCH_2OH ?? E-NADH-RCHO??E-NADH??E; (2) E-NADH??E-NADH-RCH_2OH??E-RCH_2OH??E; (3) E-NAD^+ ?? E-NAD^+-RCHO → E-NADH-RCOOH??E-NADH. The internal equilibrium constant for hydrogen transfer determined at 30℃ and pH7 is about 5:1 in favor of E-NAD^+-RCH_2OH and has a complex pH dependence. Benzyl alcohol binds weakly to free enzyme (K_d=7mM) and significantly decreases the rates of binding of NAD^+ and NADH. The reaction of NAD^+ and benzyl alcohol is therefore kinetically ordered, not random. High concentrations of benzyl alcohol (>1 mM) inhibit turnover by formation of the abortive E-NADH-RCH_2-OH complex, which dissociates at 0.3s^-1 as compared to 6.3s^-1 for E-NADH. The oxidation of benzaldehyde by E- NAD^+(K_m=15mM, V/E = 0.4 s^-1 ) is inefficient relative to the oxidation of benzyl alcohol (K_m=28 ㎛, V/E = 3.1 s^-1) and leads to a dismutation (2RCHO → RCH_2OH + RCOOH) as E-NADH reduces benzaldehyde. The results provide a description of final product distributions for the alternative reactions catalyzed by the multifunctional enzyme.
Rick L. Shearer 한국방송통신대학교 미래원격교육연구원 2017 평생학습사회 Vol.13 No.1
This paper takes an exploratory look at the constructs of competency-based education (CBE) and adaptive learning and their possible impacts on distance education and the adult learner. As re-emerging constructs within the higher education landscape it is important to track the history of these concept, how they have been implemented in the past, and how they may be implemented in the future to benefit adult learners studying at a distance. This paper also examines how the constructs fit within the theory of transactional distance and the community of inquiry model, and how higher education, specifically in the United States, may need to change in order to allow adaptive learning and competency-based approaches to be integrated into institutions. Although this paper is a snap shot of the status of these constructs, it will be important to continue to track these concepts to understand which systems and models work and which may not have promise for our learners.
3D SIMULATIONS OF RADIO GALAXY EVOLUTION IN CLUSTER MEDIA
O'NEILL SEAN M.,SHEARER PAUL,TREGILLIS IAN L.,JONES THOMAS W.,RYU DONGSU The Korean Astronomical Society 2004 Journal of The Korean Astronomical Society Vol.37 No.5
We present a set of high-resolution 3D MHD simulations exploring the evolution of light, supersonic jets in cluster environments. We model sets of high- and low-Mach jets entering both uniform surroundings and King-type atmospheres and propagating distances more than 100 times the initial jet radius. Through complimentary analyses of synthetic observations and energy flow, we explore the detailed interactions between these jets and their environments. We find that jet cocoon morphology is strongly influenced by the structure of the ambient medium. Jets moving into uniform atmospheres have more pronounced backflow than their non-uniform counterparts, and this difference is clearly reflected by morphological differences in the synthetic observations. Additionally, synthetic observations illustrate differences in the appearances of terminal hotspots and the x-ray and radio correlations between the high- and low-Mach runs. Exploration of energy flow in these systems illustrates the general conversion of kinetic to thermal and magnetic energy in all of our simulations. Specifically, we examine conversion of energy type and the spatial transport of energy to the ambient medium. Determination of the evolution of the energy distribution in these objects will enhance our understanding of the role of AGN feedback in cluster environments.
Direct Chemical Vapor Deposition Synthesis of Phase-Pure Iron Pyrite (FeS<sub>2</sub>) Thin Films
Samad, Leith,Cabá,n-Acevedo, Miguel,Shearer, Melinda J.,Park, Kwangsuk,Hamers, Robert J.,Jin, Song American Chemical Society 2015 Chemistry of materials Vol.27 No.8
<P>Resurgent interest in iron pyrite (FeS<SUB>2</SUB>) as an earth-abundant, nontoxic semiconductor for solar applications has resulted in many attempts to grow phase-pure thin films via chemical vapor deposition (CVD). However, all thin films grown via CVD or sulfidation to date have contained marcasite phase or other iron sulfide impurities. Here, we report the use of metallic cobalt pyrite (cattierite, CoS<SUB>2</SUB>) thin films as an ideal substrate leading to the first direct growth of phase-pure iron pyrite thin films via atmospheric pressure CVD. This synthesis was achieved by reacting FeCl<SUB>3</SUB> and ditert butyl disulfide (TBDS) at 400–450 °C. The products were confirmed as phase-pure iron pyrite using X-ray diffraction (XRD), Raman spectroscopy, and energy dispersive X-ray spectroscopy (EDS). In addition to phase-purity, the synthesis produced crystal domains >1 μm and a conformal coating 3–5 μm thick, which are attributed to the <2% lattice mismatch of the isostructural cattierite substrate. The surface was characterized by ultraviolet and X-ray photoelectron spectroscopy (UPS & XPS) and the electrical properties by electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis. The direct growth of a phase-pure iron pyrite film on a conductive substrate provides the most convenient configuration so far for potential solar cells.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-8/acs.chemmater.5b00664/production/images/medium/cm-2015-00664c_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5b00664'>ACS Electronic Supporting Info</A></P>
A Review on the Effect of Soil Compaction and its Management for Sustainable Crop Production
Shaheb Md Rayhan,Venkatesh Ramarao,Shearer Scott A. 한국농업기계학회 2021 바이오시스템공학 Vol.46 No.4
Purpose Sustainable crop production could contribute to feed and fuel for the ever-increasing global population. The use of heavy agricultural machinery has improved the efficiency of farming operations and increased global food production since the 1950s. But their negative impact on soil includes changing soil structure resulting in deteriorating soil productivity and environmental quality is being noticed for several decades. The purpose of this review is to summarize and help to better understand the effect of heavy machinery, tire inflation pressure, and field traffic on soil properties and crop development, yield, and economics of different farming systems published in the last 20 years. Methods Search engines such as Google Scholar, Scopus, Science Direct, Springer Link, Wiley Online, Taylor & Francis Online, Academia, and Research Gate platforms were used to collect and review the articles. This review includes indexed journals, conference and symposium proceedings, reports, academic presentations, and thesis/dissertations. Results Soil compaction increases bulk density and soil strength and reduces soil porosity and soil hydraulic properties. Stunted plant root growth due to compaction of soil affects crop growth and development, and yield. Soil compaction resulting from heavy machinery traffic caused a significant crop yield reduction of as much as 50% or even more, depending upon the magnitude and the severity of compaction of the soil. Conclusions High gross weight vehicles/machinery traffic damages soil structure and soil environment that are critical for sustainable crop production. The use of heavy machinery such as subsoiling for removing soil compaction results in more fuel use, increased use of energy, cost, and sometimes risks of re-compaction, further deteriorating soil conditions and causing additional adverse environmental consequences. The economics of different farming systems affected by soil compaction, potential soil compaction management strategies, and future research needs have also been discussed.
Tcho, Woon-Young,Wang, Bin,Lee, Yong-Min,Cho, Kyung-Bin,Shearer, Jason,Nam, Wonwoo The Royal Society of Chemistry 2016 Dalton Transactions Vol.45 No.37
<P>A mononuclear nonheme cobalt(III)-hydroperoxide complex bearing a tetramethylated cyclam ligand, [(12-TMC)Co-III(OOH)](2+), was synthesized and characterized spectroscopically and computationally; the cobalt(III)-hydroperoxide complex exhibited an amphoteric reactivity in electrophilic and nucleophilic oxidative reactions.</P>
KIM, KYUNG H.,PARK, MOON K.,PEETERS, CARLA C.,POOLMAN, J.T.,SHEARER, MICHAEL H.,KENNEDY, RONALD C.,NAHM, MOON H. 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.17 No.-
Nonhuman primates are often used as a model for studying vaccines for humans. However, it is not always clear how closely the antibody responses in these species mimic human responses. Recent studies have characterized the human antibody response to Haemophilus influenzae type b (Hib) in great detail. In this study, we have compared the antibody response to Hib of humans with those of other primates. Studies of isoelectric points and V_K subgroup usage show that, like humans, nonhuman primates produce oligoclonal antibodies. Also, monkey antibodies to the Hib polysaccharide are as protective as human antibodies in an in vivo model of Hib infection. Thus, we conclude that nonhuman primates produce antibodies to Hib polysaccharide that are structurally and functionally similar to human antibodies and are a good model for testing human vaccines.