195,999 research outputs found
Induced chirality-at-metal and diastereoselectivity at Delta/Delta-configured distorted square-planar copper complexes by enantiopure Schiff base ligands: combined circular dichroism, DFT and X-ray structural studies
No full textBidentate enantiopure Schiff base ligands, (R or S)-N-1-(Ar) ethyl-2-oxo-1-naphthaldiminato-kappa N-2,O, diastereoselectively yield Delta/Delta-chiral four-coordinated, non-planar Cu((NO)-O-boolean AND)(2) complexes [Ar = C6H5 R/S-L1, m-C6H4OMe R-L2, p-C6H4OMe R/S-L3, and p-C6H4Br R/S-L4]. Two N,O-chelate ligands coordinate to the copper(II) atom in distorted square-planar mode, and induce metal-centered Delta/Delta-chirality at the copper atom in the C-2-symmetric complexes. In the solid state, the R-L1 (or R-L4) ligand chirality diastereoselectively induces a Delta-Cu configuration in Delta-Cu-R-L1 (or Delta-Cu-R-L4), the S-L1 ligand a Delta-Cu configuration in Delta-Cu-S-L1, forming enantiopure crystals upon crystallization. Conversely, the R-L2 ligand combines both Delta/Delta-Cu-R-L2 as a diastereomeric pair in the crystals. In solution, electronic circular dichroism (CD) spectra show full or partial diastereoselectivity towards Delta-Cu for R ligands and towards Delta-Cu for S ligands. The electronic CD spectra measured on all complexes obtained from R ligands (or S ligands), e.g. Cu-R-L1, Cu-R-L2, Cu-R-L3, and Cu-R-L4 (or Cu-S-L1, Cu-S-L3, and Cu-S-L4), show consistent spectral features. TDDFT calculations of the electronic CD spectra for the diastereomers Delta-Cu-R-L1 and.-Cu-R-L1 suggest that the CD spectra are largely dominated by the configuration at the metal center (Delta vs. Delta). The experimental CD spectrum of Cu-R-L1 agrees well with the one calculated for the Delta-Cu-R-L1 configuration. Cyclic voltammetry of Cu-R-L1 reveals a quasi-reversible redox wave corresponding to one-electron transfer for the [(CuL2)-L-II](0)/[(CuL2)-L-I](-1) couple in acetonitrile. DSC analyses for the complexes show an exothermic peak between 377 and 478 K (Delta H = -12 to -43 kJ mol(-1)), corresponding to a phase transformation from distorted square-planar/tetrahedral to regular tetrahedral geometry on heating
Synthesis and Characterization of Bis[(RorS)-N-1-(X-C6H4)ethyl-2-oxo-1-naphthaldiminato-κ2N,O]-Λ/Δ-cobalt(II) (X = H,p-CH3O,p-Br) with Symmetry- And Distance-Dependent Vibrational Circular Dichroism Enhancement and Sign Inversion
No full textThe enantiopure Schiff bases (RorS)-N-1-(X-C6H4)ethyl-2-hydroxy-1-naphthaldimine {X = H [(RorS)-HL1],p-CH3O [(RorS)-HL2], andp-Br [(R- orS)-HL3]} react with cobalt(II) acetate to give bis[(RorS)-N-1-(X-C6H4)ethyl-2-oxo-1-naphthaldiminato-κ2N,O]-Λ/Δ-cobalt(II) {X = H [Λ/Δ-Co-(RorS)-L1],p-CH3O [Λ/Δ-Co-(RorS)-L2], andp-Br [Λ/Δ-Co-(RorS)-L3]} ( 1 - 3 ), respectively. Induced Λ and Δ chirality originates at the metal center of theC2-symmetric molecule in pseudotetrahedral geometry. Differential scanning calorimetry analyses explored the thermal stability of the complexes, which undergo reversible phase transformation from crystalline solid to isotropic liquid phase for 1 and 3 but irreversible phase transformation for 2 . Like other cobalt(II) complexes, compounds 1 - 3 exhibit a continuous ensemble of absorption and circular dichroism bands, which span from the UV to IR region and can be collected into a superspectrum. Infrared vibrational circular dichroism (IR-VCD) spectra witness the coupling between Co2+-centered low-lying electronic states and ligand-centered vibrations. The coupling produces enhanced and almost monosignate VCD spectra, with both effects being mode-dependent in terms of theAorBsymmetry (in theC2point group) and distance from the Co2+core
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
Simulation of thermal plant optimization and hydraulic aspects of thermal distribution loops for large campuses
No full textFollowing an introduction, the author describes Texas A&M University and its utilities system. After that, the author presents how to construct simulation models for chilled water and heating hot water distribution systems. The simulation model was used in a $2.3 million Ross Street chilled water pipe replacement project at Texas A&M University. A second project conducted at the University of Texas at San Antonio was used as an example to demonstrate how to identify and design an optimal distribution system by using a simulation model. The author found that the minor losses of these closed loop thermal distribution systems are significantly higher than potable water distribution systems. In the second part of the report, the author presents the latest development of software called the Plant Optimization Program, which can simulate cogeneration plant operation, estimate its operation cost and provide optimized operation suggestions. The author also developed detailed simulation models for a gas turbine and heat recovery steam generator and identified significant potential savings. Finally, the author also used a steam turbine as an example to present a multi-regression method on constructing simulation models by using basic statistics and optimization algorithms. This report presents a survey of the author??s working experience at the Energy Systems Laboratory (ESL) at Texas A&M University during the period of January 2002 through March 2004. The purpose of the above work was to allow the author to become familiar with the practice of engineering. The result is that the author knows how to complete a project from start to finish and understands how both technical and nontechnical aspects of a project need to be considered in order to ensure a quality deliverable and bring a project to successful completion. This report concludes that the objectives of the internship were successfully accomplished and that the requirements for the degree of Degree of Engineering have been satisfied
Synthesis, X-ray, and Spectroscopic Study of Dissymmetric Tetrahedral Zinc(II) Complexes from Chiral Schiff Base Naphthaldiminate Ligands with Apparent Exception to the ECD Exciton Chirality
No full textBidentate enantiopure Schiff base ligands, (R or S)-N-1-(Ar)ethyl-2-oxo-1-naphthaldiminate (R- or S-N^O), diastereoselectively provide λ- or δ-chiral-at-metal four-coordinated Zn(R- or S-N^O)2 Ar = C6H5; Zn-1R or Zn-1S and p-C6H4OMe; Zn-2R or Zn-2S. Two R- or S-N^O-chelate ligands coordinate to the zinc(II) in a tetrahedral mode and induce λ- or δ-configuration at the zinc metal center. In the solid state, the R- or S-ligand diastereoselectively gives λ- or δ-Zn configuration, respectively, and forms enantiopure crystals. Single crystal structure determinations show two symmetry-independent molecules (A and B) in each asymmetric unit to give Z′ = 2 structures. Electronic circular dichroism (ECD) spectra show the expected mirror image relationship resulting from diastereomeric excess toward the λ-Zn for R-ligands and δ-Zn for S-ligands in solution. ECD spectra are well reproduced by TDDFT calculations, while the application of the exciton chirality method, in the common point-dipole approximation, predicts the wrong sign for the long-wavelength couplet. A dynamic diastereomeric equilibrium (λ vs δ) prevails for both R- and S-ligand-metal complexes in solution, respectively, evidenced by 1H NMR spectroscopy. Variable temperature 1H NMR spectra show a temperature-dependent shift of the diastereomeric equilibrium and confirm δ-Zn configuration (for S-ligand) to be the most stable one and favored at low temperature. DSC analyses provide quantitative diastereomeric excess in the solid state for Zn-2R and Zn-2S, which is comparable to the results of solution studies
Intern experience at CH���M Hill, Inc.: an internship report
No full textIncludes author's vita"Submitted to the College of Engineering of Texas A&M University in partial
fulfillment of the requirement for the degree of Doctor of Engineering."Includes bibliographical referencesA review of the author's internship experience with CH���M HILL, Inc.
during the period September 1975 through May 1976 is presented. During this nine month
internship the author worked as an Engineer II in the Industrial Processes discipline of this
large consulting engineering firm... The author's prime responsibility was as one of three
lead design engineers on the design of a large wastewater treatment facility for a pulp mill
in Hoquiam, Washington owned by ITT Rayonier Inc. The work generally consisted of the design
of individual treatment units and associated piping and pumping. The purpose of the project
was to provide wastewater treatment capabilities that would satisfy the effluent limitations
(standards) imposed upon the mill by the State of Washington Department of Ecology and the
U.S. Environmental Protection Agency. The author's assignment also entailed necessary
interaction with the project manager and other CH���M HILL design engineers and support staff
members, the client's representatives, and representatives of two other consulting engineering
firms working on the project. Thus, the internship position at CH���M HILL provided considerable
experience coordinating the author's work with the work of other engineers, guiding the design
and administrative efforts of a support staff, and interacting regularly with the client and
other consulting firms. This broad exposure to a variety of engineering and organizational
problems provided a valuable educational experience
Transition to turbulence in a qblique shock-wave/boundary-layer interaction at M=15
No full textDirect numerical simulations are carried out for different forcing techniques to trigger transition during the interaction between an oblique shock-wave and a laminar boundary-layer at M = 1.5. Three forcing methods are used: a) forcing of oblique unstable modes, whose shape and behaviour are determined by the local linear stability theory, b) broadband free-stream acoustic disturbances, and c) a cold plasma flow control device. While the oblique-mode breakdown is dominant for low-amplitude forcing, long streaky structures drive the transition process in a high-amplitude disturbance environment. LES are also performed on the experimental setup by the Institute of Theoretical and Applied Mechanics (ITAM) from Novosibirsk State University with cold plasma actuation. As well as the disturbance type, the effect of Reynolds number and forcing amplitude will be investigated
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