117 research outputs found
Bidentate N,O-prolinate ruthenium benzylidene catalyst highly active in RCM of disubstituted dienes
The synthesis of a bidentate N,O-prolinate ruthenium benzylidene from commercially available starting materials and its activity in ring-closing metathesis of functionalized disubstituted dienes at 30 °C is disclosed
A Community of Voices: Using Allegory as an Interpretive Device in Action Research on Organizational Change
Organizational change involves patterns of engagement across organizational lines and thus carries important cultural implications for participants and groups within communities of organizations. This article proposes using allegory as an interpretive device in the study of organizational change. Allegory allows organizational research to appreciate the way “characters” introduce distinct qualities into the change experience. Based on an action research program with public organizations in the state of Delaware, the article reveals the promise of allegory both for explicating theory and informing reflexive practice
The Effects of Triclosan Derivatives against the Growth of Staphylococcus Aureus
Triclosan is an antimicrobial commonly used in many different antiseptics and everyday products. Unfortunately, many bacteria are now resistant to triclosan due to innate resistance, mutations in the fabI gene, and/or overexpression of certain other genes (soxS, marA, and an efflux pump encoded by acrAB). Therefore, it is essential that drugs be developed to destroy bacteria now resistant to triclosan. In this experiment, four different derivatives of triclosan were tested for antibacterial capabilities under the supervision of Dr. Hubbard at Liberty University. The derivatives were synthesized by Professor McGibbon (professor of organic chemistry at LU). Solutions of 4.0 ug/mL of each derivative were made and then tested against S. aureus for inhibition capabilities. Some of the derivatives seemed to have some inhibition capabilities, but none of them were as inhibitive as triclosan itself. Of special note, some of the results seem to indicate that the added benzene ring may inactivate triclosan’s antibacterial capabilities while the added chlorines provide at least some inhibition to S. aureus. Ultimately, the derivatives of triclosan did not have high inhibition rates at 4.0 ug/mL, but more experiments need to be performed in order to determine their effects at higher concentrations and on different species of bacteria. Hopefully, the data gathered and inferred from this experiment, including several valuable dissolving ratios and laboratory techniques which were discovered, will be implemented into future research on triclosan derivatives that will lead to the discovery of compounds even more inhibitive against bacteria growth than triclosan
Instrument Development of the UNC Dry Eye Management Scale
Dry Eye Disease (DED) is a chronic disease that diminishes the quality of life (QOL) of millions of Americans. Clinical tests of DED poorly correlate with patient-reported symptoms, and current dry eye questionnaires that include QOL measures require considerable time and effort to complete. Therefore, as part of a research team in the University of North Carolina (UNC) Ophthalmology Department, I helped develop a single-item, patient-reported dry eye scale that conveys both the patient’s dry eye symptoms and the effects of these symptoms on the patient’s quality of life. Our initial questionnaire development consisted of two phases: conceptualization and questionnaire development and cognitive interviewing and questionnaire modification. During phase one, we performed an extensive literature review and consulted multiple patients and experts to create the conceptual framework for our dry eye questionnaire. During phase 2, we administered this preliminary questionnaire to multiple dry eye patients; then, using cognitive interviewing techniques, we asked these patients several questions about the questionnaire. In total, 18 patients were interviewed, and their input led to further modifications of our dry eye scale and ultimately led to the final product: the UNC Dry Eye Management Scale (UNC DEMS). Validity and reliability testing of this dry eye scale are ongoing, but early statistical analyses indicate that the UNC DEMS is a valid patient-reported measure of both symptoms and QOL in DED. Our hope is that this tool will assist both clinicians and patients in the monitoring and management of DED in the time-constricted clinical setting.Master of Public Healt
Ring-opening metathesis polymerization (ROMP) of norbornene by a Group VIII carbene complex in protic media
During the past two decades, intense research efforts have enabled an in-depth understanding of the olefin metathesis reaction as catalyzed by early transition metal complexes. In contrast, the nature of the intermediates and the reaction mechanism for group VIII transition metal metathesis catalysts remain elusive. Such knowledge is important in view of the promise group VIII metals show in polymerizing a wide variety of functionalized cyclic olefins in protic solvents. Highly active late transition metal catalysts should also open the way to the metathesis of functionalized acyclic olefins. Previous studies in our group have focused on the chemistry of highly active, functional-group-tolerant catalysts prepared from aquoruthenium(II) olefin complexes. In these systems, characterization of the catalytic intermediates is difficult due to their very low concentrations and high activity in the reaction mixtures. Although it is reasonable to assume that the active species are ruthenacyclobutanes and ruthenium carbenes (ruthenaolefins), the oxidation state and ligation of these intermediates are not known. Furthermore, the discrete ruthenium carbene complexes that have been isolated to date do not exhibit both metathesis activity and stability to protic/aqueous solvents. We report here the reaction of an Ru(II) complex with a strained olefin to produce a carbene species that polymerizes norbornene in organic media both in the absence and presence of protic/aqueous solvents. In both solvent systems, a stable propagating carbene complex can be observed throughout the course of the polymerization, as has been previously found with titanium, tantalum, tungsten, molybdenum, and ruthenium complexes
Facile tungsten alkylidene synthesis: alkylidene transfer from a phosphorane to a tungsten imido complex
A number of transition-metal complexes catalyze the ring-opening metathesis polymerization (ROMP) of a variety of cyclic olefins. Notable among these catalysts are the titanacyclobutane derivatives and certain alkylidene complexes of tungsten: molybdenum, tantalum, and rhenium. The highly reactive tungsten alkylidene complexes developed by Schrock, Osborn, and Basset are particularly useful for the synthesis of unsaturated polymers such as novel conducting polymers and soluble precursors and derivatives of polyacetylene. Recent applications of these catalytic systems involve the polymerization of acyclic alkynes and dienes In addition, the use of tungsten alkylidene complexes as Wittig-type reagents in organic synthesis holds considerable promise
Second-order nonlinearities and crystal structure of 2-methoxy-4'-nitro-(E)-stilbene
Second-order nonlinear optical (NLO) properties of crystalline materials depend both on the magnitude of the molecular hyperpolarizability (β) and on the orientation of the chromophores in the crystal lattice. If the molecular hyperpolarizability is to result in a nonzero macroscopic nonlinearity, the molecule must crystallize in a noncentrosymmetric space group. The design of new second-order NLO materials requires one both to address the structure-property relationships that govern β and to develop methodologies that favor noncentrosymmetric crystallization. Methods used to encourage noncentrosymmetric crystallization include the use of chiral molecules, the incorporation of functional groups that encourage asymmetric intermolecular hydrogen bonding, the synthesis of molecules with very small ground-state dipole moments but larger excited-state dipole moments, and the variation of counterion with ionic chromophore
Synthesis, Structure, and Reactivity of a Rhenium Oxo-Vinylalkylidene Complex
The reaction of 3 equiv of KOC(CF_3)_2Me with ReOCl_3(PPh_3)_2 in dichloromethane, followed by recrystallization from hexanes/THF, gives ReO[OC(CF_3)_2Me]_3(THF)_2( 1) in 35 7% yield. An
X-ray diffraction study of 1 (monoclinic, P2_1/n, a = 10.010(3) Å, b = 29.247(6) Å, c = 10.800(3) Å, β = 117.09(1)', Z = 4) reveals a facial arrangement of the three alkoxide ligands around the metal center in a distorted octahedron. The ligand environment in 1 is quite crowded, as evidenced by an elongated Re-O bond between rhenium and one of the THF ligands. The reaction of 3,3-diphenylcyclopropene with 1 in dichloromethane gives initially a mixture of two isomeric rhenium oxo-vinylalkylidene complexes, of which the isomer syn,mer-ReO[C(H)-CH=CPh_2] [OC(CF3)2Me]3(THF) (2b) was isolated in 87% yield. An X-ray diffraction study of 2b (triclinic, P1^(bar), a = 10.459(3) Å, b = 10.913(3) Å, c = 21.308(6) Å, α = 91.16(3)°,β = 102.05-(2)°, γ = 117.98(2)°, 2 = 2) supports a pseudooctahedral structure with mutually trans vinylalkylidene and THF ligands. Complex 2b does not react readily with internal or terminal olefins; however, the addition of GaBr_3 (1 equiv) to 2b yields moderately active catalyst(s) that metathesize cis-2-pentene at ~6.7 turnovers min^(-1). No propagating alkylidene species are observed during the metathesis reaction
Autoimmunity in the Pathogenesis and Treatment of Keratoconjunctivitis Sicca
Dry eye is a chronic corneal disease that impacts the quality of life of many older adults. keratoconjunctivitis sicca (KCS), a form of aqueous-deficient dry eye, is frequently associated with Sjögren’s syndrome and mechanisms of autoimmunity. For KCS and other forms of dry eye, current treatments are limited, with many medications providing only symptomatic relief rather than targeting the pathophysiology of disease. Here, we review proposed mechanisms in the pathogenesis of autoimmune-based KCS: genetic susceptibility and disruptions in antigen recognition, immune response, and immune regulation. By understanding the mechanisms of immune dysfunction through basic science and translational research, potential drug targets can be identified. Finally, we discuss current dry eye therapies as well as promising new treatment options and drug therapy targets
Return of Positive Test Results to Participants in Sexually Transmitted Infection Prevalence Studies: Research Ethics and Responsibilities
Background: In prevalence studies of sexually transmitted infections (STIs), investigators often provide syndromic management for symptomatic participants, but may not provide specific treatment for asymptomatic individuals with positive laboratory test results due to the delays between sample collection and availability of results as well as logistical constraints in recontacting study participants. Methods: To characterize the extent of this issue, 80 prevalence studies from the World Health Organization’s Report on global sexually transmitted infection surveillance, 2018, were reviewed. Studies were classified as to whether clinically relevant positive results were returned or if this was not specified. Results: More than half (56%) of the cited studies did not specify if participants were notified of clinically relevant positive STI test results. The percentages were similar for low- and middle-income country populations (57%) and high-income country populations (53%). Conclusions: The absence of documentation of the provision of test results raises the possibility that in some instances, results may not have been communicated, with potential negative effects for participants, their sexual partners, and newborns. From an ethical perspective, clinically relevant results should be returned to study participants and treating clinicians in a timely fashion to ensure appropriate management of identified infections. Study authors should document if they returned test results to study participants and report on numbers lost to follow-up
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