1,288 research outputs found
Imaging deep skeletal muscle structure using a high-sensitivity ultrathin side-viewing optical coherence tomography needle probe
No full textPublished 10 Dec 2013Abstract not availableXiaojie Yang, Dirk Lorenser, Robert A. McLaughlin, Rodney W. Kirk, Matthew Edmond, M. Cather Simpson, Miranda D. Grounds, and David D. Sampso
Frequency mixing in nonlinear interaction of one-way edge-modes of topological photonic crystals
No full textWe investigate topological photonic crystals specially designed such that the frequency band gaps appear around ω0, 2ω0, 3ω0 and, more importantly, each band gap contains exactly one unidirectional edge mode. These one-way edge modes are then utilized to implement key nonlinear frequency mixing processes, such as second- and third-harmonic generation
Photon-pair generation via bound states in the continuum in nonlinear metasurfaces
No full textGeneration of photon pairs in nonlinear materials enables the creation of non-classical entangled photon states.
With ultra-thin metasurfaces, composed of optical nano-resonators, one can enable the ultimate in miniaturising
nonlinear photon sources along with unprecedented configurability. We present a novel design of a nonlinear
metasurface incorporating AlGaAs nanodisks with oligomer-holes, which features symmetry protected bound
states in the continuum. It enables enhanced photon-pair generation at non-degenerate photon frequencies via
spontaneous parametric down-conversion. This opens the potential for quantum-entanglement between photons
at ultra-short time-scales across the visible and infrared regions, leading to new opportunities for quantum
spectroscopy, sensing, and imaging
A New Look At How Rochambeau Quartered His Army in Newport (1780-1781)
No full textFrench officers lived in Newport homes during their sojourn in the town in 1780-81. “A New Look at How Rochambeau Quartered His Army in Newport (1780-1781)” by Alan and Mary M. Simpson is a reprint from the 2003-2004 edition of Newport History (vols. 72-73: 90-121), regarding the French in Newport. It appears here with slight editing and an added appendix and additional images. The article was originally published in Newport History in 1983 (vol. 56, pt. 2 [Spring, 1983]: 30-67]). In their article, the Simpsons tried to puzzle out the process for quartering French officers in Newport and the precise arrangements that were made for them. Using letters, official documents, military records and focusing on two “billeting lists” that have survived, the authors made important discoveries. Their article includes an appendix that gives specific information about French officers’ housing placements in Newport. Historian Alan Simpson (1912-1998) taught history and was a dean at the University of Chicago and was named president of Vassar College where he served from 1964-1977. Alan Simpson published Puritanism in Old New England (1961), and he and his wife, Mary McQueen McEldowney Simpson (1911-2005), the co-author of this article, wrote books and articles on historical topics
A New Look At How Rochambeau Quartered His Army in Newport (1780-1781)
No full textFrench officers lived in Newport homes during their sojourn in the town in 1780-81. “A New Look at How Rochambeau Quartered His Army in Newport (1780-1781)” by Alan and Mary M. Simpson is a reprint from the 2003-2004 edition of Newport History (vols. 72-73: 90-121), regarding the French in Newport. It appears here with slight editing and an added appendix and additional images. The article was originally published in Newport History in 1983 (vol. 56, pt. 2 [Spring, 1983]: 30-67]). In their article, the Simpsons tried to puzzle out the process for quartering French officers in Newport and the precise arrangements that were made for them. Using letters, official documents, military records and focusing on two “billeting lists” that have survived, the authors made important discoveries. Their article includes an appendix that gives specific information about French officers’ housing placements in Newport. Historian Alan Simpson (1912-1998) taught history and was a dean at the University of Chicago and was named president of Vassar College where he served from 1964-1977. Alan Simpson published Puritanism in Old New England (1961), and he and his wife, Mary McQueen McEldowney Simpson (1911-2005), the co-author of this article, wrote books and articles on historical topics
Novel Drop Impact Configurations on Microstructured Surfaces: Non-Newtonian Fluids and Structure Gradients
No full textThis Thesis is concerned with drop impacts of various fluids on micropatterned surfaces. The drop impact on rough surfaces has wide relevance in natural processes and industrial applications. Over the years numerous studies of
liquid drop impact have been conducted on at smooth solid surfaces. In recent times, the introduction of micropatterned surfaces has added new insights with respect to phenomena such as drop spreading and retraction. This Thesis focuses on the effect of micropillar array designs on the droplet impact process
for a range of fluids, including non-Newtonian carbopol solutions. The final part of the Thesis is concerned with drop impacts on gradient surface groove patterns. The experiments with square pillar microarrays involved analyzing high speed videos of drop impacts collected at up to 9300 frames per second (fps) using a dual-view synchronized imaging system. The drop diameters range from 2.5 to 2.7 mm with impact velocities from 1.5 to 2.8 m/s. The fluids used were both Newtonian and non-Newtonian. The range of Weber numbers (We) covered was from 70 to 350 and the Reynold numbers (Re) ranged from 300 to 9500. The ten different surfaces used had pillar pitches of 40 and 60 _m, pillar width of 20 _m for both circular and square pillars, and heights ranging
from 15 to 31 _m. Soft lithography was used to fabricate these micropatterned polydimethylsiloxane (PDMS) surfaces. The influence of micropillar array patterns was analyzed for both Newtonian and non-Newtonian fluids. It was found that the presence of pillars only slightly influences drop spreading irrespective of the fluid used. In the retraction stage, it was found that the drop retraction rate ( _ _) depended on We, the viscosity, the receding contact angle, and the surface pitch for both Newtonian and non-Newtonian fluids. The retraction rate was analyzed with existing scaling models, and most data showed agreement with the scaling / We0:50 . The asymmetry of drop impacts on micropatterned surfaces for different fluids was then studied. For low viscosity fluids, a critical We range was found for the transition from symmetric to asymmetric spreading. It was also found
that the effect of surface pitch and pillar height influences the total number of fingers formed. Directional dependence of finger formation on the pillar microstructure was found to be inconclusive at higher We. However, on-axis finger formation was mostly observed at low We. Finally impacts on grooved surfaces with a gradient of line spacing were studied. For gradient surfaces the drop impact experiments were conducted using water with drop diameters ranging between 1.9 - 2.7 mm. Low impact velocities (0.30 to 0.65 m/s) were used, resulting in low We values (10 - 15). The gradient surfaces were prepared using a laser-etching process with grooves systematically fabricated on aluminum substrates. It was found that the line spacing between the grooves did not influence the drop spreading. During the retraction stage the effect of drop pinning, caused by differences in line spacing, determines the drop outcomes. It is found that the drop roll-o_ distances and bouncing angles are affected by the surface design of the gradients, and that the drop spreading asymmetry is dependent on drop size as well as surface design
Self-cleaning coatings for painted steel roofing
No full textPre-painted steel roofing is extensively used in both residential and commercial constructions. The contamination of such roofs over time due to biological organisms and other environmental pollutants is a significant aesthetic, functional, and environmental problem. Even though semiconductor photocatalytic coatings are a promising approach, the development of an efficient and durable self-cleaning coating system on pre-painted steel has become limited due to some prevailing challenges. Photodegradation of binders and internal paint components, efficient utilization of solar spectrum, replication of natural environmental parameters in simulated/accelerated test methods, and lack of scientific data on pre-painted substrates for long term outdoor applications are some such challenges.
Therefore, this research is mainly undertaken to develop an enhanced photocatalytic self-cleaning coating system with a long-lasting performance for painted steel roofing applications. Some important strategies such as the introduction of an intermediate protective layer, incorporation of two most promising commercial photocatalysts with a photo-chemically stable polysiloxane binder system, and optimisation of TiO2 concentration have been used in developing these novel coating systems. The self-cleaning activity and durability of the developed photocatalytic coating systems were evaluated in the presence of both simulated and natural environmental conditions.
A high degree of self-cleaning activity and extended service life have been obtained with these novel photocatalytic coating systems compared to the benchmark industrial acrylic coating formulations and control pre-painted steel substrate. The introduction of the intermediate polysiloxane protective layer has significantly enhanced both the self-cleaning activity and service life, minimising the diffusion of reactive oxygen species (ROS) into subsequent underneath paint layers. Both photocatalytic self-cleaning activity and the rate of photodegradation have been increased with TiO2 concentration. The DT10 coating system with 10% (w/w) TiO2 loading was found to be the optimum coating formulation to obtain a high degree of self-cleaning activity at a minimum rate of photodegradation in this study. The degrees of surface disfigurement of these coatings that occur under natural environmental exposure conditions have been positively correlated with the results obtained under simulated solar radiation conditions. Also, a linear correlation was observed between real-time N45 and accelerated Altrac weathering exposure conditions, indicating an approximate 2.8 acceleration factor. Also, relatively less photocatalytic activity and higher photodegradation rates were observed in the photocatalytic coatings when applied on a black colored pre-painted steel substrate indicating the influence of underneath paint color on the performance of photocatalytic coatings
Mechanistic Studies on the Decomposition of Photoactive Nitrosyl Hydride (HNO) Precursors
No full textNitroxyl hydride (HNO) is a biologically relevant, highly reactive molecule and is a redox cousin of NO. HNO shows extremely promising pharmacological properties, including treating congestive heart failure. The overarching motivation for this research is to facilitate kinetic and mechanistic studies of HNO with biologically relevant molecules. As HNO rapidly dimerizes in aqueous solution, HNO studies require compounds that release HNO upon demand. However, the release of HNO from thermally decomposing molecules is slow (typically minutes to hours), making kinetic and mechanistic studies challenging.
There is increasing interest in the development of photoactive HNO donor molecules because the use of light to activate HNO release enables a high degree of temporal and spatial control. In an effort to meet this need, a Piloty’s acid derivative comprising an HNO-generating trifluoromethanesulfonamidoxy moiety tethered to the (6-hydroxynaphthalene-2-yl)methyl (6,2-HNM) photocage (4) is evaluated in order to establish if it can rapidly and cleanly generate HNO upon light activation. The photodecomposition of 4 was probed under a range of solvent conditions using a combination of characterization techniques, including ¹H NMR spectroscopy, ¹⁹F NMR spectroscopy, high resolution mass spectrometry (HRMS), steady state fluorescence spectroscopy, and time-resolved transient absorption spectroscopy.
Photodecomposition of donor 4 occurred via two pathways: via concerted C-O and N-S bond cleavages to release ¹HNO, the 6,2-HNM carbocation, and trifluorosulfinate, CF₃SO₂⁻; or via heterolytic N-O bond cleavage to generate the sulfonamide CF₃SO₂NH₂, and 6-hydroxynaphthalene-2-carbaldehyde. The selectivity between the two pathways is highly responsive to solvent. Donor 4 is shown to decompose to selectively release HNO upon excitation in a solvent mixture of 80:20 v/v MeCN to 5 mM phosphate buffer (pH 7.0). HNO characterization was achieved using two trapping molecules, aquacobalamin and glutathione, and from observation of its dimerization product, N₂O. Evidence for concerted heterolytic C-O and N-S bond cleavages versus elimination of CF₃SO₂NHOH was obtained by ¹⁹F NMR spectroscopy under pH conditions where CF₃SO₂NHOH is stable.
¹H NMR and UV-vis spectroscopic titration experiments showed that donor 4 exists in three protonation states (pKa(NH) = 4.39 ± 0.06 and ₚKₐ(NH) = 9.73 ± 0.01, 25.0 ºC, aqueous solution). Importantly, HNO photorelease occurs from donor 4 under conditions where the naphtholic OH is protonated and the nitrogen atom is deprotonated. Despite exhibiting both photoacidity and photobasicity, release of HNO from donor 4 does not require water and hence does not involve excited state proton transfer(s). Indeed, deprotonation of the photoacidic site of donor 4 decreases pathway selectivity for the generation of HNO following photolysis. The time-resolved spectroscopic studies indicate that HNO release may occur on the picosecond timescale following excitation of donor 4 and occurs via the short-lived ¹NO⁻ species (¹HNO/¹NO⁻ ₚKₐ ~23).
Studies were also completed towards determining the rate constant for the reaction between HNO and hydroxycobalamin. A thermally decomposing HNO donor (Piloty’s acid) was used; this HNO donor releases HNO in alkaline conditions. Under alkaline conditions, a pH-dependent mixture of ¹HNO and ³NO⁻ was formed from the decomposition of Piloty’s acid. ³NO⁻ itself is a good reductant, and a reaction of ³NO⁻ and hydroxycobalamin was observed. Furthermore, ³NO⁻ reacts with the product of the reaction between hydroxycobalamin and ¹HNO/³NO⁻ namely nitroxylcobalamin
Mechanistic Studies on the Decomposition of Photoactive Nitrosyl Hydride (HNO) Precursors
No full textNitroxyl hydride (HNO) is a biologically relevant, highly reactive molecule and is a redox cousin of NO. HNO shows extremely promising pharmacological properties, including treating congestive heart failure. The overarching motivation for this research is to facilitate kinetic and mechanistic studies of HNO with biologically relevant molecules. As HNO rapidly dimerizes in aqueous solution, HNO studies require compounds that release HNO upon demand. However, the release of HNO from thermally decomposing molecules is slow (typically minutes to hours), making kinetic and mechanistic studies challenging.
There is increasing interest in the development of photoactive HNO donor molecules because the use of light to activate HNO release enables a high degree of temporal and spatial control. In an effort to meet this need, a Piloty’s acid derivative comprising an HNO-generating trifluoromethanesulfonamidoxy moiety tethered to the (6-hydroxynaphthalene-2-yl)methyl (6,2-HNM) photocage (4) is evaluated in order to establish if it can rapidly and cleanly generate HNO upon light activation. The photodecomposition of 4 was probed under a range of solvent conditions using a combination of characterization techniques, including ¹H NMR spectroscopy, ¹⁹F NMR spectroscopy, high resolution mass spectrometry (HRMS), steady state fluorescence spectroscopy, and time-resolved transient absorption spectroscopy.
Photodecomposition of donor 4 occurred via two pathways: via concerted C-O and N-S bond cleavages to release ¹HNO, the 6,2-HNM carbocation, and trifluorosulfinate, CF₃SO₂⁻; or via heterolytic N-O bond cleavage to generate the sulfonamide CF₃SO₂NH₂, and 6-hydroxynaphthalene-2-carbaldehyde. The selectivity between the two pathways is highly responsive to solvent. Donor 4 is shown to decompose to selectively release HNO upon excitation in a solvent mixture of 80:20 v/v MeCN to 5 mM phosphate buffer (pH 7.0). HNO characterization was achieved using two trapping molecules, aquacobalamin and glutathione, and from observation of its dimerization product, N₂O. Evidence for concerted heterolytic C-O and N-S bond cleavages versus elimination of CF₃SO₂NHOH was obtained by ¹⁹F NMR spectroscopy under pH conditions where CF₃SO₂NHOH is stable.
¹H NMR and UV-vis spectroscopic titration experiments showed that donor 4 exists in three protonation states (pKa(NH) = 4.39 ± 0.06 and ₚKₐ(NH) = 9.73 ± 0.01, 25.0 ºC, aqueous solution). Importantly, HNO photorelease occurs from donor 4 under conditions where the naphtholic OH is protonated and the nitrogen atom is deprotonated. Despite exhibiting both photoacidity and photobasicity, release of HNO from donor 4 does not require water and hence does not involve excited state proton transfer(s). Indeed, deprotonation of the photoacidic site of donor 4 decreases pathway selectivity for the generation of HNO following photolysis. The time-resolved spectroscopic studies indicate that HNO release may occur on the picosecond timescale following excitation of donor 4 and occurs via the short-lived ¹NO⁻ species (¹HNO/¹NO⁻ ₚKₐ ~23).
Studies were also completed towards determining the rate constant for the reaction between HNO and hydroxycobalamin. A thermally decomposing HNO donor (Piloty’s acid) was used; this HNO donor releases HNO in alkaline conditions. Under alkaline conditions, a pH-dependent mixture of ¹HNO and ³NO⁻ was formed from the decomposition of Piloty’s acid. ³NO⁻ itself is a good reductant, and a reaction of ³NO⁻ and hydroxycobalamin was observed. Furthermore, ³NO⁻ reacts with the product of the reaction between hydroxycobalamin and ¹HNO/³NO⁻ namely nitroxylcobalamin
Homer Simpson Ponders Politics: Popular Culture as Political Theory
No full textIt is often said that the poet Homer “educated” ancient Greece. Joseph J. Foy and Timothy M. Dale have assembled a team of notable scholars who argue, quite persuasively, that Homer Simpson and his ilk are educating America and offering insights into the social order and the human condition.
Following Homer Simpson Goes to Washington (winner of the John G. Cawelti Award for Best Textbook or Primer on American and Popular Culture) and Homer Simpson Marches on Washington, this exceptional volume reveals how books like J. R. R. Tolkien’s The Hobbit and J. K. Rowling’s Harry Potter, movies like Avatar and Star Wars, and television shows like The Office and Firefly define Americans’ perceptions of society. The authors expand the discussion to explore the ways in which political theories play out in popular culture.
Homer Simpson Ponders Politics includes a foreword by fantasy author Margaret Weis (coauthor/creator of the Dragonlance novels and game world) and is divided according to eras and themes in political thought: The first section explores civic virtue, applying the work of Plato and Aristotle to modern media. Part 2 draws on the philosophy of Hobbes, Locke, Rousseau, and Smith as a framework for understanding the role of the state. Part 3 explores the work of theorists such as Kant and Marx, and the final section investigates the ways in which movies and newer forms of electronic media either support or challenge the underlying assumptions of the democratic order. The result is an engaging read for undergraduate students as well as anyone interested in popular culture.
Joseph J. Foy, associate campus dean and associate professor of political science at the University of Wisconsin–Waukesha, is the editor of Homer Simpson Goes to Washington: American Politics through Popular Culture and coeditor of Homer Simpson Marches on Washington: Dissent through American Popular Culture.
Timothy M. Dale, assistant professor of political science at the University of Wisconsin–La Crosse, is coeditor of Homer Simpson Marches on Washington: Dissent through American Popular Culture.
“Today, film, fiction, and television reflect our notions of civic virtue, morality, and the human condition—or at least help us to struggle with understanding and defining these. The ubiquitous nature of popular culture means that it will have an effect upon us, whether one likes that or not. The authors argue that, given this fact, even those who doubt the ‘seriousness’ of popular culture would do well to pay attention to it.”—Margaret Ferguson, Assistant Vice President for Statewide Academic Relations at Indiana University
Since ancient times myths and stories have been used to convey our deepest thoughts about how to live together in community. With this book we now have a fun and engaging way to learn and think about political theory through the myths and stories of our time, popular culture. -- William Irwin, author of Black Sabbath and Philosophy: Mastering Reality
Foy and Dale have done it again, this time with political theory! Political theory is one of the most difficult subjects that political science undergraduates encounter and Homer Simpson Ponders Politics opens up an avenue for students to engage many of the broad theories through some of the cultural artifacts with which they are most familiar: popular culture. These important theories bubble up through all areas of popular culture from Machiavelli and The Godfather to Plato and Star Wars— there is much to learn from this compendium. This is a useful book for students of political theory of any age or training and for those who are intrigued by the many political concepts popular culture teaches us. --Lilly J. Goren, coeditor of Women and the White House: Gender, Popular Culture, and Presidential Politics
Most essays in this collection employ their philosophical guides in ways that can...disabuse undergraduates of the notion that political theory can better address the sterile and obsolete concerns of forgotten eras than fundamental questions about contemporary political life. -- Choicehttps://uknowledge.uky.edu/upk_american_popular_culture/1013/thumbnail.jp
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