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  • 1
    Electronic Resource
    Electronic Resource
    Ring opening during the cationic polymerization of 2-methylene-1,3-dioxepane: Cyclic ketene acetal initiation with sulfuric acid supported on carbonSee Reference 1. (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 485-491 
    Details
    ISSN: 0887-624X
    Keywords: 2-methylene-1,3-dioxepane ; cyclic ketene acetal ; cationic polymerization ; activated carbon black ; 1,2-polymerization ; ring-opening polymerization ; ring-retained polymerization ; initiator ; catalyst ; heterogeneous catalysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The stable cyclic ketene acetal, 2-methylene-1,3-dioxepane, 7, has been polymerized cationically in pentane, CH2Cl2 and THF at 25°C to form a polymer which is composed of both ring-opened (40-50%) and ring-retained (50-60%) structures. Initiation was catalyzed by using H2SO4-supported on activated carbon black. This unique outcome differs significantly from the cationic polymerization of several other five- and six-membered ring cyclic ketene acetals which gave 100% 1,2-vinylpolymerization under these conditions. As the polymerization temperature increased in cationic polymerization of 7 the ring-opened content increased and the molecular weight of the polymers decreased in such solvents as cyclohexane, 1,2-dichloroethane, dimethoxyethane, and bis-(2-methoxyethyl) ether. The mechanism of this polymerization is discussed. This research also illustrated the ability to initiate the cationic polymerization of cyclic ketene acetals by acidified carbon black while avoiding subsequent polymer decomposition. © 1997 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Cationic copolymerization of cyclic ketene acetals: The effect of substituents on reactivity (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 861-871 
    Details
    ISSN: 0887-624X
    Keywords: 2-methylene-1,3-dioxane ; 4-methyl-2-methylene-1,3-dioxane ; 4,4,6-trimethyl-2-methylene-1,3-dioxane ; 2-methylene-1,3-dioxolane ; 4-methyl-2-methylene-1,3-dioxolane ; 4,5-dimethyl-2-methylene-1,3-dioxolane ; cationic copolymerization ; reactivity ratio ; relative reactivity ; ring-retained polymerization ; cyclic ketene acetals ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cationic copolymerizations of 4-methyl-2-methylene-1,3-dioxane, 2 (M1), with 2-methylene-1,3-dioxane, 1 (M2); of 4,4,6-trimethyl-2-methylene-1,3-dioxane, 3 (M1), with 2-methylene-1,3-dioxane, 1 (M2); of 4-methyl-2-methylene-1,3-dioxolane, 5 (M1), with 2-methylene-1,3-dioxolane, 4 (M2); and of 4,5-dimethyl-2-methylene-1,3-dioxolane, 6 (M1), with 2-methylene-1,3-dioxolane, 4 (M2) were conducted. The reactivity ratios for these four types of copolymerizations were r1 = 1.73 and r2 = 0.846; r1 = 2.26 and r2 = 0.310; r1 = 1.28 and r2 = 0.825; r1 = 2.23 and r2 = 0.515, respectively. The relative reactivities of these monomers towards cationic polymerization are: 3 〉 2 〉 1; and 6 〉 5 〉 4. With both five- and six-membered ring cyclic ketene acetals, the reactivity increased with increasing methyl substitution on the ring. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 861-871, 1998
    Additional Material: 6 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    BF3·OEt2-initiated polymerization of 2-methylene-1,3-dioxepanes (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 873-881 
    Details
    ISSN: 0887-624X
    Keywords: 2-methylene-1,3-dioxepane ; 4,7-dimethyl-2-methylene-1,3-dioxepane ; cyclic ketene acetal ; cationic polymerization ; ring-opening polymerization ; ring-retained polymerization ; copolymerization ; boron trifluoride etherate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: BF3·OEt2-initiated polymerizations of 2-methylene-1,3-dioxepane gave polymers composed of both ring-retained and ring-opened structures. The ring-opening content increased with an increase in polymerization temperature. Poly(4,7-dimethyl-2-methylene-1,3-dioxepane) propagated slower during BF3·OEt2-initiated polymerization and had a lower ring-opened content than poly(2-methylene-1,3-dioxepane). The type of acid initiator used also affected the amount of ring opening observed. Stronger acids gave less ring opening. Attempted BF3·OEt2-initiated copolymerizations of these seven-membered ring cyclic ketene acetals with isobutyl vinyl ether at room temperature resulted in formation of the two homopolymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 873-881, 1998
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    XPS/ISS Investigation of Carbon Fibers Sequentially Exposed to Nitric Acid and Sodium Hydroxide (1996)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 24 (1996), S. 311-320 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Type II carbon fibers have been oxidized to various extents in nitric acid, both with and without subsequent exposure to aqueous sodium hydroxide, and the resulting surface composition has been determined using angle-resolved x-ray photoelectron spectroscopy (ARXPS) and ion scattering spectroscopy (ISS). As-received fibers (unsized and commercially treated) contain substantial amounts of oxidized carbon, most of which is confined within the outermost 10-15 Å of the surface. Fiber treatment in 70% nitric acid at 115°C for 20-90 min alters the O/C atomic ratio as well as the depth distribution of oxidized carbon species. Evidence is presented suggesting that the fibers are oxidized primarily within the outermost surface region when the nitric acid exposure time is 〈40 min. As nitric acid treatment time is increased to 60 and 90 min, the fiber subsurface region near the maximum XPS sampling depth (60-100 Å) appears to be increasingly oxidized relative to further oxidation at the outermost surface region. This subsurface region is mostly the outer few graphitic layers which are exposed by pitting and roughening of the surface as oxidation continues. Exposing the nitric acid-oxidized carbon fibers to aqueous sodium hydroxide removes oxidized fragments from the outer fiber layers and consequently alters the depth profile of carbon/oxygen chemical groups. In most cases, after fiber exposure to sodium hydroxide, the relative O/C atomic ratio decreases by ∽10%, consistent with the removal of oxidized fiber fragments. Furthermore, ISS reveals that sodium hydroxide exposure enriches the outermost fiber layers with sodium, the concentration of which increases with increasing extent of prior nitric acid oxidation.
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  • 5
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    Disulphide-reduced psoriasin is a human apoptosis-inducing broad-spectrum fungicide (2015)
    National Academy of Sciences
    Details
    Publication Date: 2015-10-05
    Description: The unexpected resistance of psoriasis lesions to fungal infections suggests local production of an antifungal factor. We purified Trichophyton rubrum-inhibiting activity from lesional psoriasis scale extracts and identified the Cys-reduced form of S100A7/psoriasin (redS100A7) as a principal antifungal factor. redS100A7 inhibits various filamentous fungi, including the mold Aspergillus fumigatus, but not Candida albicans. Antifungal activity was inhibited by Zn2+, suggesting that redS100A7 interferes with fungal zinc homeostasis. Because S100A7-mutants lacking a single cysteine are no longer antifungals, we hypothesized that redS100A7 is acting as a Zn2+-chelator. Immunogold electron microscopy studies revealed that it penetrates fungal cells, implicating possible intracellular actions. In support with our hypothesis, the cell-penetrating Zn2+-chelator TPEN was found to function as a broad-spectrum antifungal. Ultrastructural analyses of redS100A7-treated T. rubrum revealed marked signs of apoptosis, suggesting that its mode of action is induction of programmed cell death. TUNEL, SYTOX-green analyses, and caspase-inhibition studies supported this for both T. rubrum and A. fumigatus. Whereas redS100A7 can be generated from oxidized S100A7 by action of thioredoxin or glutathione, elevated redS100A7 levels in fungal skin infection indicate induction of both S100A7 and its reducing agent in vivo. To investigate whether redS100A7 and TPEN are antifungals in vivo, we used a guinea pig tinea pedes model for fungal skin infections and a lethal mouse Aspergillus infection model for lung infection and found antifungal activity in both in vivo animal systems. Thus, selective fungal cell-penetrating Zn2+-chelators could be useful as an urgently needed novel antifungal therapeutic, which induces programmed cell death in numerous fungi.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 6
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    A polysaccharide-degrading marine bacterium Flammeovirga sp. MY04 and its extracellular agarase system (2012)
    Springer
    Details
    Publication Date: 2012-07-24
    Print ISSN: 1672-5182
    Electronic ISSN: 1993-5021
    Topics: Geosciences
    Published by Springer
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  • 7
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    Sensors, Vol. 19, Pages 3431: A Hybrid Two-Axis Force Sensor for the Mesoscopic Structural Superlubricity Studies (2019)
    MDPI
    In: Sensors
    Details
    Publication Date: 2019
    Description: Structural superlubricity (SSL) is a state of nearly zero friction and zero wear between two directly contacted solid surfaces. Recently, SSL was achieved in mesoscale and thus opened the SSL technology which promises great applications in Micro-electromechanical Systems (MEMS), sensors, storage technologies, etc. However, load issues in current mesoscale SSL studies are still not clear. The great challenge is to simultaneously measure both the ultralow shear forces and the much larger normal forces, although the widely used frictional force microscopes (FFM) and micro tribometers can satisfy the shear forces and normal forces requirements, respectively. Here we propose a hybrid two-axis force sensor that can well fill the blank between the capabilities of FFM and micro tribometers for the mesoscopic SSL studies. The proposed sensor can afford 1mN normal load with 10 nN lateral resolution. Moreover, the probe of the sensor is designed at the edge of the structure for the convenience of real-time optical observation. Calibrations and preliminary experiments are conducted to validate the performance of the design.
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Published by MDPI
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  • 8
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    Highly hydrophilic and anti-fouling cellulose thin film composite membrane based on the hierarchical poly(vinyl alcohol-co-ethylene) nanofiber substrate (2015)
    Springer
    Details
    Publication Date: 2015-06-16
    Print ISSN: 0969-0239
    Electronic ISSN: 1572-882X
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Published by Springer
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  • 9
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    Characteristic Modeling and Control of Servo Systems with Backlash and Friction (2014)
    Hindawi
    Details
    Publication Date: 2014-02-20
    Description: A novel approach for modeling and control of servo systems with backlash and friction is proposed based on the characteristic model. Firstly, to deal with friction-induced nonlinearities, a smooth Stribeck friction model is introduced. The backlash is modeled by a continuous and derivable mathematical function. Secondly, a characteristic model in the form of a second-order slowly time-varying difference equation is established and verified by simulations. Thirdly, a composite controller including the golden-section adaptive control law and the integral control law is designed and the stability of the closed-loop system is analyzed. The simulation and experimental results show that the proposed control scheme is effective and can improve the steady-state precision and the dynamic performance of the servo system with backlash and friction.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 10
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    Multiple Shape Transformations of Composite Hydrogel Sheets (2013)
    American Chemical Society (ACS)
    Details
    Publication Date: 2013-03-16
    Description: Journal of the American Chemical Society DOI: 10.1021/ja400518c
    Print ISSN: 0002-7863
    Electronic ISSN: 1520-5126
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society (ACS)
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