408 research outputs found

    On ordinal utility, cardinal utility, and random utility  

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    Though the Random Utility Model (RUM) was conceived  entirely in terms of ordinal utility, the apparatus throughwhich it is widely practised exhibits properties of  cardinal utility.  The adoption of cardinal utility as a  working operation of ordinal is perfectly valid, provided  interpretations drawn from that operation remain faithful  to ordinal utility.  The paper considers whether the latterrequirement holds true for several measurements commonly  derived from RUM.  In particular it is found that  measurements of consumer surplus change may depart from  ordinal utility, and exploit the cardinality inherent in  the practical apparatus.

    Plasma polymerization of isopentyl nitrite at atmospheric pressure: gas phase analysis and surface chemistry

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    Nitric oxide (NO)-releasing coatings have promising potential for biomedical applications notably in implant safety and wound dressing by promoting healing and reducing bacterial growth. Yet, the production of NO-films remains difficult through classic approaches. In this study, plasma polymerized NO-coatings are produced using a helium-isopentyl nitrite mixture under two power settings and deposited on aluminum samples. Analyses of the plasma phase by mass spectroscopy reveal the presence of nitrosoxy groups (O–N═O) in monomer and quasi-monomer at low power, and a higher fragmentation rate at high power. Static and no-static samples are made and analyzed by X-ray photoelectron spectroscopy showing the presence of these group for both power conditions, with a better retention on the sample's center for the latest

    Plasma polymerization of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl in a collisional, capacitively coupled radio frequency discharge

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    Plasma polymerization of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) yields thin films containing stable nitroxide radicals that have properties analogous to that of nitric oxide (NO) without short lifetimes. This property gives TEMPO films a wide variety of potential applications. Typically, control of the final film chemistry is difficult and the plasma discharge conditions must be tailored to in order to maximize the retention of these nitroxide groups during the polymerization and deposition process. In this study, plasma diagnostics and surface analysis of the deposited films were carried out to determine the optimal plasma conditions for the retention of nitroxide groups. These techniques included energy-resolved mass spectrometry, heated planar probe ion current measurements, deposition rate measurements, and x-ray photoelectron spectroscopy (XPS). Results show that operating the plasma with a combination of low input powers and high pressures produces a collisional discharge in which fragmentation of the TEMPO molecule is suppressed, leading to good retention of nitroxide groups. Ion energy distribution functions and quartz crystal microbalance measurements support the soft landing theory of ion deposition on the substrate within this γ-mode, in which the flux of low energy, soft landed ions form the primary contribution to film growth. XPS analysis of deposited polymers shows 75.7% retention of N - O groups in the polymer films deposited in a 25 Pa 5 W discharge. © 2020 Author(s)

    Optimization of the high-throughput synthesis of multiblock copolymer nanoparticles in aqueous media: Via polymerization-induced self-assembly

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    Over the past fifteen years or so, polymerization-induced self-assembly (PISA) has become widely recognized as a powerful and versatile platform technology for the synthesis of a wide range of block copolymer nanoparticles of controlled size, shape and surface chemistry. In the present study, we report that PISA formulations are sufficiently robust to enable high-throughput experiments using a commercial synthesis robot (Chemspeed Autoplant A100). More specifically, we use reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerization of either n-butyl methacrylate and/or benzyl methacrylate to prepare various examples of methacrylic multiblock copolymer nanoparticles using a poly(methacrylic acid) stabilizer block. Adequate stirring is essential to generate sufficiently small monomer droplets for such heterogeneous polymerizations to proceed efficiently. Good reproducibility can be achieved under such conditions, with well-defined spherical morphologies being obtained at up to 45% w/w solids. GPC studies indicate high blocking efficiencies but relatively broad molecular weight distributions (Mw/Mn= 1.36-1.85), suggesting well-defined (albeit rather polydisperse) block copolymer chains. These preliminary studies provide a sound basis for high-throughput screening of RAFT-mediated PISA formulations, which is likely to be required for commercialization of this technology. Our results indicate that methacrylic PISA formulations enable the synthesis of diblock and triblock copolymer nanoparticles in high overall yield (94-99%) within 1-3 h at 70 °C. However, tetrablocks suffer from incomplete conversions (87-96% within 5 h) and hence most likely represent the upper limit for this approach

    Solution and Solid-State Behavior of Amphiphilic ABA Triblock Copolymers of Poly(acrylic acid-stat-styrene)-block-poly(butyl acrylate)-block-poly(acrylic acid-stat-styrene)

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    A combination of statistical and triblock copolymer properties is explored to produce stable aqueous polymer dispersions suitable for the film formation. In order to perform an extensive structural characterization of the products in the dissolved, dispersed, and solid states, a wide range of symmetrical poly(acrylic acid-stat-styrene)x-block-poly(butyl acrylate)y-block-poly(acrylic acid-stat-styrene)x, poly(AA-st-St)x-b-PBAy-b-poly(AA-st-St)x, (x = 56, 108 and 140, y = 100–750; the AA:St molar ratio is 42:58) triblock copolymers were synthesized by reversible addition–fragmentation chain transfer (RAFT) solution polymerization using a bifunctional symmetrical RAFT agent. It is demonstrated that the amphiphilic statistical outer blocks can provide sufficient stabilization to largely hydrophobic particles in aqueous dispersions. Such a molecular design provides an advantage over copolymers composed only of homoblocks, as a simple variation of the statistical block component ratio provides an efficient way to control the hydrophilicity of the stabilizer block, which ultimately affects the copolymer morphology in solutions and solid films. It was found by small-angle X-ray scattering (SAXS) that the copolymers behaved as dissolved chains in methylethylketone (MEK) but self-assembled in water into stable and well-defined spherical particles that increased in size with the length of the hydrophobic PBA block. These particles possessed an additional particulate surface structure formed by the statistical copolymer stabilizer block, which self-folded through the hydrophobic interactions between the styrene units. SAXS and atomic force microscopy showed that the copolymer films cast from the MEK solutions formed structures predicted by self-consistent field theory for symmetrical triblock copolymers, while the aqueous dispersions formed structural morphologies similar to a close-packed spheres, as would be expected for copolymer particles trapped kinetically due to the restricted movement of the blocks in the initial aqueous dispersion. A strong correlation between the structural morphology and mechanical properties of the films was observed. It was found that the properties of the solvent cast films were highly dependent on the ratios of the hard [poly(AA-st-St)] and soft (PBA) blocks, while the aqueous cast films did not show such a dependence. The continuous phase of hard blocks, always formed in the case of the aqueous cast films, produced films with a higher elastic modulus and a lower extension-to-break in a comparison with the solvent-cast films

    A complete 3D numerical study of the effects of pseudoscalar-photon mixing on quasar polarizations

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    We present the results of three-dimensional simulations of quasar polarizations in the presence of pseudoscalar-photon mixing in the intergalactic medium. The intergalactic magnetic field is assumed to be uncorrelated in wave vector space but correlated in real space. Such a field may be obtained if its origin is primordial. Furthermore we assume that the quasars, located at cosmological distances, have negligible initial polarization. In the presence of pseudoscalar-photon mixing we show, through a direct comparison with observations, that this may explain the observed large scale alignments in quasar polarizations within the framework of big bang cosmology. We find that the simulation results give a reasonably good fit to the observed data.Comment: 15 pages, 8 figures, significant changes, to appear in EPJ

    A Phenomenological Analysis of Gluon Mass Effects in Inclusive Radiative Decays of the J/ψ\rm{J/\psi} and $\Upsilon

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    The shapes of the inclusive photon spectra in the processes \Jp \to \gamma X and \Up \to \gamma X have been analysed using all available experimental data. Relativistic, higher order QCD and gluon mass corrections were taken into account in the fitted functions. Only on including the gluon mass corrections, were consistent and acceptable fits obtained. Values of 0.7210.068+0.0160.721^{+0.016}_{-0.068} GeV and 1.180.29+0.091.18^{+0.09}_{-0.29} GeV were found for the effective gluon masses (corresponding to Born level diagrams) for the \Jp and \Up respectively. The width ratios \Gamma(V \to {\rm hadrons})/\Gamma(V \to \gamma+ {\rm hadrons}) V=\Jp, \Up were used to determine αs(1.5GeV)\alpha_s(1.5 {\rm GeV}) and αs(4.9GeV)\alpha_s(4.9 {\rm GeV}). Values consistent with the current world average αs\alpha_s were obtained only when gluon mass correction factors, calculated using the fitted values of the effective gluon mass, were applied. A gluon mass 1\simeq 1 GeV, as suggested with these results, is consistent with previous analytical theoretical calculations and independent phenomenological estimates, as well as with a recent, more accurate, lattice calculation of the gluon propagator in the infra-red region.Comment: 50 pages, 11 figures, 15 table

    Quantum Vacuum Experiments Using High Intensity Lasers

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    The quantum vacuum constitutes a fascinating medium of study, in particular since near-future laser facilities will be able to probe the nonlinear nature of this vacuum. There has been a large number of proposed tests of the low-energy, high intensity regime of quantum electrodynamics (QED) where the nonlinear aspects of the electromagnetic vacuum comes into play, and we will here give a short description of some of these. Such studies can shed light, not only on the validity of QED, but also on certain aspects of nonperturbative effects, and thus also give insights for quantum field theories in general.Comment: 9 pages, 8 figur

    An overview of jets and outflows in stellar mass black holes

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    In this book chapter, we will briefly review the current empirical understanding of the relation between accretion state and and outflows in accreting stellar mass black holes. The focus will be on the empirical connections between X-ray states and relativistic (`radio') jets, although we are now also able to draw accretion disc winds into the picture in a systematic way. We will furthermore consider the latest attempts to measure/order jet power, and to compare it to other (potentially) measurable quantities, most importantly black hole spin.Comment: Accepted for publication in Space Science Reviews. Also to appear in the Space Sciences Series of ISSI - The Physics of Accretion on to Black Holes (Springer Publisher
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