511 research outputs found

    Surface Structure of Tetrahedral-Coordinated Amorphous Diamond-Like Carbon Films Grown by Pulsed Laser Deposition

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    The structure and composition of tetrahedral-coordinated amorphous diamond-like carbon films (a-tC) grown by pulsed laser deposition (PLD) of graphite has been studied with atomic force microscopy (AFM). The nanometer-scale surface structure has been studied as a function of growth parameters (e.g., laser energy density and film thickness) using contact-mode and tapping-mode AFM. Although the surfaces were found to be generally smooth, they exhibited reproducible structural features on several size scales which correlate with the variation of laser energy and th excited ion etching

    Measurement of the vector analyzing power in elastic electron-proton scattering as a probe of double photon exchange amplitudes

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    We report the first measurement of the vector analyzing power in inclusive transversely polarized elastic electron-proton scattering at Q^2 = 0.1 (GeV/c)^2 and large scattering angles. This quantity should vanish in the single virtual photon exchange, plane wave impulse approximation for this reaction, and can therefore provide information on double photon exchange amplitudes for electromagnetic interactions with hadronic systems. We find a non-zero value of A=-15.4+/-5.4 ppm. No calculations of this observable for nuclei other than spin 0 have been carried out in these kinematics, and the calculation using the spin orbit interaction from a charged point nucleus of spin 0 cannot describe these data.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let

    Nonequilibrium wetting

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    When a nonequilibrium growing interface in the presence of a wall is considered a nonequilibrium wetting transition may take place. This transition can be studied trough Langevin equations or discrete growth models. In the first case, the Kardar-Parisi-Zhang equation, which defines a very robust universality class for nonequilibrium moving interfaces, with a soft-wall potential is considered. While in the second, microscopic models, in the corresponding universality class, with evaporation and deposition of particles in the presence of hard-wall are studied. Equilibrium wetting is related to a particular case of the problem, it corresponds to the Edwards-Wilkinson equation with a potential in the continuum approach or to the fulfillment of detailed balance in the microscopic models. In this review we present the analytical and numerical methods used to investigate the problem and the very rich behavior that is observed with them.Comment: Review, 36 pages, 16 figure

    Wetting films on chemically heterogeneous substrates

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    Based on a microscopic density functional theory we investigate the morphology of thin liquidlike wetting films adsorbed on substrates endowed with well-defined chemical heterogeneities. As paradigmatic cases we focus on a single chemical step and on a single stripe. In view of applications in microfluidics the accuracy of guiding liquids by chemical microchannels is discussed. Finally we give a general prescription of how to investigate theoretically the wetting properties of substrates with arbitrary chemical structures.Comment: 56 pages, RevTeX, 20 Figure

    Towards Machine Wald

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    The past century has seen a steady increase in the need of estimating and predicting complex systems and making (possibly critical) decisions with limited information. Although computers have made possible the numerical evaluation of sophisticated statistical models, these models are still designed \emph{by humans} because there is currently no known recipe or algorithm for dividing the design of a statistical model into a sequence of arithmetic operations. Indeed enabling computers to \emph{think} as \emph{humans} have the ability to do when faced with uncertainty is challenging in several major ways: (1) Finding optimal statistical models remains to be formulated as a well posed problem when information on the system of interest is incomplete and comes in the form of a complex combination of sample data, partial knowledge of constitutive relations and a limited description of the distribution of input random variables. (2) The space of admissible scenarios along with the space of relevant information, assumptions, and/or beliefs, tend to be infinite dimensional, whereas calculus on a computer is necessarily discrete and finite. With this purpose, this paper explores the foundations of a rigorous framework for the scientific computation of optimal statistical estimators/models and reviews their connections with Decision Theory, Machine Learning, Bayesian Inference, Stochastic Optimization, Robust Optimization, Optimal Uncertainty Quantification and Information Based Complexity.Comment: 37 page

    Primary ciliary dyskinesia: Longitudinal study of lung disease by ultrastructure defect and genotype

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    Rationale: In primary ciliary dyskinesia, factors leading to disease heterogeneity are poorly understood. Objectives: To describe early lung disease progression in primary ciliary dyskinesia and identify associations between ultrastructural defects and genotypes with clinical phenotype. Methods: This was a prospective, longitudinal (5 yr), multicenter, observational study. Inclusion criteria were less than 19 years at enrollment and greater than or equal to two annual study visits. Linear mixed effects models including random slope and random intercept were used to evaluate longitudinal associations between the ciliary defect group (or genotype group) and clinical features (percent predicted FEV 1 and weight and height z-scores). Measurements and Main Results: A total of 137 participants completed 732 visits. The group with absent inner dynein arm, central apparatus defects, and microtubular disorganization (IDA/CA/MTD) (n = 41) were significantly younger at diagnosis and in mixed effects models had significantly lower percent predicted FEV 1 and weight and height z-scores than the isolated outer dynein arm defect (n = 55) group. Participants with CCDC39 or CCDC40 mutations (n = 34) had lower percent predicted FEV 1 and weight and height z-scores than those with DNAH5 mutations (n = 36). For the entire cohort, percent predicted FEV 1 decline was heterogeneous with a mean (SE) decline of 0.57 (0.25) percent predicted/yr. Rate of decline was different from zero only in the IDA/MTD/CA group (mean [SE], 21.11 [0.48] percent predicted/yr; P = 0.02). Conclusions: Participants with IDA/MTD/CA defects, which included individuals with CCDC39 or CCDC40 mutations, had worse lung function and growth indices compared with those with outer dynein arm defects and DNAH5 mutations, respectively. The only group with a significant lung function decline over time were participants with IDA/MTD/CA defects

    Photoproduction of D±D^{*\pm} mesons associated with a leading neutron

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    The photoproduction of D±(2010)D^{*\pm} (2010) mesons associated with a leading neutron has been observed with the ZEUS detector in epep collisions at HERA using an integrated luminosity of 80 pb1^{-1}. The neutron carries a large fraction, {xL>0.2x_L>0.2}, of the incoming proton beam energy and is detected at very small production angles, {θn<0.8\theta_n<0.8 mrad}, an indication of peripheral scattering. The DD^* meson is centrally produced with pseudorapidity {η1.9|\eta| 1.9 GeV}, which is large compared to the average transverse momentum of the neutron of 0.22 GeV. The ratio of neutron-tagged to inclusive DD^* production is 8.85±0.93(stat.)0.61+0.48(syst.)%8.85\pm 0.93({\rm stat.})^{+0.48}_{-0.61}({\rm syst.})\% in the photon-proton center-of-mass energy range {130<W<280130 <W<280 GeV}. The data suggest that the presence of a hard scale enhances the fraction of events with a leading neutron in the final state.Comment: 28 pages, 4 figures, 2 table

    Comedy in Unfunny Times: News Parody and Carnival after 9/11

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    Comedy has a special role in helping societies manage crisis moments, and the U.S. media paid considerable attention to the proper role of comedy in public culture after the 9/11 tragedies. As has been well documented, many popular U.S. comic voices were paralyzed in trying to respond to 9/11 or disciplined by audiences when they did. Starting with these obstacles in mind, this essay analyzes early comic responses to 9/11, and particularly those of the print and online news parody The Onion, as an example of how “fake” news discourse could surmount the rhetorical chill that fell over public culture after the tragedies. By exposing the news as “mere” production and by setting an agenda for learning about Islamic culture and Middle East politics, The Onion avoided violating decorum and invited citizen participation. This kind of meta-discourse was crucial after 9/11, when shifting rules for decorum created controversy and as official voices in government and media honed frames and narratives for talking about the attacks
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