Stability for quasi-periodically perturbed Hill's equations

We consider a perturbed Hill's equation of the form $\ddot \phi + (p_{0}(t) + \epsilon p_{1}(t)) \phi = 0$, where $p_{0}$ is real analytic and periodic, $p_{1}$ is real analytic and quasi-periodic and \eps is a ``small'' real parameter. Assuming Diophantine conditions on the frequencies of the decoupled system, i.e. the frequencies of the external potentials $p_{0}$ and $p_{1}$ and the proper frequency of the unperturbed ($\epsilon=0$) Hill's equation, but without making non-degeneracy assumptions on the perturbing potential $p_{1}$, we prove that quasi-periodic solutions of the unperturbed equation can be continued into quasi-periodic solutions if $\epsilon$ lies in a Cantor set of relatively large measure in $[-\epsilon_0,\epsilon_0]$, where $\epsilon_0$ is small enough. Our method is based on a resummation procedure of a formal Lindstedt series obtained as a solution of a generalized Riccati equation associated to Hill's problem.Comment: 40 pages, 4 figure

Structural Game Characteristics and Problematic Gaming:Introduction of the Risk Characteristics Checklist for Games (RCCG)

Introduction: The current state of research suggests that personal, environmental, and product-related risk factors contribute to the development and maintenance of gaming disorder. Concerning game related risk factors, evidence points to certain game features contributing to the overall risk of gaming disorder, as for example reward features, social features, and monetization features. However, no standardized instrument is available to capture risk enhancing game characteristics. Methods: Based on theoretical considerations and stepwise conducted qualitative analyses of in-game content, risk-enhancing game features were identified and specified. Furthermore, a pilot study was conducted comprising N = 4,468 students (M[Age] = 14.54 years, SD = 1.37 years). Game features of the preferred games of the students were analyzed regarding their predictive value of gaming disorder. Results: Data suggests that two features are associated most strongly with gaming disorder: 1) mandatory social interactions (β = .20), and 2) number of reward categories (β = .12). Based on these findings and further updates, the RCCG was refined and finalized. Conclusions: With the RCCG, a structured instrument to capture, describe, and evaluate risk enhancing structural characteristics of video games is available. The RCCG enables a general risk assessment of games as well as recommended age-classifications based on certain structural features unsuitable for specific age groups

Lilith: A scalable secure tool for massively parallel distributed computing

Changes in high performance computing have necessitated the ability to utilize and interrogate potentially many thousands of processors. The ASCI (Advanced Strategic Computing Initiative) program conducted by the United States Department of Energy, for example, envisions thousands of distinct operating systems connected by low-latency gigabit-per-second networks. In addition multiple systems of this kind will be linked via high-capacity networks with latencies as low as the speed of light will allow. Code which spans systems of this sort must be scalable; yet constructing such code whether for applications, debugging, or maintenance is an unsolved problem. Lilith is a research software platform that attempts to answer these questions with an end toward meeting these needs. Presently, Lilith exists as a test-bed, written in Java, for various spanning algorithms and security schemes. The test-bed software has, and enforces, hooks allowing implementation and testing of various security schemes

Bringing Empathy into Play: On the Effects of Empathy in Violent and Nonviolent Video Games

While violent media has adverse effects on cognition, emotion and behavior, prosocial content promotes these variables in a prosocial way. Greater individual levels of empathy as well as increasing the level of empathy in media content typically foster prosocial behavior and reduce aggression. Two experiments replicated game content findings, and also showed that inducing empathy prior to a video game had a positive influence on behavior. However, under certain circumstances, inducing empathy before playing a violent video game may even have negative effects on behavior. As empathy is a common tool in prevention programs, the implications of these findings are discussed

Poly(vinylidene fluoride) and copolymers as porous membranes for tissue engineering applications

Poly(vinylidene fluoride) (PVDF) and its main copolymers - poly(vinylidene fluoride-co-hexafluoropropene), P(VDF-HFP), and poly(vinylidene fluoride-co-trifluoroethylene), P(VDF-TrFE) - were processed by solvent casting at room temperature in the form of porous membranes. Copolymer membranes showed higher degree of porosity than PVDF, the average pore size being larger for P(VDF-TrFE) than for P(VDF-HFP) and PVDF. All membranes show high hydrophobicity with water contact angles in the range 94° to 115°, and electroactive beta phase contents above 90%. The adhesion and proliferation of both C2C12 myoblast and MC3T3-E1 pre-osteoblast cells on the membranes were investigated. It is demonstrated that PVDF membranes promote higher cell proliferation while P(VDF-HFP) membranes show the lowest proliferation for both kinds of cell. The proliferation on P(VDF-TrFE) membranes is cell dependent, higher for MC3T3-E1 cells but lower for C2C12 cells, related to the effect of the highly porous structure on the preferred morphology of each cell type, as the higher pore size and porosity of the P(VDF-TrFE) membrane induce cell elongation, which is preferred just by the C2C12 muscle cells.Funded by FEDER funds through the “Programa Operacional Fatores de Competitividade e COMPETE” and by national funds arranged by FCT Fundação para a Ciência e a Tecnologia, project references PTDC/CTM-NAN/112574/2009 and PEST-C/FIS/UI607/2014. Funding from “MateproOptimizing Materials and Processes”, ref. NORTE-07-0124-FEDER-000037”, co-funded by the “Programa Operacional Regional do Norte” (ON.2 e O Novo Norte), under the “Quadro de Referência Estrategico Nacional” (QREN), through the “Fundo Europeu de Desenvolvimento Regional” (FEDER). FCT for the SFRH/BPD/90870/2012 grant

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Measurement of D*+/- meson production in jets from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

This paper reports a measurement of D*+/- meson production in jets from proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb^-1 for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range |eta| < 2.5. D*+/- mesons found in jets are fully reconstructed in the decay chain: D*+ -> D0pi+, D0 -> K-pi+, and its charge conjugate. The production rate is found to be N(D*+/-)/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*+/- mesons that carry a fraction z of the jet momentum in the range 0.3 < z < 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.Comment: 10 pages plus author list (22 pages total), 5 figures, 1 table, matches published version in Physical Review