157 research outputs found

    Nonintegrability of the two-body problem in constant curvature spaces

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    We consider the reduced two-body problem with the Newton and the oscillator potentials on the sphere S2{\bf S}^{2} and the hyperbolic plane H2{\bf H}^{2}. For both types of interaction we prove the nonexistence of an additional meromorphic integral for the complexified dynamic systems.Comment: 20 pages, typos correcte

    LHC Transverse Feedback System and its Hardware Commissioning

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    A powerful transverse feedback system ("Damper") has been installed in LHC. It will stabilise coupled bunch instabilities in a frequency range from 3 kHz to 20 MHz and at the same time damp injection oscillations originating from steering errors and injection kicker ripple. The transverse damper can also be used as an exciter for purposes of abort gap cleaning or tune measurement. The power and lowlevel systems layouts are described along with results from the hardware commissioning. The achieved performance is compared with earlier predictions and requirements for injection damping and instability control

    LHC Transverse Feedback System: First Results of Commissionning

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    A powerful transverse feedback system ("Damper") has been installed in LHC. It will stabilise the high intensity beam against coupled bunch transverse instabilities in a frequency range from 3 kHz to 20 MHz and at the same time damp injection oscillations originating from steering errors and injection kicker ripple. The LHC Damper can also be used as means of exciting transverse oscillations for the purposes of abort gap cleaning and tune measurement. The LHC Damper includes 4 feedback systems on 2 circulating beams (in other words one feedback system per beam and plane). Every feedback system consists of 4 electrostatic kickers, 4 push-pull wide band power amplifiers, 8 preamplifiers, two digital processing units and 2 beam position monitors with low-level electronics. The power and low-level subsystem layout is described along with first results from the commissioning of 16 power amplifiers and 16 electrostatic kickers located in the LHC tunnel. The achieved performance is compared with earlier predictions and requirements for injection damping and instability control. Requirements and first measurements of the performance of the power and low-level subsystems are summarized

    Characteristic Energy of the Coulomb Interactions and the Pileup of States

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    Tunneling data on La1.28Sr1.72Mn2O7\mathrm{La_{1.28}Sr_{1.72}Mn_2O_7} crystals confirm Coulomb interaction effects through the E\sqrt{\mathrm{E}} dependence of the density of states. Importantly, the data and analysis at high energy, E, show a pileup of states: most of the states removed from near the Fermi level are found between ~40 and 130 meV, from which we infer the possibility of universal behavior. The agreement of our tunneling data with recent photoemission results further confirms our analysis.Comment: 4 pages, 4 figures, submitted to PR

    Developmental malformation of the corpus callosum: a review of typical callosal development and examples of developmental disorders with callosal involvement

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    This review provides an overview of the involvement of the corpus callosum (CC) in a variety of developmental disorders that are currently defined exclusively by genetics, developmental insult, and/or behavior. I begin with a general review of CC development, connectivity, and function, followed by discussion of the research methods typically utilized to study the callosum. The bulk of the review concentrates on specific developmental disorders, beginning with agenesis of the corpus callosum (AgCC)—the only condition diagnosed exclusively by callosal anatomy. This is followed by a review of several genetic disorders that commonly result in social impairments and/or psychopathology similar to AgCC (neurofibromatosis-1, Turner syndrome, 22q11.2 deletion syndrome, Williams yndrome, and fragile X) and two forms of prenatal injury (premature birth, fetal alcohol syndrome) known to impact callosal development. Finally, I examine callosal involvement in several common developmental disorders defined exclusively by behavioral patterns (developmental language delay, dyslexia, attention-deficit hyperactive disorder, autism spectrum disorders, and Tourette syndrome)

    Entry Mode Degree of Control, Firm Performance and Host Country Institutional Development: A Meta-Analysis

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    Among studies on performance outcomes of entry mode choices disagreement fueled by ambiguous research findings is apparent as regards whether the best per- formers are those firms that enter foreign countries with high or low entry mode degree of control. To solve this dilemma and test new hypotheses, the relationship between entry mode degree of control and firm performance is examined by meta- analyzing 133 studies (740,114 observations) covering entry mode choices from 1980 to 2010. We find that (a) overall high-control entry modes lead to higher per- formance, and (b) adopting high-control entry modes is particularly important for firms entering developing countries
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