4,577 research outputs found
Jacobi multipliers, non-local symmetries and nonlinear oscillators
Constants of motion, Lagrangians and Hamiltonians admitted by a family of
relevant nonlinear oscillators are derived using a geometric formalism. The
theory of the Jacobi last multiplier allows us to find Lagrangian descriptions
and constants of the motion. An application of the jet bundle formulation of
symmetries of differential equations is presented in the second part of the
paper. After a short review of the general formalism, the particular case of
non-local symmetries is studied in detail by making use of an extended
formalism. The theory is related to some results previously obtained by
Krasil'shchi, Vinogradov and coworkers. Finally the existence of non-local
symmetries for such two nonlinear oscillators is proved.Comment: 20 page
Magnetic permeability of ( Fe Co Ge ) 88 Zr 6 B 5 Cu 1 alloys: Thermal stability in a wide temperature range.
Temperature dependence, from room temperature up to 1000 K, of the initial permeability of
Fe83−xCoxGe5Zr6B5Cu1 x=5 and 20 alloys at different stages of devitrification is reported. As
nanocrystallization progresses, room temperature decreases but high temperature one increases,
leading to an improvement of its thermal stability extended from room temperature up to 915 K,
characterized by a temperature coefficient of permeability 0.1%/K 4000 and 0.04%/K
800 for 5 and 20 at. % Co containing alloys, respectively
(Non)local Hamiltonian and symplectic structures, recursions, and hierarchies: a new approach and applications to the N=1 supersymmetric KdV equation
Using methods of math.DG/0304245 and [I.S.Krasil'shchik and P.H.M.Kersten,
Symmetries and recursion operators for classical and supersymmetric
differential equations, Kluwer, 2000], we accomplish an extensive study of the
N=1 supersymmetric Korteweg-de Vries equation. The results include: a
description of local and nonlocal Hamiltonian and symplectic structures, five
hierarchies of symmetries, the corresponding hierarchies of conservation laws,
recursion operators for symmetries and generating functions of conservation
laws. We stress that the main point of the paper is not just the results on
super-KdV equation itself, but merely exposition of the efficiency of the
geometrical approach and of the computational algorithms based on it.Comment: 16 pages, AMS-LaTeX, Xy-pic, dvi-file to be processed by dvips. v2:
nonessential improvements of exposition, title change
Algebraic theories of brackets and related (co)homologies
A general theory of the Frolicher-Nijenhuis and Schouten-Nijenhuis brackets
in the category of modules over a commutative algebra is described. Some
related structures and (co)homology invariants are discussed, as well as
applications to geometry.Comment: 14 pages; v2: minor correction
Physics at a Fermilab Proton Driver
This report documents the physics case for building a 2 MW, 8 GeV
superconducting linac proton driver at Fermilab.Comment: 52 pages, 15 figure
Habitual Physical Activity After Total Knee Replacement:analysis in 830 patients and comparison with a sex-and age-matched normative population (vol 92, pg 1109, 2012)
Background. Previous studies on physical activity after total knee arthroplasty (TKA) concentrated mainly on a return to sports activities. Objective. The objectives of this study were to determine the habitual physical activity behavior of people who had undergone TKA (TKA group) 1 to 5 years after surgery and to examine to what extent they adhered to international guidelines for health-enhancing physical activity. Additional aims were to compare younger (= 65 years old) people as well as men and women in the TKA group and to compare the results for the TKA group with those for a sex- and age-matched normative population (normative group). Design. This investigation was a cohort study. Methods. All people who had a primary TKA at 1 of 2 participating hospitals between 2002 and 2006 were sent the Short Questionnaire to Assess Health-Enhancing Physical Activity at least 1 year after surgery. Results. The TKA group spent, on average, 1,347 minutes per week on physical activity, most of which was light-intensity activity (780 minutes per week). Participants younger than 65 years of age spent significantly more time on physical activity than participants 65 years of age or older. There was no significant difference between male and female participants. Compared with the sex- and age-matched normative group, the TKA group spent significantly less time on the total amount of physical activity per week and met the guidelines for health-enhancing physical activity less often (55% versus 64%). Limitations. A self-administered questionnaire was used to assess habitual physical activity, and presurgery data on physical activity were not available. Conclusions. Almost half of the TKA group did not meet the health-enhancing physical activity guidelines, and the TKA group was not as physically active as the normative group. People who have undergone TKA should be encouraged to be more physically active
Particles as probes for complex plasmas in front of biased surfaces
An interesting aspect in the research of complex (dusty) plasmas is the
experimental study of the interaction of micro-particles with the surrounding
plasma for diagnostic purposes. Local electric fields can be determined from
the behaviour of particles in the plasma, e.g. particles may serve as
electrostatic probes. Since in many cases of applications in plasma technology
it is of great interest to describe the electric field conditions in front of
floating or biased surfaces, the confinement and behaviour of test particles is
studied in front of floating walls inserted into a plasma as well as in front
of additionally biased surfaces. For the latter case, the behaviour of
particles in front of an adaptive electrode, which allows for an efficient
confinement and manipulation of the grains, has been experimentally studied in
dependence on the discharge parameters and on different bias conditions of the
electrode. The effect of the partially biased surface (dc, rf) on the charged
micro-particles has been investigated by particle falling experiments. In
addition to the experiments we also investigate the particle behaviour
numerically by molecular dynamics, in combination with a fluid and
particle-in-cell description of the plasma.Comment: 39 pages, 16 figures, submitted to New J. Phy
The Hardware of the ATLAS Pixel Detector Control System
The innermost part of the ATLAS (A Toroidal LHC ApparatuS) experiment will be a pixel detector, built of 1744 individual detector modules. To operate the modules, readout electronics, and other detector components, a complex power supply and control system is necessary. The specific powering and control requirements are described, along with the custom made components of our power supply and control systems. These include remotely programmable Regulator Stations, the power supply system for the optical transceivers, several monitoring units and the Interlock System
Towards constraints on the SUSY seesaw from flavour-dependent leptogenesis
We systematically investigate constraints on the parameters of the
supersymmetric type-I seesaw mechanism from the requirement of successful
thermal leptogenesis in the presence of upper bounds on the reheat temperature
of the early Universe. To this end, we solve the
flavour-dependent Boltzmann equations in the MSSM, extended to include
reheating. With conservative bounds on , leading to mildly
constrained scenarios for thermal leptogenesis, compatibility with observation
can be obtained for extensive new regions of the parameter space, due to
flavour-dependent effects. On the other hand, focusing on (normal) hierarchical
light and heavy neutrinos, the hypothesis that there is no CP violation
associated with the right-handed neutrino sector, and that leptogenesis
exclusively arises from the CP-violating phases of the matrix,
is only marginally consistent. Taking into account stricter bounds on
further suggests that (additional) sources of CP violation must
arise from the right-handed neutrino sector, further implying stronger
constraints for the right-handed neutrino parameters.Comment: 42 pages, 12 figures; final version published in JCAP; numerical
results for the efficiency factor can be downloaded from
http://www.newphysics.eu/leptogenesis
Extending a mobile device with low-cost 3D modeling and building-scale mapping capabilities, for application in architecture and archaeology
One of the most challenging problem in architecture is the automated construction of 3D (and 4D) digital models of cultural objects with the aim of implementing open data repositories, scientifically authenticated and responding to well accepted standards of validation, evaluation, preservation, publication, updating and dissemination. The realization of such an ambitious objective requires the adoption of special technological instruments. In this paper we plan to use portable devices (i.e. smartphones, tablets or PDAs eventually extended to wearable ones), extended with a small plug-in, for automatically extracting 3D models of single objects and building-scale mapping of the surrounding environment. At the same time, the device will provide the capability of inserting notes and observations. Where the instrument cannot be directly applied, for example for exploring the top of a complex building, we consider mounting our device, or using equivalent existing equipment, on a drone, in a modular approach for obtaining data de-facto interchangeable. The approach based on the expansion packs has the advantage of anticipating (or even promoting) future extensions of new mobile devices, when the spectrum of possible applications justify the corresponding increased costs. In order to experiment and verify this approach we plan to test it in two specific scenarios of the cultural heritage domain in which such devices seem particularly promising: Strada Nuova in Genoa and Palazzo Ducale in Urbino, both located in Italy
- …