4,879 research outputs found
Non-invasive single-bunch matching and emittance monitor
On-line monitoring of beam quality for high brightness beams is only possible
using non-invasive instruments. For matching measurements, very few such
instruments are available. One candidate is a quadrupole pick-up. Therefore, a
new type of quadrupole pick-up has been developed for the 26 GeV Proton
Synchrotron (PS) at CERN, and a measurement system consisting of two such
pick-ups is now installed in this accelerator. Using the information from these
pick-ups, it is possible to determine both injection matching and emittance in
the horizontal and vertical planes, for each bunch separately. This paper
presents the measurement method and some of the results from the first year of
use, as well as comparisons with other measurement methods.Comment: 10 pages, 10 figures; added figure, minor textual additions; To be
resubmitted to Phys. Rev. ST-A
Soliton response to transient trap variations
The response of bright and dark solitons to rapid variations in an expulsive
longitudinal trap is investigated. We concentrate on the effect of transient
changes in the trap frequency in the form of temporal delta kicks and the
hyperbolic cotangent functions. Exact expressions are obtained for the soliton
profiles. This is accomplished using the fact that a suitable linear
Schrodinger stationary state solution in time can be effectively combined with
the solutions of non-linear Schrodinger equation, for obtaining solutions of
the Gross-Pitaevskii equation with time dependent scattering length in a
harmonic trap. Interestingly, there is rapid pulse amplification in certain
scenarios
Quantum Mechanics Another Way
Deformation quantization (sometimes called phase-space quantization) is a
formulation of quantum mechanics that is not usually taught to undergraduates.
It is formally quite similar to classical mechanics: ordinary functions on
phase space take the place of operators, but the functions are multiplied in an
exotic way, using the star product. Here we attempt a brief, pedagogical
discussion of deformation quantization, that is suitable for inclusion in an
undergraduate course.Comment: 14 pages, 3 figures, to be published in Eur. J. Phy
Periodic Quasi - Exactly Solvable Models
Various quasi-exact solvability conditions, involving the parameters of the
periodic associated Lam{\'e} potential, are shown to emerge naturally in the
quantum Hamilton-Jacobi approach. It is found that, the intrinsic nonlinearity
of the Riccati type quantum Hamilton-Jacobi equation is primarily responsible
for the surprisingly large number of allowed solvability conditions in the
associated Lam{\'e} case. We also study the singularity structure of the
quantum momentum function, which yields the band edge eigenvalues and
eigenfunctions.Comment: 11 pages, 5 table
Calculation of Band Edge Eigenfunctions and Eigenvalues of Periodic Potentials through the Quantum Hamilton - Jacobi Formalism
We obtain the band edge eigenfunctions and the eigenvalues of solvable
periodic potentials using the quantum Hamilton - Jacobi formalism. The
potentials studied here are the Lam{\'e} and the associated Lam{\'e} which
belong to the class of elliptic potentials. The formalism requires an
assumption about the singularity structure of the quantum momentum function
, which satisfies the Riccati type quantum Hamilton - Jacobi equation, in the complex plane. Essential
use is made of suitable conformal transformations, which leads to the
eigenvalues and the eigenfunctions corresponding to the band edges in a simple
and straightforward manner. Our study reveals interesting features about the
singularity structure of , responsible in yielding the band edge
eigenfunctions and eigenvalues.Comment: 21 pages, 5 table
Exploring the concept of pain of Australian children with and without pain: Qualitative study
© 2019 Author(s). Objective A person's concept of pain can be defined as how they understand what pain actually is, what function it serves and what biological processes are thought to underpin it. This study aimed to explore the concept of pain in children with and without persistent pain. Design In-depth, face-to-face interviews with drawing tasks were conducted with 16 children (aged 8-12 years) in New South Wales, Australia. Thematic analysis was used to analyse and synthesise the data. Setting Children with persistent pain were identified from a pain clinic waiting list in Australia, and children without pain were identified through advertising flyers and email bulletins at a university and hospital. Participants Eight children had persistent pain and eight children were pain free. Results Four themes emerged from the data: â € my pain-related knowledge', â € pain in the world around me', â € pain in me' and â € communicating my concept of pain'. A conceptual framework of the potential interactions between the themes resulting from the analysis is proposed. The concept of pain of Australian children aged 8-12 years varied depending on their knowledge, experiences and literacy levels. For example, when undertaking a drawing task, children with persistent pain tended to draw emotional elements to describe pain, whereas children who were pain free did not. Conclusions Gaining an in-depth understanding of a child's previous pain-related experiences and knowledge is important to facilitate clear and meaningful pain science education. The use of age-appropriate language, in combination with appropriate assessment and education tasks such as drawing and discussing vignettes, allowed children to communicate their individual concept of pain
Angular Forces Around Transition Metals in Biomolecules
Quantum-mechanical analysis based on an exact sum rule is used to extract an
semiclassical angle-dependent energy function for transition metal ions in
biomolecules. The angular dependence is simple but different from existing
classical potentials. Comparison of predicted energies with a
computer-generated database shows that the semiclassical energy function is
remarkably accurate, and that its angular dependence is optimal.Comment: Tex file plus 4 postscript figure
Evidence for core-hole-mediated inelastic x-ray scattering from metallic FeTe
We present a detailed analysis of resonant inelastic scattering (RIXS) from
FeTe with unprecedented energy resolution. In contrast to the sharp
peaks typically seen in insulating systems at the transition metal edge,
we observe spectra which show different characteristic features. For low energy
transfer, we experimentally observe theoretically predicted many-body effects
of resonant Raman scattering from a non-interacting gas of fermions.
Furthermore, we find that limitations to this many-body electron-only theory
are realized at high Raman shift, where an exponential lineshape reveals an
energy scale not present in these considerations. This regime, identified as
emission, requires considerations of lattice degrees of freedom to understand
the lineshape. We argue that both observations are intrinsic general features
of many-body physics of metals.Comment: 4 pages, 4 figure
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