22,721 research outputs found
Partnership research with older people: moving towards making the rhetoric a reality
As nursing develops closer partnerships with older people in delivering care, it also needs to develop partnerships in order to create the knowledge base for practice in a way that challenges professional hegemony and empowers older people. However, the process of developing partnerships in research takes place against a background of academic research traditions and norms, which can present obstacles to collaboration. This paper is a reflection on the issues that have arisen in three projects where older people were involved in research at different levels, from sources of data to independent researchers. It points to some of the areas that need further exploration and development
Extracting text from PostScript
We show how to extract plain text from PostScript files. A textual scan is inadequate because PostScript interpreters can generate characters on the page that do not appear in the source file. Furthermore, word and line breaks are implicit in the graphical rendition, and must be inferred from the positioning of word fragments. We present a robust technique for extracting text and recognizing words and paragraphs. The method uses a standard PostScript interpreter but redefines several PostScript operators, and simple heuristics are employed to locate word and line breaks. The scheme has been used to create a full-text index, and plain-text versions, of 40,000 technical reports (34 Gbyte of PostScript). Other text-extraction systems are reviewed: none offer the same combination of robustness and simplicity
Simplicity of extremal eigenvalues of the Klein-Gordon equation
We consider the spectral problem associated with the Klein-Gordon equation
for unbounded electric potentials. If the spectrum of this problem is contained
in two disjoint real intervals and the two inner boundary points are
eigenvalues, we show that these extremal eigenvalues are simple and possess
strictly positive eigenfunctions. Examples of electric potentials satisfying
these assumptions are given
Temporal Ordering in Quantum Mechanics
We examine the measurability of the temporal ordering of two events, as well
as event coincidences. In classical mechanics, a measurement of the
order-of-arrival of two particles is shown to be equivalent to a measurement
involving only one particle (in higher dimensions). In quantum mechanics, we
find that diffraction effects introduce a minimum inaccuracy to which the
temporal order-of-arrival can be determined unambiguously. The minimum
inaccuracy of the measurement is given by dt=1/E where E is the total kinetic
energy of the two particles. Similar restrictions apply to the case of
coincidence measurements. We show that these limitations are much weaker than
limitations on measuring the time-of-arrival of a particle to a fixed location.Comment: New section added, arguing that order-of-arrival can be measured more
accurately than time-of-arrival. To appear in Journal of Physics
Long-Time Dynamics of Variable Coefficient mKdV Solitary Waves
We study the Korteweg-de Vries-type equation dt u=-dx(dx^2 u+f(u)-B(t,x)u),
where B is a small and bounded, slowly varying function and f is a
nonlinearity. Many variable coefficient KdV-type equations can be rescaled into
this equation. We study the long time behaviour of solutions with initial
conditions close to a stable, B=0 solitary wave. We prove that for long time
intervals, such solutions have the form of the solitary wave, whose centre and
scale evolve according to a certain dynamical law involving the function
B(t,x), plus an H^1-small fluctuation.Comment: 19 page
Dipoles in Graphene Have Infinitely Many Bound States
We show that in graphene charge distributions with non-vanishing dipole
moment have infinitely many bound states. The corresponding eigenvalues
accumulate at the edges of the gap faster than any power
Adiabatically switched-on electrical bias in continuous systems, and the Landauer-Buttiker formula
Consider a three dimensional system which looks like a cross-connected pipe
system, i.e. a small sample coupled to a finite number of leads. We investigate
the current running through this system, in the linear response regime, when we
adiabatically turn on an electrical bias between leads. The main technical tool
is the use of a finite volume regularization, which allows us to define the
current coming out of a lead as the time derivative of its charge. We finally
prove that in virtually all physically interesting situations, the conductivity
tensor is given by a Landauer-B{\"u}ttiker type formula.Comment: 20 pages, submitte
Bound States at Threshold resulting from Coulomb Repulsion
The eigenvalue absorption for a many-particle Hamiltonian depending on a
parameter is analyzed in the framework of non-relativistic quantum mechanics.
The long-range part of pair potentials is assumed to be pure Coulomb and no
restriction on the particle statistics is imposed. It is proved that if the
lowest dissociation threshold corresponds to the decay into two likewise
non-zero charged clusters then the bound state, which approaches the threshold,
does not spread and eventually becomes the bound state at threshold. The
obtained results have applications in atomic and nuclear physics. In
particular, we prove that atomic ion with atomic critical charge and
electrons has a bound state at threshold given that , whereby the electrons are treated as fermions and the mass of the
nucleus is finite.Comment: This is a combined and updated version of the manuscripts
arXiv:math-ph/0611075v2 and arXiv:math-ph/0610058v
Alternative linear structures for classical and quantum systems
The possibility of deforming the (associative or Lie) product to obtain
alternative descriptions for a given classical or quantum system has been
considered in many papers. Here we discuss the possibility of obtaining some
novel alternative descriptions by changing the linear structure instead. In
particular we show how it is possible to construct alternative linear
structures on the tangent bundle TQ of some classical configuration space Q
that can be considered as "adapted" to the given dynamical system. This fact
opens the possibility to use the Weyl scheme to quantize the system in
different non equivalent ways, "evading", so to speak, the von Neumann
uniqueness theorem.Comment: 32 pages, two figures, to be published in IJMP
Generalized MICZ-Kepler Problems and Unitary Highest Weight Modules
For each integer , we demonstrate that a -dimensional
generalized MICZ-Kepler problem has an \mr{Spin}(2, 2n+2) dynamical symmetry
which extends the manifest \mr{Spin}(2n+1) symmetry. The Hilbert space of
bound states is shown to form a unitary highest weight \mr{Spin}(2,
2n+2)-module which occurs at the first reduction point in the
Enright-Howe-Wallach classification diagram for the unitary highest weight
modules. As a byproduct, we get a simple geometric realization for such a
unitary highest weight \mr{Spin}(2, 2n+2)-module.Comment: 27 pages, Refs. update
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