287 research outputs found
Quantum statistics and locality
It is shown that two observers have mutually commuting observables if they
are able to prepare in each subsector of their common state space some state
exhibiting no mutual correlations. This result establishes a heretofore missing
link between statistical and locality (commensurability) properties of the
observables of spacelike separated observers in relativistic quantum physics,
envisaged four decades ago by Haag and Kastler. It is based on a discussion of
coincidence experiments and suggests a physically meaningful quantitative
measure of possible violations of Einstein causality.Comment: 3 pages, no figure
Radio Labelings of Distance Graphs
A radio -labeling of a connected graph is an assignment of non
negative integers to the vertices of such that for any two vertices and , , where is the
distance between and in . In this paper, we study radio labelings of
distance graphs, i.e., graphs with the set of integers as vertex set and
in which two distinct vertices are adjacent if and only if .Comment: 14 page
A unitary correlation operator method
The short range repulsion between nucleons is treated by a unitary
correlation operator which shifts the nucleons away from each other whenever
their uncorrelated positions are within the replusive core. By formulating the
correlation as a transformation of the relative distance between particle
pairs, general analytic expressions for the correlated wave functions and
correlated operators are given. The decomposition of correlated operators into
irreducible n-body operators is discussed. The one- and two-body-irreducible
parts are worked out explicitly and the contribution of three-body correlations
is estimated to check convergence. Ground state energies of nuclei up to mass
number A=48 are calculated with a spin-isospin-dependent potential and single
Slater determinants as uncorrelated states. They show that the deduced energy-
and mass-number-independent correlated two-body Hamiltonian reproduces all
"exact" many-body calculations surprisingly well.Comment: 43 pages, several postscript figures, uses 'epsfig.cls'. Submitted to
Nucl. Phys. A. More information available at http://www.gsi.de/~fm
The Representation of Natural Numbers in Quantum Mechanics
This paper represents one approach to making explicit some of the assumptions
and conditions implied in the widespread representation of numbers by composite
quantum systems. Any nonempty set and associated operations is a set of natural
numbers or a model of arithmetic if the set and operations satisfy the axioms
of number theory or arithmetic. This work is limited to k-ary representations
of length L and to the axioms for arithmetic modulo k^{L}. A model of the
axioms is described based on states in and operators on an abstract L fold
tensor product Hilbert space H^{arith}. Unitary maps of this space onto a
physical parameter based product space H^{phy} are then described. Each of
these maps makes states in H^{phy}, and the induced operators, a model of the
axioms. Consequences of the existence of many of these maps are discussed along
with the dependence of Grover's and Shor's Algorithms on these maps. The
importance of the main physical requirement, that the basic arithmetic
operations are efficiently implementable, is discussed. This conditions states
that there exist physically realizable Hamiltonians that can implement the
basic arithmetic operations and that the space-time and thermodynamic resources
required are polynomial in L.Comment: Much rewrite, including response to comments. To Appear in Phys. Rev.
Quantum Robots and Environments
Quantum robots and their interactions with environments of quantum systems
are described and their study justified. A quantum robot is a mobile quantum
system that includes a quantum computer and needed ancillary systems on board.
Quantum robots carry out tasks whose goals include specified changes in the
state of the environment or carrying out measurements on the environment. Each
task is a sequence of alternating computation and action phases. Computation
phase activities include determination of the action to be carried out in the
next phase and possible recording of information on neighborhood environmental
system states. Action phase activities include motion of the quantum robot and
changes of neighborhood environment system states. Models of quantum robots and
their interactions with environments are described using discrete space and
time. To each task is associated a unitary step operator T that gives the
single time step dynamics. T = T_{a}+T_{c} is a sum of action phase and
computation phase step operators. Conditions that T_{a} and T_{c} should
satisfy are given along with a description of the evolution as a sum over paths
of completed phase input and output states. A simple example of a task carrying
out a measurement on a very simple environment is analyzed. A decision tree for
the task is presented and discussed in terms of sums over phase paths. One sees
that no definite times or durations are associated with the phase steps in the
tree and that the tree describes the successive phase steps in each path in the
sum.Comment: 30 Latex pages, 3 Postscript figures, Minor mathematical corrections,
accepted for publication, Phys Rev
A Quantum Anti-Zeno Paradox
We establish an exact differential equation for the operator describing
time-dependent measurements continuous in time and obtain a series solution.
Suppose the projection operator is measured
continuously from t = 0 to T, where E is a projector leaving the initial state
unchanged and U(t) a unitary operator obeying U(0) = 1 and some smoothness
conditions in t. We prove that the probability of always finding E(t) = 1 from
t = 0 to T is unity. If , the watched kettle is sure to `boil'.Comment: 10 pages,late
Dressing the nucleon in a dispersion approach
We present a model for dressing the nucleon propagator and vertices. In the
model the use of a K-matrix approach (unitarity) and dispersion relations
(analyticity) are combined. The principal application of the model lies in
pion-nucleon scattering where we discuss effects of the dressing on the phase
shifts.Comment: 17 pages, using REVTeX, 6 figure
Biallelic Loss-of-Function Variants in BICD1 Are Associated with Peripheral Neuropathy and Hearing Loss
Hearing loss and peripheral neuropathy are two clinical entities that are genetically and phenotypically heterogeneous and sometimes co-occurring. Using exome sequencing and targeted segregation analysis, we investigated the genetic etiology of peripheral neuropathy and hearing loss in a large Ashkenazi Jewish family. Moreover, we assessed the production of the candidate protein via western blotting of lysates from fibroblasts from an affected individual and an unaffected control. Pathogenic variants in known disease genes associated with hearing loss and peripheral neuropathy were excluded. A homozygous frameshift variant in the BICD1 gene, c.1683dup (p.(Arg562Thrfs*18)), was identified in the proband and segregated with hearing loss and peripheral neuropathy in the family. The BIDC1 RNA analysis from patient fibroblasts showed a modest reduction in gene transcripts compared to the controls. In contrast, protein could not be detected in fibroblasts from a homozygous c.1683dup individual, whereas BICD1 was detected in an unaffected individual. Our findings indicate that bi-allelic loss-of-function variants in BICD1 are associated with hearing loss and peripheral neuropathy. Definitive evidence that bi-allelic loss-of-function variants in BICD1 cause peripheral neuropathy and hearing loss will require the identification of other families and individuals with similar variants with the same phenotype
Sialylation of campylobacter jejuni lipo-oligosaccharides: impact on phagocytosis and cytokine production in mice
<p>Background:
Guillain-Barré syndrome (GBS) is a post-infectious polyradiculoneuropathy, frequently associated with antecedent Campylobacter jejuni (C. jejuni) infection. The presence of sialic acid on C. jejuni lipo-oligosaccharide (LOS) is considered a risk factor for development of GBS as it crucially determines the structural homology between LOS and gangliosides, explaining the induction of cross-reactive neurotoxic antibodies. Sialylated C. jejuni are recognised by TLR4 and sialoadhesin; however, the functional implications of these interactions in vivo are unknown.</p>
<p>Methodology/Principal Findings:
In this study we investigated the effects of bacterial sialylation on phagocytosis and cytokine secretion by mouse myeloid cells in vitro and in vivo. Using fluorescently labelled GM1a/GD1a ganglioside-mimicking C. jejuni strains and corresponding (Cst-II-mutant) control strains lacking sialic acid, we show that sialylated C. jejuni was more efficiently phagocytosed in vitro by BM-MΦ, but not by BM-DC. In addition, LOS sialylation increased the production of IL-10, IL-6 and IFN-β by both BM-MΦ and BM-DC. Subsequent in vivo experiments revealed that sialylation augmented the deposition of fluorescent bacteria in splenic DC, but not macrophages. In addition, sialylation significantly amplified the production of type I interferons, which was independent of pDC.</p>
<p>Conclusions/Significance:
These results identify novel immune stimulatory effects of C. jejuni sialylation, which may be important in inducing cross-reactive humoral responses that cause GBS</p>
A collaborative-interactive model for mental health consultation: Teacher inservice education by psychiatric clinicians
Primary prevention of emotional disorders is often cited as a goal in community mental health consultation. The daily contact with children and parents by the classroom teacher can yield effective prevention, if the teacher is appropriately prepared to act as a resource, and by clinicians given an awareness of emotional difficulties in children and their parents. Though consultation is often described as facilitative of change, typically discussions of such programs emphasize technique rather than content. Presented here is a collaborative model based upon a didactic input of humanistic psychology, upon which educator and clinician draw as they become allies in pursuit of answers to questions raised in current examples from the teacher's classroom experience. Excerpts and results of the model's effectiveness are given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43964/1/10578_2005_Article_BF01433269.pd
- …