7,575 research outputs found
Field Quantization, Photons and Non-Hermitean Modes
Field quantization in three dimensional unstable optical systems is treated
by expanding the vector potential in terms of non-Hermitean (Fox-Li) modes in
both the cavity and external regions. The cavity non-Hermitean modes (NHM) are
treated using the paraxial and monochromaticity approximations. The NHM
bi-orthogonality relationships are used in a standard canonical quantization
procedure based on introducing generalised coordinates and momenta for the
electromagnetic (EM) field. The quantum EM field is equivalent to a set of
quantum harmonic oscillators (QHO), associated with either the cavity or the
external region NHM. This confirms the validity of the photon model in unstable
optical systems, though the annihilation and creation operators for each QHO
are not Hermitean adjoints. The quantum Hamiltonian for the EM field is the sum
of non-commuting cavity and external region contributions, each of which is sum
of independent QHO Hamiltonians for each NHM, but the external field
Hamiltonian also includes a coupling term responsible for external NHM photon
exchange processes. Cavity energy gain and loss processes is associated with
the non-commutativity of cavity and external region operators, given in terms
of surface integrals involving cavity and external region NHM functions on the
cavity-external region boundary. The spontaneous decay of a two-level atom
inside an unstable cavity is treated using the essential states approach and
the rotating wave approximation. Atomic transitions leading to cavity NHM
photon absorption have a different coupling constant to those leading to photon
emission, a feature resulting from the use of NHM functions. Under certain
conditions the decay rate is enhanced by the Petermann factor.Comment: 38 pages, tex, 2 figures, ps. General expression for decay rate
added. To be published in Journal of Modern Optic
Neuromyelitis optica spectrum disorder in three generations of a Chinese family
© 2019 Neuromyelitis optica spectrum disorder is an inflammatory demyelinating disease that is largely sporadic. Familial disease has been reported in one or two generations, although its basis remains unknown. We report here three subjects meeting diagnostic criteria for NMOSD in one family: a father and son, and the maternal aunt of the father. Anticipation, of 27 years, was apparent in transmission from father to son. Aquaporin-4 antibodies were observed in the aunt but not the father and son, nor in other family members. A putative pathogenic mutation in the NECL2 gene was not found in this pedigree. This first report of NMOSD in three generations of one family underlines the heterogeneity of familial NMOSD
Non-Markovian Decay of a Three Level Cascade Atom in a Structured Reservoir
We present a formalism that enables the study of the non-Markovian dynamics
of a three-level ladder system in a single structured reservoir. The
three-level system is strongly coupled to a bath of reservoir modes and two
quantum excitations of the reservoir are expected. We show that the dynamics
only depends on reservoir structure functions, which are products of the mode
density with the coupling constant squared. This result may enable pseudomode
theory to treat multiple excitations of a structured reservoir. The treatment
uses Laplace transforms and an elimination of variables to obtain a formal
solution. This can be evaluated numerically (with the help of a numerical
inverse Laplace transform) and an example is given. We also compare this result
with the case where the two transitions are coupled to two separate structured
reservoirs (where the example case is also analytically solvable)
The percutaneous absorption of soman in a damaged skin porcine model and the evaluation of WoundStat™ as a topical decontaminant
PURPOSE: The aim of this study was to evaluate a candidate haemostat (WoundStat™), down-selected from previous in vitro studies, for efficacy as a potential skin decontaminant against the chemical warfare agent pinacoyl methylfluorophosphonate (Soman, GD) using an in vivo pig model. MATERIALS AND METHODS: An area of approximately 3 cm2 was dermatomed from the dorsal ear skin to a nominal depth of 100 µm. A discrete droplet of 14C-GD (300 µg kg-1) was applied directly onto the surface of the damaged skin at the centre of the dosing site. Animals assigned to the treatment group were given a 2 g application of WoundStat™ 30 s after GD challenge. The decontamination efficacy of WoundStat™ against GD was measured by the direct quantification of the distribution of 14C-GD, as well as routine determination of whole blood cholinesterase and physiological measurements. RESULTS: WoundStat™ sequestered approximately 70% of the applied 14C-GD. Internal radiolabel recovery from treated animals was approximately 1% of the initially applied dose. Whole blood cholinesterase levels decreased to less than 10% of the original value by 15 min post WoundStat™ treatment and gradually decreased until the onset of apnoea or until euthanasia. All treated animals showed signs of GD intoxication that could be grouped into early (mastication, fasciculations and tremor), intermediate (miosis, salivation and nasal secretions) and late onset (lacrimation, body spasm and apnoea) effects. Two of the six WoundStat™ treated animals survived the study duration. CONCLUSIONS: The current study has shown that the use of WoundStat™ as a decontaminant on damaged pig ear skin was unable to fully protect against GD toxicity. Importantly, the findings indicate that the use of WoundStat™ in GD contaminated wounds would not exacerbate GD toxicity. These data suggest that absorbent haemostatic products may offer some limited functionality as wound decontaminants.Peer reviewedFinal Accepted Versio
Controlled coupling of counterpropagating whispering-gallery modes by a single Rayleigh scatterer: a classical problem in a quantum optical light
We present experiments where a single subwavelength scatterer is used to
examine and control the back-scattering induced coupling between
counterpropagating high-Q modes of a microsphere resonator. Our measurements
reveal the standing wave character of the resulting symmetric and antisymmetric
eigenmodes, their unbalanced intensity distributions, and the coherent nature
of their coupling. We discuss our findings and the underlying classical physics
in the framework common to quantum optics and provide a particularly intuitive
explanation of the central processes.Comment: accepted for publication in Pysical Review Letter
Make It Too Difficult and I’ll Give-Up; Let Me Succeed and I’ll Excel: The Interaction between Assigned and Personal Goals
We examine the motivational effects of setting both assigned and personal non-binding goals on a real effort laboratory experiment. In order to derive conjectures for our experiment, we develop a model with goal-dependent preferences. In line with previous studies, we find that goal setting leads to a higher performance. We also find that goal-setting is most effective if subjects were able to achieve previous goals. Therefore, in goal setting, “success breeds success”. In particular, we observe that when subjects are initially allowed to attain assigned goals, they are better at self-motivating in the future when performing under personal goals
Discovery of the VHE gamma-ray source HESS J1641-463
A new TeV source, HESS J1641-463, has been serendipitously discovered in the
Galactic plane by the High Energy Stereoscopic System (H.E.S.S.) at a
significance level of 8.6 standard deviations. The observations of HESS
J1641-463 were performed between 2004 and 2011 and the source has a moderate
flux level of 1.7% of the Crab Nebula flux at E > 1 TeV. HESS J1641-463 has a
rather hard photon index of 1.99 +- 0.13_stat +- 0.20_sys. HESS J1641-463 is
positionally coincident with the radio supernova remnant SNR G338.5+0.1, but no
clear X-ray counterpart has been found in archival Chandra observations of the
region. Different possible VHE production scenarios will be discussed in this
contribution.Comment: 5 pages, 5 figures, 2012 Fermi Symposium proceedings - eConf C12102
Theory of Pseudomodes in Quantum Optical Processes
This paper deals with non-Markovian behaviour in atomic systems coupled to a
structured reservoir of quantum EM field modes, with particular relevance to
atoms interacting with the field in high Q cavities or photonic band gap
materials. In cases such as the former, we show that the pseudo mode theory for
single quantum reservoir excitations can be obtained by applying the Fano
diagonalisation method to a system in which the atomic transitions are coupled
to a discrete set of (cavity) quasimodes, which in turn are coupled to a
continuum set of (external) quasimodes with slowly varying coupling constants
and continuum mode density. Each pseudomode can be identified with a discrete
quasimode, which gives structure to the actual reservoir of true modes via the
expressions for the equivalent atom-true mode coupling constants. The quasimode
theory enables cases of multiple excitation of the reservoir to now be treated
via Markovian master equations for the atom-discrete quasimode system.
Applications of the theory to one, two and many discrete quasimodes are made.
For a simple photonic band gap model, where the reservoir structure is
associated with the true mode density rather than the coupling constants, the
single quantum excitation case appears to be equivalent to a case with two
discrete quasimodes
Experimental feedback control of quantum systems using weak measurements
A goal of the emerging field of quantum control is to develop methods for
quantum technologies to function robustly in the presence of noise. Central
issues are the fundamental limitations on the available information about
quantum systems and the disturbance they suffer in the process of measurement.
In the context of a simple quantum control scenario--the stabilization of
non-orthogonal states of a qubit against dephasing--we experimentally explore
the use of weak measurements in feedback control. We find that, despite the
intrinsic difficultly of implementing them, weak measurements allow us to
control the qubit better in practice than is even theoretically possible
without them. Our work shows that these more general quantum measurements can
play an important role for feedback control of quantum systems.Comment: 4 pages, 3 figures. v2 Added extra citation, journal reference and
DOI. Minor typographic correction
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