95 research outputs found
Analysis of fibre tip damage risk during pulsed holmium laser application under water
Breaking of optical fibre tips during medical holmium laser applications involving endoscopic irradiation in a liquid environment, such as arthroscopy, has been reported. This represents a risk of complications due to foreign body reactions induced by quartz fragments remaining at the operation site. Fibre breakage has been analysed under controlled conditions at clinically used laser energies of 20-1000 mJ. The generation of pressure transients at the collapse of laser-induced vapour bubbles is identified as the mechanism of fibre tip destruction. Fibre damage is observed only in a confining liquid envivronment. The highest fibre damage occurrence is observed for laser fluences of 70-250 J cm-25 at the bare fibre tip, at pulse durations of 200-350 Μs. The fibre damage occurrence and extent increase with the fibre diameter. Avoiding the identified dangerous fluence range or use of fibres smaller than 400Μm diameter is recommended to perform endoscopic holmium laser application with minimal fibre damage ris
P-055. Hardness of the zona pellucida at different stages of mouse embryonic development in vitro and in vivo as measured indirectly by a 1.48 μm diode laser
Geometric Phases and Multiple Degeneracies in Harmonic Resonators
In a recent experiment Lauber et al. have deformed cyclically a microwave
resonator and have measured the adiabatic normal-mode wavefunctions for each
shape along the path of deformation. The nontrivial observed cyclic phases
around a 3-fold degeneracy were accounted for by Manolopoulos and Child within
an approximate theory. However, open-path geometrical phases disagree with
experiment. By solving exactly the problem, we find unsuspected extra
degeneracies around the multiple one that account for the measured phase
changes throughout the path. It turns out that proliferation of additional
degeneracies around a multiple one is a common feature of quantum mechanics.Comment: 4 pages, 4 figures. Accepted in Phys. Rev. Let
Off-Diagonal Geometric Phases
We investigate the adiabatic evolution of a set of non-degenerate eigenstates
of a parameterized Hamiltonian. Their relative phase change can be related to
geometric measurable quantities that extend the familiar concept of Berry phase
to the evolution of more than one state. We present several physical systems
where these concepts can be applied, including an experiment on microwave
cavities for which off-diagonal phases can be determined from published data.Comment: 5 pages 2 figures - RevTeX. Revised version including geometrical
interpretatio
Vibrations and Berry Phases of Charged Buckminsterfullerene
A simple model of electron-vibron interactions in buckminsterfullerene ions
is solved semiclassically. Electronic degeneracies of C induce
dynamical Jahn-Teller distortions, which are unimodal for and
bimodal for . The quantization of motion along the Jahn-Teller
manifold leads to a symmetric-top rotator Hamiltonian. I find Molecular
Aharonov-Bohm effects where electronic Berry phases determine the vibrational
spectra, zero point fluctuations, and electrons' pair binding energies. The
latter are relevant to superconductivity in alkali-fullerenes.Comment: Latex 11 pages. IIT-00
Enhanced Electron Pairing in a Lattice of Berry Phase Molecules
We show that electron hopping in a lattice of molecules possessing a Berry
phase naturally leads to pairing. Our building block is a simple molecular site
model inspired by C, but realized in closer similarity with Na. In
the resulting model electron hopping must be accompanied by orbital operators,
whose function is to switch on and off the Berry phase as the electron number
changes. The effective hamiltonians (electron-rotor and electron-pseudospin)
obtained in this way are then shown to exhibit a strong pairing phenomenon, by
means of 1D linear chain case studies. This emerges naturally from numerical
studies of small -site rings, as well as from a BCS-like mean-field theory
formulation. The pairing may be explained as resulting from the exchange of
singlet pairs of orbital excitations, and is intimately connected with the
extra degeneracy implied by the Berry phase when the electron number is odd.
The relevance of this model to fullerides, to other molecular superconductors,
as well as to present and future experiments, is discussed.Comment: 30 pages, RevTe
Combining multiple optical trapping with microflow manipulation for the rapid bioanalytics on microparticles in a chip
Optical Holonomic Quantum Computer
In this paper the idea of holonomic quantum computation is realized within
quantum optics. In a non-linear Kerr medium the degenerate states of laser
beams are interpreted as qubits. Displacing devices, squeezing devices and
interferometers provide the classical control parameter space where the
adiabatic loops are performed. This results into logical gates acting on the
states of the combined degenerate subspaces of the lasers, producing any one
qubit rotations and interactions between any two qubits. Issues such as
universality, complexity and scalability are addressed and several steps are
taken towards the physical implementation of this model.Comment: 16 pages, 3 figures, REVTE
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