40 research outputs found
Microscopic Calculation of the System
We report on a consistent, microscopic calculation of the bound and
scattering states in the 4He system employing a realistic nucleon-nucleon
potential in the framework of the resonating group model (RGM). We present for
comparison with these microscopic RGM calculations the results from a
charge-independent, Coulomb-corrected R-matrix analysis of all types of data
for reactions in the A=4 system. Comparisons are made between the phase shifts,
and with a selection of measurements from each reaction, as well as between the
resonance spectra obtained from both calculations. In general, the comparisons
are favorable, but distinct differences are observed between the RGM
calculations and some of the polarisation data. The partial-wave decomposition
of the experimental data produced by the R-matrix analysis shows that these
differences can be attributed to just a few S-matrix elements, for which
inadequate tensor-force strength in the N-N interaction used appears to be
responsible.Comment: 53 pages, PS document can also be found at
ftp://theorie3.physik.uni-erlangen.de/pub/publications/he4.ps.g
Equivalence classes and local asymptotic normality in system identification for quantum Markov chains
We consider the problem of identifying and estimating dynamical parameters of an ergodic quantum Markov chain, when only the stationary output is accessible for measurements. The starting point of the analysis is the fact that the knowledge of the output state completely fixes the dynamics up to an equivalence class of ‘coordinate transformation’ consisting of a multiplication by a phase and a unitary conjugation of the Kraus operators.
Assuming that the dynamics depends on an unknown parameter, we show that the latter can be estimated at the ‘standard’ rate n−1/2, and give an explicit expression of the (asymptotic) quantum Fisher information of the output, which is proportional to the Markov variance of a certain ‘generator’. More generally, we show that the output is locally asymptotically normal, i.e., it can be approximated by a simple quantum Gaussian model consisting of a coherent state whose mean is related to the unknown parameter. As a consistency check, we prove that a parameter related to the ‘coordinate transformation’ unitaries has zero quantum Fisher information
Curatela del volume: Mito e fede. Studi in onore di Giorgio Penzo / Mythos und Glaube. Festschrift fuer Giorgio Penzo
The description and analysis of system stability and change: Multi-level concepts and methodology
Policy feedback and self-reinforcing and self-undermining processes in EU biofuels policy
Evaluation of a Rotary Instrumentation Method for C-shaped Canals with Micro-computed Tomography
This study aimed to evaluate the safety and efficacy of a method of using nickel-titanium rotary instruments for preparing the C-shaped root canal system. Forty-three human mandibular second molars with a C-shaped canal configuration were prepared with a crown-down approach to an apical dimension of size 30 by using a combination of ProFile and HERO instruments. Micro-computed tomography was used to examine the canal diameter and the remaining thickness of the dentin wall along the root canal. Results showed that only isolated regions in cross section of the C-shaped canal were physically prepared by the rotary instruments. The furcal wall (concave aspect of the "C" in cross section) of all clinically identifiable canals had a similar thickness at a distance 1-7 mm from the apical constriction both before and after instrumentation. More dentin was removed from the outer (convex aspect of the "C") than the furcal aspect at the apical region, but the converse was true more coronally. All prepared canals showed a taper that matched that of the last instrument used. It was concluded that cleaning of the C-shaped canal system is incomplete with the use of rotary instruments and should be assisted by ultrasonic irrigation. Although rotary instruments seemed to be safe in such canals, further enlargement to an apical dimension greater than size 30 (0.06 taper) is not recommended. © 2008 American Association of Endodontists.link_to_subscribed_fulltex