33 research outputs found
Commissioning and clinical implementation of the first commercial independent Monte Carlo 3D dose calculation to replace CyberKnife M6™ patient-specific QA measurements
Purpose: To report on the commissioning and clinical validation of the first commercially available independent Monte Carlo (MC) three-dimensional (3D) dose calculation for CyberKnife robotic radiosurgery system® (Accuray, Sunnyvale, CA).
Methods: The independent dose calculation (IDC) by SciMoCa® (Scientific RT,
Munich, Germany) was validated based on water measurements of output factors
and dose profiles (unshielded diode, field-size dependent corrections). A set of 84
patient-specific quality assurance (QA) measurements for multi-leaf collimator (MLC)
plans, using an Octavius two-dimensional SRS1000 array (PTW, Freiburg, Germany),
was compared to results of respective calculations. Statistical process control (SPC)
was used to detect plans outside action levels.
Results: Of all output factors for the three collimator systems of the CyberKnife,
99% agreed within 2% and 81% within 1%, with a maximum deviation of 3.2% for a
5-mm fixed cone. The profiles were compared using a one-dimensional gamma evaluation with 2% dose difference and 0.5 mm distance-to-agreement (Γ(2,0.5)). The
off-centre ratios showed an average pass rate >99% (92–100%). The agreement of
the depth dose profiles depended on field size, with lowest pass rates for the smallest MLC field sizes. The average depth dose pass rate was 88% (35–99%). The IDCs
showed a Γ(2,1) pass rate of 98%. Statistical process control detected six plans outside tolerance levels in the measurements, all of which could be attributed the measurement setup. Independent dose calculations showed problems in five plans, all
due to differences in the algorithm between TPS and IDC. Based on these results
changes were made in the class solution for treatment plans.
Conclusion: The first commercially available MC 3D dose IDC was successfully
commissioned and validated for the CyberKnife and replaced all routine patientspecific QA measurements in our clinic
Entangling power and operator entanglement in qudit systems
We establish the entangling power of a unitary operator on a general
finite-dimensional bipartite quantum system with and without ancillas, and give
relations between the entangling power based on the von Neumann entropy and the
entangling power based on the linear entropy. Significantly, we demonstrate
that the entangling power of a general controlled unitary operator acting on
two equal-dimensional qudits is proportional to the corresponding operator
entanglement if linear entropy is adopted as the quantity representing the
degree of entanglement. We discuss the entangling power and operator
entanglement of three representative quantum gates on qudits: the SUM, double
SUM, and SWAP gates.Comment: 8 pages, 1 figure. Version 3: Figure was improved and the MS was a
bit shortene
A 2-Component Generalization of the Camassa-Holm Equation and Its Solutions
An explicit reciprocal transformation between a 2-component generalization of
the Camassa-Holm equation, called the 2-CH system, and the first negative flow
of the AKNS hierarchy is established, this transformation enables one to obtain
solutions of the 2-CH system from those of the first negative flow of the AKNS
hierarchy. Interesting examples of peakon and multi-kink solutions of the 2-CH
system are presented.Comment: 15 pages, 16 figures, some typos correcte
Quantum Computing in the Presence of Detected Spontaneous Emission
A new method for quantum computation in the presence of detected spontaneous
emission is proposed. The method combines strong and fast (dynamical
decoupling) pulses and a quantum error correcting code that encodes logical
qubits into only physical qubits. Universal fault-tolerant quantum
computation is shown to be possible in this scheme using Hamiltonians relevant
to a range of promising proposals for the physical implementation of quantum
computers.Comment: 7 pages, no figures. This version corrects an error in the
description of spontaneous emission in the quantum jumps picture. As a
consequence the error correcting code and some aspects of the preparation,
computation, and recovery operations have been modified. The main conclusions
of the published paper remain intact. An erratum will be published shortly in
Phys. Rev. A, detailing all the corrections required in the published paper.
The present version includes all these corrections in the body of the pape
Active Brownian Particles. From Individual to Collective Stochastic Dynamics
We review theoretical models of individual motility as well as collective
dynamics and pattern formation of active particles. We focus on simple models
of active dynamics with a particular emphasis on nonlinear and stochastic
dynamics of such self-propelled entities in the framework of statistical
mechanics. Examples of such active units in complex physico-chemical and
biological systems are chemically powered nano-rods, localized patterns in
reaction-diffusion system, motile cells or macroscopic animals. Based on the
description of individual motion of point-like active particles by stochastic
differential equations, we discuss different velocity-dependent friction
functions, the impact of various types of fluctuations and calculate
characteristic observables such as stationary velocity distributions or
diffusion coefficients. Finally, we consider not only the free and confined
individual active dynamics but also different types of interaction between
active particles. The resulting collective dynamical behavior of large
assemblies and aggregates of active units is discussed and an overview over
some recent results on spatiotemporal pattern formation in such systems is
given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte
Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
Extensive experimental data from high-energy nucleus-nucleus collisions were
recorded using the PHENIX detector at the Relativistic Heavy Ion Collider
(RHIC). The comprehensive set of measurements from the first three years of
RHIC operation includes charged particle multiplicities, transverse energy,
yield ratios and spectra of identified hadrons in a wide range of transverse
momenta (p_T), elliptic flow, two-particle correlations, non-statistical
fluctuations, and suppression of particle production at high p_T. The results
are examined with an emphasis on implications for the formation of a new state
of dense matter. We find that the state of matter created at RHIC cannot be
described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted
to Nuclear Physics A as a regular article; v3 has minor changes in response
to referee comments. Plain text data tables for the points plotted in figures
for this and previous PHENIX publications are (or will be) publicly available
at http://www.phenix.bnl.gov/papers.htm
Near-IR Atlas of S0-Sa galaxies (NIRS0S)
An atlas of Ks-band images of 206 early-type galaxies is presented, including
160 S0-S0/a galaxies, 12 ellipticals, and 33 Sa galaxies. A majority of the
Atlas galaxies belong to a magnitude-limited (mB<12.5 mag) sample of 185 NIRS0S
(Near-IR S0 galaxy Survey) galaxies. To assure that mis-classified S0s are not
omitted, 25 ellipticals from RC3 classified as S0s in the Carnegie Atlas were
included in the sample. The images are 2-3 mag deeper than 2MASS images. Both
visual and photometric classifications are made. Special attention is paid to
the classification of lenses, coded in a systematic manner. A new lens-type,
called a 'barlens', is introduced. Also, boxy/peanut/x-shaped structures are
identified in many barred galaxies, even-though the galaxies are not seen in
edge-on view, indicating that vertical thickening is not enough to explain
them. Multiple lenses appear in 25% of the Atlas galaxies, which is a challenge
to the hierarchical evolutionary picture of galaxies. Such models need to
explain how the lenses were formed and survived in multiple merger events that
galaxies may have suffered during their lifetimes. Following the early
suggestion by van den Bergh, candidates of S0c galaxies are shown, which
galaxies are expected to be former Sc-type spirals stripped out of gas.Comment: 67 pages (include 16 figures and 6 tables). Accepted to MNRAS 2011
June 1
Nonlinear waves, nonlinear optics and your communications future
SIGLEAvailable from British Library Document Supply Centre-DSC:4335.26206(97-07) / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Nonlinear waves, nonlinear optics and your communications future
SIGLEAvailable from British Library Document Supply Centre-DSC:4335.26206(97-07) / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Geometric phases, reduction and Lie-Poisson structure for the resonant three-wave interaction
SIGLEAvailable from British Library Document Supply Centre-DSC:4335.26206(98/08) / BLDSC - British Library Document Supply CentreGBUnited Kingdo