2,287 research outputs found
Two-Frequency Jahn-Teller Systems in Circuit QED
We investigate the simulation of Jahn-Teller models with two non-degenerate
vibrational modes using a circuit QED architecture. Typical Jahn-Teller systems
are anisotropic and require at least a two-frequency description. The proposed
simulator consists of two superconducting lumped-element resonators interacting
with a common flux qubit in the ultrastrong coupling regime. We translate the
circuit QED model of the system to a two-frequency Jahn-Teller Hamiltonian and
calculate its energy eigenvalues and the emission spectrum of the cavities. It
is shown that the system can be systematically tuned to an effective single
mode Hamiltonian from the two-mode model by varying the coupling strength
between the resonators. The flexibility in manipulating the parameters of the
circuit QED simulator permits isolating the effective single frequency and pure
two-frequency effects in the spectral response of Jahn-Teller systems.Comment: 8 pages, 4 figures, figures revise
Preoperative liver registration for augmented monocular laparoscopy using backward–forward biomechanical simulation
PURPOSE: Augmented reality for monocular laparoscopy from a preoperative volume such as CT is achieved in two steps. The first step is to segment the organ in the preoperative volume and reconstruct its 3D model. The second step is to register the preoperative 3D model to an initial intraoperative laparoscopy image. To date, there does not exist an automatic initial registration method to solve the second step for the liver in the de facto operating room conditions of monocular laparoscopy. Existing methods attempt to solve for both deformation and pose simultaneously, leading to nonconvex problems with no optimal solution algorithms. METHODS: We propose in contrast to break the problem down into two parts, solving for (i) deformation and (ii) pose. Part (i) simulates biomechanical deformations from the preoperative to the intraoperative state to predict the liver’s unknown intraoperative shape by modeling gravity, the abdominopelvic cavity’s pressure and boundary conditions. Part (ii) rigidly registers the simulated shape to the laparoscopy image using contour cues. RESULTS: Our formulation leads to a well-posed problem, contrary to existing methods. This is because it exploits strong environment priors to complement the weak laparoscopic visual cues. CONCLUSION: Quantitative results with in silico and phantom experiments and qualitative results with laparosurgery images for two patients show that our method outperforms the state-of-the-art in accuracy and registration time
High-field electron transport in doped ZnO
Current-voltage characteristics have been measured for ZnO:Ga and Zn:Sb epitaxial layers with electron densities ranging from 1.4x10(17) cm(-3) to 1.1 x 10(20) cm(-3). Two-terminal samples with coplanar electrodes demonstrate virtually ohmic behavior until thermal effects come into play. Soft damage of the samples takes place at high currents. The threshold power (per electron) for the damage is nearly inversely proportional to the electron density over a wide range of electron densities. Pulsed voltage is applied in order to minimize the thermal effects, and thus an average electric field of 150 kV cm(-1) is reached in some samples subjected to 2 ns voltage pulses. The results are treated in terms of electron drift velocity estimated from the data on current and electron density under the assumption of uniform electric field. The highest velocity of similar to 1.5 x 10(7) cm s(-1) is found at an electric field of similar to 100 kV cm(-1) for the sample with an electron density of 1.4 x 10(17) cm(-3). The nonohmic behavior due to hot-electron effects is weak, and the dependence of the electron drift velocity on the doping resembles the variation of mobility
Bargaining over a finite set of alternatives
We analyze bilateral bargaining over a finite set of alternatives. We look for “good” ordinal solutions to such problems and show that Unanimity Compromise and Rational Compromise are the only bargaining rules that satisfy a basic set of properties. We then extend our analysis to admit problems with countably infinite alternatives. We show that, on this class, no bargaining rule choosing finite subsets of alternatives can be neutral. When rephrased in the utility framework of Nash (1950), this implies that there is no ordinal bargaining rule that is finite-valued
Optimal manoeuver trajectory synthesis for autonomous space and aerial vehicles and robots
© Springer Nature Switzerland AG 2019. In this paper the problem of the synthesis of optimal manoeuver trajectories for autonomous space vehicles and robots is revisited. It is shown that it is entirely feasible to construct optimal manoeuver trajectories from considerations of only the rigid body kinematics rather than the complete dynamics of the space vehicle or robot under consideration. Such an approach lends itself to several simplifications which allow the optimal angular velocity and translational velocity profiles to be constructed, purely from considerations of the body kinematic relations. In this paper the body kinematics is formulated, in general, in terms of the quaternion representation attitude and the angular velocities are considered to be the steering inputs. The optimal inputs for a typical attitude manoeuver is synthesized by solving for the states and co-states defined by a two point boundary value problem. A typical example of a space vehicle pointing problem is considered and the optimal torque inputs for the synthesis of a reference attitude trajectory and the reference trajectories are obtained
Comparative study of the (0001) and (0001) surfaces of ZnO
The authors compare the surface and optical properties of the Zn-polar (0001) and O-polar (0001¯)surfaces of bulk ZnO samples. For optical characterization, steady-state photoluminescence using a He–Cd laser was measured at 15 and 300K. At room temperature, the (0001¯)surface demonstrates nearly double the near-band-edge emission intensity seen for the (0001) surface. Using scanning Kelvin probe microscopy, the authors have measured surface contact potentials of 0.39±0.05 and 0.50±0.05V for the (0001) and (0001¯)surfaces, respectively. The resulting small difference in band bending for these two surfaces indicates that charge transfer between the surfaces is not a dominant stabilizing mechanism. Conductive atomic force microscopy studies show enhanced reverse-bias conduction in localized regions on the (0001¯) vs (0001) surface. The differences in surface conduction and band bending between the two polar surfaces can be attributed to their chemical interactions with hydrogen and water in the ambient
Dynamical analysis of a weakly coupled nonlinear dielectric waveguide -- surface-plasmon model as a new type of Josephson Junction
We propose that a weakly-coupled nonlinear dielectric waveguide --
surface-plasmon system can be formulated as a new type of Josephson junction.
Such a system can be realized along a metal - dielectric interface where the
dielectric medium hosts a nonlinear waveguide (e.g. fiber) for soliton
propagation. We demonstrate that the system is in close analogy to the bosonic
Josephson-Junction (BJJ) of atomic condensates at very low temperatures, yet
exhibits different dynamical features. In particular, the inherently dynamic
coupling parameter between soliton and surface-plasmon generates self-trapped
oscillatory states at nonzero fractional populations with zero and time
averaged phase difference. The salient features of the dynamics are presented
in the phase space.Comment: 9 pages, 7 figure
CMDX©-based single source information system for simplified quality management and clinical research in prostate cancer
Background: Histopathological evaluation of prostatectomy specimens is crucial to decision-making and prediction of patient outcomes in prostate cancer (PCa). Topographical information regarding PCa extension and positive surgical margins (PSM) is essential for clinical routines, quality assessment, and research. However, local hospital information systems (HIS) often do not support the documentation of such information. Therefore, we investigated the feasibility of integrating a cMDX-based pathology report including topographical information into the clinical routine with the aims of obtaining data, performing analysis and generating heat maps in a timely manner, while avoiding data redundancy. Methods: We analyzed the workflow of the histopathological evaluation documentation process. We then developed a concept for a pathology report based on a cMDX data model facilitating the topographical documentation of PCa and PSM; the cMDX SSIS is implemented within the HIS of University Hospital Muenster. We then generated a heat map of PCa extension and PSM using the data. Data quality was assessed by measuring the data completeness of reports for all cases, as well as the source-to-database error. We also conducted a prospective study to compare our proposed method with recent retrospective and paper-based studies according to the time required for data analysis.
Results: We identified 30 input fields that were applied to the cMDX-based data model and the electronic report was integrated into the clinical workflow. Between 2010 and 2011, a total of 259 reports were generated with 100% data completeness and a source-to-database error of 10.3 per 10,000 fields. These reports were directly reused for data analysis, and a heat map based on the data was generated. PCa was mostly localized in the peripheral zone of the prostate. The mean relative tumor volume was 16.6%. The most PSM were localized in the apical region of the prostate. In the retrospective study, 1623 paper-based reports were transferred to cMDX reports; this process took 15 ± 2 minutes per report. In a paper-based study, the analysis data preparation required 45 ± 5 minutes per report.
Conclusions: cMDX SSIS can be integrated into the local HIS and provides clinical routine data and timely heat maps for quality assessment and research purposes.
Ultrafast carrier relaxation in GaN, In_(0.05)Ga_(0.95)N and an In_(0.05)Ga_(0.95)/In_(0.15)Ga_(0.85)N Multiple Quantum Well
Room temperature, wavelength non-degenerate ultrafast pump/probe measurements
were performed on GaN and InGaN epilayers and an InGaN multiple quantum well
structure. Carrier relaxation dynamics were investigated as a function of
excitation wavelength and intensity. Spectrally-resolved sub-picosecond
relaxation due to carrier redistribution and QW capture was found to depend
sensitively on the wavelength of pump excitation. Moreover, for pump
intensities above a threshold of 100 microJ/cm2, all samples demonstrated an
additional emission feature arising from stimulated emission (SE). SE is
evidenced as accelerated relaxation (< 10 ps) in the pump-probe data,
fundamentally altering the re-distribution of carriers. Once SE and carrier
redistribution is completed, a slower relaxation of up to 1 ns for GaN and
InGaN epilayers, and 660 ps for the MQW sample, indicates carrier recombination
through spontaneous emission.Comment: submitted to Phys. Rev.
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