4,714 research outputs found
Conquest of the ghost pyramid of the superstring
We give a new Becchi-Rouet-Stora-Tyutin operator for the superstring. It
implies a quadratic gauge-fixed action, and a new gauge-invariant action with
first-class constraints. The infinite pyramid of spinor ghosts appears in a
simple way through ghost gamma matrices.Comment: 30 pages, 1 figure, Late
Investigation of non-uniform airflow signal oscillation during high frequency chest compression
BACKGROUND: High frequency chest compression (HFCC) is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC. METHODS: The computational model, which is based on previous physiological studies and represented by an electrical circuit analogue, was used for simulation of in vivo protocol that shows the nonlinearity of the respiratory system. Besides, airflow was measured during use of HFCC. We compared the simulation results to either the measured data or the previous research, to understand and explain the observations. RESULTS AND DISCUSSION: We could observe two important phenomena during respiration pertaining to the airflow signal oscillation generated by HFCC. The amplitudes of HFCC airflow signals varied depending on spontaneous airflow signals. We used the simulation results to investigate how the nonlinearity of airway resistance, lung capacitance, and inertance of air characterized the respiratory airflow. The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals. Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system. CONCLUSION: We found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals. This is due to the nonlinearity of the respiratory system, particularly variations in airway resistance
VLA-ANGST: A high-resolution HI Survey of Nearby Dwarf Galaxies
We present the "Very Large Array survey of Advanced Camera for Surveys Nearby
Galaxy Survey Treasury galaxies (VLA-ANGST)." VLA-ANGST is a National Radio
Astronomy Observatory Large Program consisting of high spectral (0.6-2.6 km/s)
and spatial (~6") resolution observations of neutral, atomic hydrogen (HI)
emission toward 35 nearby dwarf galaxies from the ANGST survey. ANGST is a
systematic HST survey to establish a legacy of uniform multi-color photometry
of resolved stars for a volume-limited sample of nearby galaxies (D\lesssim4
Mpc). VLA-ANGST provides VLA HI observations of the sub-sample of ANGST
galaxies with recent star formation that are observable from the northern
hemisphere and that were not observed in the "The HI Nearby Galaxy Survey"
(THINGS). The overarching scientific goal of VLA-ANGST is to investigate
fundamental characteristics of the neutral interstellar medium (ISM) of dwarf
galaxies. Here we describe the VLA observations, the data reduction, and the
final VLA-ANGST data products. We present an atlas of the integrated HI maps,
the intensity-weighted velocity fields, the second moment maps as a measure for
the velocity dispersion of the HI, individual channel maps, and integrated HI
spectra for each VLA-ANGST galaxy. We closely follow the observational setup
and data reduction of THINGS to achieve comparable sensitivity and angular
resolution. A major difference, however, is the high velocity resolution of the
VLA-ANGST observations (0.65 and 1.3km/s for the majority of the galaxies). The
VLA-ANGST data products are made publicly available at:
https://science.nrao.edu/science/surveys/vla-angst. With available star
formation histories from resolved stellar populations and lower resolution
ancillary observations from the FIR to the UV, VLA-ANGST will enable detailed
studies of the relationship between the ISM and star formation in dwarf
galaxies on a ~100 pc scale.Comment: 64 figures, grouped into 32. 115 pages, accepted for publication in
the Astronomical Journa
Decoherence and Programmable Quantum Computation
An examination of the concept of using classical degrees of freedom to drive
the evolution of quantum computers is given. Specifically, when externally
generated, coherent states of the electromagnetic field are used to drive
transitions within the qubit system, a decoherence results due to the back
reaction from the qubits onto the quantum field. We derive an expression for
the decoherence rate for two cases, that of the single-qubit Walsh-Hadamard
transform, and for an implementation of the controlled-NOT gate. We examine the
impact of this decoherence mechanism on Grover's search algorithm, and on the
proposals for use of error-correcting codes in quantum computation.Comment: submitted to Phys. Rev. A 35 double-spaced pages, 2 figures, in LaTe
Pseudogap in 1d revisited
Two decades ago, Sadovskii found an exact solution of a model describing a
pseudogap in electron energy spectrum (first introduced by Lee, Rice and
Anderson). The discovery of a pseudogap in high-Tc superconductors has revived
the interest to his exact solution. I review the model with the emphasis on
physical content, point out an error in the original Sadovskii's solution and
explain which problem he actually solved. A recent incorporation of Sadovskii's
ideas into a description of "hot spots" on the Fermi surface in cuprate
superconductors (Schmalian, Pines and Stojkovic) is briefly discussed.Comment: Final version to appear in PR
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