56,338 research outputs found
Discovery of a new supernova remnant G150.3+4.5
Large-scale radio continuum surveys have good potential for discovering new
Galactic supernova remnants (SNRs). Surveys of the Galactic plane are often
limited in the Galactic latitude of |b| ~ 5 degree. SNRs at high latitudes,
such as the Cygnus Loop or CTA~1, cannot be detected by surveys in such limited
latitudes. Using the available Urumqi 6 cm Galactic plane survey data, together
with the maps from the extended ongoing 6 cm medium latitude survey, we wish to
discover new SNRs in a large sky area. We searched for shell-like structures
and calculated radio spectra using the Urumqi 6 cm, Effelsberg 11 cm, and 21 cm
survey data. Radio polarized emission and evidence in other wavelengths are
also examined for the characteristics of SNRs. We discover an enclosed
oval-shaped object G150.3+4.5 in the 6 cm survey map. It is about 2.5 degree
wide and 3 degree high. Parts of the shell structures can be identified well in
the 11 cm, 21 cm, and 73.5 cm observations. The Effelsberg 21 cm total
intensity image resembles most of the structures of G150.3+4.5 seen at 6 cm,
but the loop is not closed in the northwest. High resolution images at 21 cm
and 73.5 cm from the Canadian Galactic Plane Survey confirm the extended
emission from the eastern and western shells of G150.3+4.5. We calculated the
radio continuum spectral indices of the eastern and western shells, which are
and between 6 cm and 21 cm, respectively.
The shell-like structures and their non-thermal nature strongly suggest that
G150.3+4.5 is a shell-type SNR. For other objects in the field of view,
G151.4+3.0 and G151.2+2.6, we confirm that the shell-like structure G151.4+3.0
very likely has a SNR origin, while the circular-shaped G151.2+2.6 is an HII
region with a flat radio spectrum, associated with optical filamentary
structure, H, and infrared emission.Comment: 5 pages, 3 figures, accepted for publication of Astronomy and
Astrophysic
Preparation of cluster states and W states with superconducting- quantum-interference-device qubits in cavity QED
We propose schemes to create cluster states and W states by many
superconducting-quantum-interference-device (SQUID) qubits in cavities under
the influence of the cavity decay. Our schemes do not require auxiliary qubits,
and the excited levels are only virtually coupled throughout the scheme, which
could much reduce the experimental challenge. We consider the cavity decay in
our model and analytically demonstrate its detrimental influence on the
prepared entangled states.Comment: 6 pages, 3 figures, to appear in Phys. Rev.
Universal quantum computation with electronic qubits in decoherence-free subspace
We investigate how to carry out universal quantum computation
deterministically with free electrons in decoherence-free subspace by using
polarizing beam splitters, charge detectors, and single-spin rotations. Quantum
information in our case is encoded in spin degrees of freedom of the
electron-pairs which construct a decoherence-free subspace. We design building
blocks for two noncommutable single-logic-qubit gates and a logic controlled
phase gate, based on which a universal and scalable quantum information
processing robust to dephasing is available in a deterministic way.Comment: 14 pages, 3 figure
Enumeration of Corners in Tree-like Tableaux
In this paper, we confirm conjectures of Laborde-Zubieta on the enumeration
of corners in tree-like tableaux and in symmetric tree-like tableaux. In the
process, we also enumerate corners in (type ) permutation tableaux and
(symmetric) alternative tableaux. The proof is based on Corteel and Nadeau's
bijection between permutation tableaux and permutations. It allows us to
interpret the number of corners as a statistic over permutations that is easier
to count. The type case uses the bijection of Corteel and Kim between type
permutation tableaux and signed permutations. Moreover, we give a bijection
between corners and runs of size 1 in permutations, which gives an alternative
proof of the enumeration of corners. Finally, we introduce conjectural
polynomial analogues of these enumerations, and explain the implications on the
PASEP.Comment: 26 pages, 11 figures. This is the final version for publicatio
Low frequency oscillations in total ozone measurements
Low frequency oscillations with periods of approximately one to two months are found in eight years of global grids of total ozone data from the Total Ozone Mapping Spectrometer (TOMS) satellite instrument. The low frequency oscillations corroborate earlier analyses based on four years of data. In addition, both annual and seasonal one-point correlation maps based on the 8-year TOMS data are presented. The results clearly show a standing dipole in ozone perturbations, oscillating with 35 to 50 day periods over the equatorial Indian Ocean-west Pacific region. This contrasts with the eastward moving dipole reported in other data sets. The standing ozone dipole appears to be a dynamical feature associated with vertical atmospheric motions. Consistent with prior analyses based on lower stratospheric temperature fields, large-scale standing patterns are also found in the extratropics of both hemispheres, correlated with ozone fluctuations over the equatorial west Pacific. In the Northern Hemisphere, a standing pattern is observed extending from the tropical Indian Ocean to the north Pacific, across North America, and down to the equatorial Atlantic Ocean region. This feature is most pronounced in the NH summer
Parameter estimation of GOES precipitation index at different calibration timescales
We examined two techniques that adjust the parameters of the GOES Precipitation Index (GPI) by combining the polar microwave and the geosynchronous infrared observations at three frequencies: daily, pentad, and monthly. The first technique is the adjusted GPI (AGPI), and the second is the universally adjusted GPI (UAGPI). The study shows that rainfall estimates can be improved by frequent calibrations providing there is sufficient superior (microwave) rainfall sampling within the calibration time and space domain. For this work, daily and pentad calibrations produce monthly rainfall estimates almost as good as monthly calibration. The daily calibration produced better daily rainfall estimates than pentad and monthly calibration, but it generates similar pentad rainfall estimates to these of the pentad calibration. The monthly calibrated scheme is not suitable for the daily and pentad rainfall estimates. Under the current twice-per-day sampling rate of polar-orbiting microwave observations, the pentad calibration scheme is suggested for the monthly, pentad, and daily rainfall. The potentials of applying the UAGPI and the AGPI techniques for daily rainfall estimation are also investigated. Copyright 2000 by the American Geophysical Union
- …