6,986 research outputs found
Binding energies of hydrogen-like impurities in a semiconductor in intense terahertz laser fields
A detailed theoretical study is presented for the influence of linearly
polarised intense terahertz (THz) laser radiation on energy states of
hydrogen-like impurities in semiconductors. The dependence of the binding
energy for 1s and 2p states on intensity and frequency of the THz radiation has
been examined.Comment: 14 pages, 4 figure
Quantum state engineering with flux-biased Josephson phase qubits by Stark-chirped rapid adiabatic passages
In this paper, the scheme of quantum computing based on Stark chirped rapid
adiabatic passage (SCRAP) technique [L. F. Wei et al., Phys. Rev. Lett. 100,
113601 (2008)] is extensively applied to implement the quantum-state
manipulations in the flux-biased Josephson phase qubits. The broken-parity
symmetries of bound states in flux-biased Josephson junctions are utilized to
conveniently generate the desirable Stark-shifts. Then, assisted by various
transition pulses universal quantum logic gates as well as arbitrary
quantum-state preparations could be implemented. Compared with the usual
PI-pulses operations widely used in the experiments, the adiabatic population
passage proposed here is insensitive the details of the applied pulses and thus
the desirable population transfers could be satisfyingly implemented. The
experimental feasibility of the proposal is also discussed.Comment: 9 pages, 4 figure
Interspecific hybridization between Mauremys reevesii and Mauremys sinensis: Evidence from morphology and DNA sequence data
Turtle hybrids have been found in some taxa, but so far, studies on interspecific hybridization between Mauremy reevesii and Mauremy sinensis have not been reported. Recently, we obtained three specimens (Hy1, Hy2, Hy3)with unusual morphological characteristics from pet trade Market, which are suspected to be hybrids rather than new species, because they were morphologies intermediate between M. reevesii and M. sinensis. In further study, we analyzed two aspects; morphological characteristics and molecular data, separately. The morphological characteristics showed that the pattern of the carapace, the plastron and neck stripes of the three specimens was between that of M. reevesii and M. sinensis (the morphological features of Hy1 and Hy2 have more resemblance with those of M. sinensis, and those of Hy3 have more resemblance with those of M. reevesii). In molecular analyses, two mitochondrial genes (12S, cytb) and two nuclear genes (RAG-1, R35) were respectively cloned from each suspected specimen. One sequence was obtained for each mitochondrial gene, while two different sequences were obtained for each nuclear gene. Phylogenetic analyses revealed that mitochondrial genes sequences from each suspected specimen clustered into the corresponding sequences of their putative female parents, while the two pairs nuclear parental alleles sequences were strongly paraphyletic, for they were included in two different genetic lineages (M. reevesii and M. sinensis). Therefore, we concluded that the three suspected specimens are hybrids (Hy1 and Hy2: M. reevesii♂ × M. sinensis♀; Hy3: M. sinensis♂ × M. reevesii♀). It is the first report that interspecies hybridization of M. reevesii and M. sinensis can cross completely.Key words: Mauremys reevesii, Mauremys sinensis, hybridization, morphology, DNA sequence
Extragalactic Point Source Search in WMAP 61 and 94 GHz Data
We report the results of an extragalactic point source search using the 61
and 94 GHz (V- and W-band) temperature maps from the Wilkinson Microwave
Anisotropy Probe (WMAP). Applying a method that cancels the ``noise'' due to
the CMB anisotropy signal, we find in the |b| > 10\degr region 31 sources in
the first-year maps and 64 sources in the three-year co-added maps, at a
level. The 1 position uncertainties are 1.6' and 1.4' each.
The increased detections and improved positional accuracy are expected from the
higher signal-to-noise ratio of WMAP three-year data. All sources detected in
the first-year maps are repeatedly detected in the three-year maps, which is a
strong proof of the consistency and reliability of this method. Among all the
detections, 21 are new, i.e. not in the WMAP three-year point source catalog.
We associate all but two of them with known objects. The two unidentified
sources are likely to be variable or extended as observations through VLA,
CARMA and ATCA all show non-detection at the nominal locations. We derive the
source count distribution at WMAP V-band by combining our verified detections
with sources from the WMAP three-year catalog. Assuming the effect of source
clustering is negligible, the contribution to the power spectrum from faint
sources below 0.75 Jy is estimated to be
sr for V-band, which implies a source correction amplitude sr.Comment: 22 pages, 10 figures, submitted to ApJ; Typo corrected in the
uncertainty of kappa in the Discussion, and a correction to the description
of the smoothing function in Methodolog
A replaceable-component method to construct single-degree-of-freedom multi-mode planar mechanisms with up to eight links
The multi-mode planar mechanisms (MMPMs) are excellent-performance reconfigurable mechanisms, which not only inherit structural characteristics of planar mechanisms but also have the multi-task, multi-working-condition application advantages of multi-mode mechanisms. However, lacking common bifurcation analysis and construction methods, their industrial application and development are seriously hindered. This paper presents a replaceable-component method to construct a set of single-degree-of-freedom (single-DOF) MMPMs based on the branch graphs of the corresponding planar mechanisms and the proposed multi-mode modules (MMMs). First, according to the established loop equations, all the kinematic information of the original planar mechanism is obtained by the branch graphs and singularity points using Maple. Then, compared to the relationship between the concepts of the branch and motion mode, the number and continuity of branches are taken as the index to identify the potential bifurcation and mode conversion ability for the corresponding planar mechanisms. Subsequently, the MMM is presented to help the planar mechanisms break the singularity positions to form the corresponding MMPMs, and the steps of constructing single-DOF MMPMs are summarized. Finally, a single-DOF Stephenson six-bar three-mode planar mechanism, a Watt six-bar three-mode planar mechanism, and an eight-bar four-mode planar mechanism are constructed for the first time, and the corresponding multi-mode motion analyses are made. The results can give the available configuration for the design of corresponding MMPMs. The proposed method will provide strong guidance for the configuration design of MMPMs.</p
The Anomalous Magnetic Moment of the Muon and Higgs-Mediated Flavor Changing Neutral Currents
In the two-Higgs doublet extension of the standard model, flavor-changing
neutral couplings arise naturally. In the lepton sector, the largest such
coupling is expected to be $\mu-\tau-\phi#. We consider the effects of this
coupling on the anomalous magnetic moment of the muon. The resulting bound on
the coupling, unlike previous bounds, is independent of the value of other
unknown couplings. It will be significantly improved by the upcoming E821
experiment at Brookhaven National Lab.Comment: 7 pages Latex, 2 figure
Model of coarsening and vortex formation in vibrated granular rods
Neicu and Kudrolli observed experimentally spontaneous formation of the
long-range orientational order and large-scale vortices in a system of vibrated
macroscopic rods. We propose a phenomenological theory of this phenomenon,
based on a coupled system of equations for local rods density and tilt. The
density evolution is described by modified Cahn-Hilliard equation, while the
tilt is described by the Ginzburg-Landau type equation. Our analysis shows
that, in accordance to the Cahn-Hilliard dynamics, the islands of the ordered
phase appear spontaneously and grow due to coarsening. The generic vortex
solutions of the Ginzburg-Landau equation for the tilt correspond to the
vortical motion of the rods around the cores which are located near the centers
of the islands.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
Cross-Correlation Detection of Point Sources in WMAP First Year Data
We apply a Cross-correlation (CC) method developed previously for detecting
gamma-ray point sources to the WMAP first year data by using the Point-Spread
Function of WMAP and obtain a full sky CC coefficient map. Analyzing this map,
we find that the CC method is a powerful tool to examine the WMAP foreground
residuals which can be further cleaned accordingly. Evident foreground signals
are found in WMAP foreground cleaned maps and Tegmark cleaned map. In this
process 101 point-sources are detected, and 26 of them are new sources besides
the originally listed WMAP 208 sources. We estimate the flux of these new
sources and verify them by another method. As a result, a revised mask file
based on the WMAP first year data is produced by including these new sources.Comment: 14 pages, 10 figures; accepted for publication by ChJA
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