859 research outputs found
Quantum Search Algorithm for Binary Constant Weight Codes
A binary constant weight code is a type of error-correcting code with a wide
range of applications. The problem of finding a binary constant weight code has
long been studied as a combinatorial optimization problem in coding theory. In
this paper, we propose a quantum search algorithm for binary constant weight
codes. Specifically, the search problem is newly formulated as a quadratic
unconstrained binary optimization (QUBO) and Grover adaptive search (GAS) is
used for providing the quadratic speedup. Focusing on the inherent structure of
the problem, we derive an upper bound on the minimum of the objective function
value and a lower bound on the exact number of solutions. In our algebraic
analysis, it was found that this proposed algorithm is capable of reducing the
number of required qubits, thus enhancing the feasibility. Additionally, our
simulations demonstrated that it reduces the query complexities by 63% in the
classical domain and 31% in the quantum domain. The proposed approach may be
useful for other quantum search algorithms and optimization problems.Comment: 11 pages, 4 figure
X-ray Observation of Mars with Suzaku at Solar Minimun
Mars was observed in X-rays during April 3-5 2008 for 82 ksec with the
Japanese Suzaku observatory. Mars has been known to emit X-rays via the
scattering of solar X-rays and via the charge exchange between neutral atoms in
the exosphere and solar wind ions. Past theoretical studies suggest that the
exospheric neutral density may vary by a factor of up to 10 over the solar
cycle. To investigate a potential change of the exospheric charge exchange
emission, Mars was observed with Suzaku at solar minimum. Significant signals
were not detected at the position of Mars in the energy band of 0.2-5 keV. A 2
sigma upper limit of the O VII line flux in 0.5-0.65 keV was 4.3
ph cm s. Comparing this upper limit to the past Chandra and
XMM-Newton observations conducted near solar maximum, it was found that the
exospheric density at solar minimum does not exceed that near solar maximum by
more than 6-70 times.Comment: 17 pages, 7 figures, accepted for publication in PAS
On the Capacity of Generalized Quadrature Spatial Modulation
In this letter, the average mutual information (AMI) of generalized
quadrature spatial modulation (GQSM) is first derived for continuous-input
continuous-output channels. Our mathematical analysis shows that the
calculation error induced by Monte Carlo integration increases exponentially
with the signal-to-noise ratio. This nature of GQSM is resolved by deriving a
closed-form expression. The derived AMI is compared with other related SM
schemes and evaluated for different antenna activation patterns. Our results
show that an equiprobable antenna selection method slightly decreases AMI of
symbols, while the method significantly improves AMI in total.Comment: 5 pages, 5 figure
On the Systematic Errors of Cosmological-Scale Gravity Tests using Redshift Space Distortion: Non-linear Effects and the Halo Bias
Redshift space distortion (RSD) observed in galaxy redshift surveys is a
powerful tool to test gravity theories on cosmological scales, but the
systematic uncertainties must carefully be examined for future surveys with
large statistics. Here we employ various analytic models of RSD and estimate
the systematic errors on measurements of the structure growth-rate parameter,
, induced by non-linear effects and the halo bias with respect to
the dark matter distribution, by using halo catalogues from 40 realisations of
comoving Mpc cosmological N-body simulations. We
consider hypothetical redshift surveys at redshifts z=0.5, 1.35 and 2, and
different minimum halo mass thresholds in the range of --
. We find that the systematic error of
is greatly reduced to ~5 per cent level, when a recently proposed
analytical formula of RSD that takes into account the higher-order coupling
between the density and velocity fields is adopted, with a scale-dependent
parametric bias model. Dependence of the systematic error on the halo mass, the
redshift, and the maximum wavenumber used in the analysis is discussed. We also
find that the Wilson-Hilferty transformation is useful to improve the accuracy
of likelihood analysis when only a small number of modes are available in power
spectrum measurements.Comment: 10 pages, 8 figures, 1 table, accepted for publication in MNRA
Variation in the diatom community under fast ice near Syowa Station, Antarctica, during the austral summer of 1997/98
Variations in abundance and community structure of diatoms under the fast ice near Syowa Station were investigated almost daily during the austral summer of 1997/98. Two periods of high chlorophyll a concentration were observed throughout the study : from the end of December to early January and from the middle to the end of January. Size fractionation of chlorophyll a revealed that phytoplankton during the former period consisted mostly of organisms larger than 20μm and during the latter period, 10-20μm. The large diatoms, Porosira pseudodenticulata and Pseudonitzschia turgiduloides, and small diatoms, Fragilariopsis spp., were the dominant organisms in the former and latter periods, respectively. Melting of the fast ice occurred in January, indicating a possibility that small sized diatoms were released from the ice to the water column. Accumulation of small diatoms in a sediment trap followed a decrease of their abundance in the water column. These results indicate that most of the ice algae detached from the ice sank directly to the bottom during the latter half of the austral summer
Flow of a circulating tumor cell and red blood cells in microvessels
Quantifying the behavior of circulating tumor cells (CTCs) in the blood stream is of fundamental importance for understanding metastasis. Here, we investigate the flow mode and velocity of CTCs interacting with red blood cells (RBCs) in various sized microvessels. The flow of leukocytes in microvessels has been described previously; a leukocyte forms a train with RBCs in small microvessels and exhibits margination in large microvessels. Important differences in the physical properties of leukocytes and CTCs result from size. The dimensions of leukocytes are similar to those of RBCs, but CTCs are significantly larger. We investigate numerically the size effects on the flow mode and the cell velocity, and we identify similarities and differences between leukocytes and CTCs. We find that a transition from train formation to margination occurs when (R-a)/tR≈1, where R is the vessel radius, a is the cell radius, and tR is the thickness of RBCs, but that the motion of RBCs differs from the case of leukocytes. Our results also show that the velocities of CTCs and leukocytes are larger than the average blood velocity, but only CTCs move faster than RBCs for microvessels of R/a≈1.5-2.0. These findings are expected to be useful not only for understanding metastasis, but also for developing microfluidic devices.Takeishi N., Imai Y., Yamaguchi T., et al. Flow of a circulating tumor cell and red blood cells in microvessels. Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 92, 6, 063011. https://doi.org/10.1103/PhysRevE.92.063011
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