5,922 research outputs found
Are the Kepler Near-Resonance Planet Pairs due to Tidal Dissipation?
The multiple-planet systems discovered by the Kepler mission show an excess
of planet pairs with period ratios just wide of exact commensurability for
first-order resonances like 2:1 and 3:2. In principle, these planet pairs could
have both resonance angles associated with the resonance librating if the
orbital eccentricities are sufficiently small, because the width of first-order
resonances diverges in the limit of vanishingly small eccentricity. We consider
a widely-held scenario in which pairs of planets were captured into first-order
resonances by migration due to planet-disk interactions, and subsequently
became detached from the resonances, due to tidal dissipation in the planets.
In the context of this scenario, we find a constraint on the ratio of the
planet's tidal dissipation function and Love number that implies that some of
the Kepler planets are likely solid. However, tides are not strong enough to
move many of the planet pairs to the observed separations, suggesting that
additional dissipative processes are at play.Comment: 20 pages, including 7 figures; accepted for publication in Ap
Defect Modes in One-Dimensional Granular Crystals
We study the vibrational spectra of one-dimensional statically compressed
granular crystals (arrays of elastic particles in contact) containing defects.
We focus on the prototypical settings of one or two spherical defects
(particles of smaller radii) interspersed in a chain of larger uniform
spherical particles. We measure the near-linear frequency spectrum within the
spatial vicinity of the defects, and identify the frequencies of the localized
defect modes. We compare the experimentally determined frequencies with those
obtained by numerical eigen-analysis and by analytical expressions based on
few-site considerations. We also present a brief numerical and experimental
example of the nonlinear generalization of a single-defect localized mode
Incorporating Inertia Into Multi-Agent Systems
We consider a model that demonstrates the crucial role of inertia and
stickiness in multi-agent systems, based on the Minority Game (MG). The inertia
of an agent is introduced into the game model by allowing agents to apply
hypothesis testing when choosing their best strategies, thereby reducing their
reactivity towards changes in the environment. We find by extensive numerical
simulations that our game shows a remarkable improvement of global cooperation
throughout the whole phase space. In other words, the maladaptation behavior
due to over-reaction of agents is removed. These agents are also shown to be
advantageous over the standard ones, which are sometimes too sensitive to
attain a fair success rate. We also calculate analytically the minimum amount
of inertia needed to achieve the above improvement. Our calculation is
consistent with the numerical simulation results. Finally, we review some
related works in the field that show similar behaviors and compare them to our
work.Comment: extensively revised, 8 pages, 10 figures in revtex
On the 2:1 Orbital Resonance in the HD 82943 Planetary System
We present an analysis of the HD 82943 planetary system based on a radial
velocity data set that combines new measurements obtained with the Keck
telescope and the CORALIE measurements published in graphical form. We examine
simultaneously the goodness of fit and the dynamical properties of the best-fit
double-Keplerian model as a function of the poorly constrained eccentricity and
argument of periapse of the outer planet's orbit. The fit with the minimum
chi_{nu}^2 is dynamically unstable if the orbits are assumed to be coplanar.
However, the minimum is relatively shallow, and there is a wide range of fits
outside the minimum with reasonable chi_{nu}^2. For an assumed coplanar
inclination i = 30 deg. (sin i = 0.5), only good fits with both of the lowest
order, eccentricity-type mean-motion resonance variables at the 2:1
commensurability, theta_1 and theta_2, librating about 0 deg. are stable. For
sin i = 1, there are also some good fits with only theta_1 (involving the inner
planet's periapse longitude) librating that are stable for at least 10^8 years.
The libration semiamplitudes are about 6 deg. for theta_1 and 10 deg. for
theta_2 for the stable good fit with the smallest libration amplitudes of both
theta_1 and theta_2. We do not find any good fits that are non-resonant and
stable. Thus the two planets in the HD 82943 system are almost certainly in 2:1
mean-motion resonance, with at least theta_1 librating, and the observations
may even be consistent with small-amplitude librations of both theta_1 and
theta_2.Comment: 24 pages, including 10 figures; accepted for publication in Ap
A Processor Core Model for Quantum Computing
We describe an architecture based on a processing 'core' where multiple
qubits interact perpetually, and a separate 'store' where qubits exist in
isolation. Computation consists of single qubit operations, swaps between the
store and the core, and free evolution of the core. This enables computation
using physical systems where the entangling interactions are 'always on'.
Alternatively, for switchable systems our model constitutes a prescription for
optimizing many-qubit gates. We discuss implementations of the quantum Fourier
transform, Hamiltonian simulation, and quantum error correction.Comment: 5 pages, 2 figures; improved some arguments as suggested by a refere
Inherent Mach-Zehnder interference with "which-way" detection for single particle scattering in one dimension
We study the coherent transport of single photon in a one-dimensional
coupled-resonator-array, "non-locally" coupled to a two-level system. Since its
inherent structure is a Mach-Zehnder interferometer, we explain the destructive
interference phenomenon of the transmission spectrums according to the effect
of which-way detection. The quantum realization of the present model is a
nano-electromechanical resonator arrays with two nearest resonators coupled to
a single spin via their attached magnetic tips. Its classical simulation is a
waveguide of coupled defected cavity array with double couplings to a side
defected cavity.Comment: 5 papges, 4 figure
Multiplpe Choice Minority Game With Different Publicly Known Histories
In the standard Minority Game, players use historical minority choices as the
sole public information to pick one out of the two alternatives. However,
publishing historical minority choices is not the only way to present global
system information to players when more than two alternatives are available.
Thus, it is instructive to study the dynamics and cooperative behaviors of this
extended game as a function of the global information provided. We numerically
find that although the system dynamics depends on the kind of public
information given to the players, the degree of cooperation follows the same
trend as that of the standard Minority Game. We also explain most of our
findings by the crowd-anticrowd theory.Comment: Extensively revised, to appear in New J Phys, 7 pages with 4 figure
LIGHT AND ELECTRON MICROSCOPIC RADIOAUTOGRAPHY OF HEPATIC CELL NUCLEOLI IN MICE TREATED WITH ACTINOMYCIN D
Nucleolar partition induced by actinomycin D was used to demonstrate some aspects of nucleolar RNA synthesis and release in mouse hepatic cells, with light and electron microscopic radioautography. The effect of the drug on RNA synthesis and nucleolar morphology was studied when actinomycin D treatment preceded labeling with tritiated orotic acid. Nucleolar partition, consisting of a segegration into granular and fibrillar parts was visible if a dosage of 25 µg of actinomycin D was used, but nucleolar RNA was still synthesized. After a dosage of 400 µg of actinomycin D, nucleolar RNA synthesis was completely stopped If labeling with tritiated orotic acid preceded treatment with 400 µg of actinomycin D, labeled nucleolar RNA was present 15 min after actinomycin D treatment while high resolution radioautography showed an association of silver grains with the granular component. At 30 min after actinomicyn D treatment all labeling was lost. Since labeling was associated with the granular component the progressive loss of label as a result of actinomycin D treatment indicated a release of nucleolar granules. The correlation between this release and the loss of 28S RNA from actinomycin D treated nucleoli as described in the literature is discussed
RNA SYNTHESIS IN RAT AND MOUSE HEPATIC CELLS AS STUDIED WITH LIGHT AND ELECTRON MICROSCOPE RADIOAUTOGRAPHY
An Assessment of Risk of Iodine Deficiency Among Pregnant Women in Sarawak, Malaysia
Previous findings from a state-wide Iodine Deficiency Disorders (IDD) study among pregnant women (PW) in Sarawak indicated that PW are at risk of IDD and further assessment is needed. This paper describes the methodology used in conducting this study for an assessment of risk of iodine deficiency among pregnant women in Sarawak, Malaysia. A total of 30 maternal child health care clinics (MCHCs) were selected using probability proportional to population size (PPS) sampling technique. The PW sample size was calculated based on 95% confidence interval (CI), relative precision of 5%, design effect of 2, anticipated IDD prevalence of 65.0% and non-response rate of 20%. Thus, the total sample size required was 750 (25 respondents per selected MCHC). The WHO Expanded Programme on Immunization (EPI) surveys approach was used to randomly select the first respondent and subsequent respondents were chosen until the required number of PW was met. The required data were obtained through: face-to-face interviews (socio-demographic and food frequency questionnaire), clinical assessments (thyroid size, and hyper/hypothyroidism) and biochemical analysis (urine and blood serum). A total of 677 PW responded in the study with a response rate of 90.2%. Majority of the PW were at second gravida, aged 25-29 years old and of Malay ethnicity. The methodology used in this study was based on International guidelines which may provide state's estimates. All the necessary steps were taken into consideration to ensure valid and reliable findings on current iodine status among PW
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