2,203 research outputs found
On the Mass-Period Correlation of the Extrasolar Planets
We report on a possible correlation between the masses and periods of the
extrasolar planets, manifested as a paucity of massive planets with short
orbital periods. Monte-Carlo simulations show the effect is significant, and is
not solely due to an observational selection effect. We also show the effect is
stronger than the one already implied by published models that assumed
independent power-law distributions for the masses and periods of the
extrasolar planets. Planets found in binary stellar systems may have an
opposite correlation. The difference is highly significant despite the small
number of planets in binary systems. We discuss the paucity of short-period
massive planets in terms of some theories for the close-in giant planets.
Almost all models can account for the deficit of massive planets with short
periods, in particular the model that assumes migration driven by a planet-disk
interaction, if the planet masses do not scale with their disk masses.Comment: 13 pages, 4 figures, accepted for publication in The Astrophysical
Journal Letter
Acute Malnutrition and Under-5 Mortality, Northeastern Part of India.
We assessed the prevalence of childhood acute malnutrition and under-five mortality rate (U5MR) in Darbhanga district, India, using a two-stage 49-cluster household survey. A total of 1379 households comprising 8473 people were interviewed. During a 90-day recall period, U5MR was 0.5 [95% confidence interval (CI), 0.2-1.4] per 10 000 per day. The prevalence of global acute malnutrition among 1405 children aged 6-59 months was 15.4% (NCHS) and 19.4% (2006 WHO references). This survey suggests that in Darbhanga district, the population is in a borderline food crisis with few food resources. Appropriate strategies should be developed to improve the overall nutritional and health status of children
Dynamical Stability and Habitability of Gamma Cephei Binary-Planetary System
It has been suggested that the long-lived residual radial velocity variations
observed in the precision radial velocity measurements of the primary of Gamma
Cephei (HR8974, HD222404, HIP116727) are likely due to a Jupiter-like planet
around this star (Hatzes et al, 2003). In this paper, the orbital dynamics of
this plant is studied and also the possibility of the existence of a
hypothetical Earth-like planet in the habitable zone of its central star is
discussed. Simulations, which have been carried out for different values of the
eccentricity and semimajor axis of the binary, as well as the orbital
inclination of its Jupiter-like planet, expand on previous studies of this
system and indicate that, for the values of the binary eccentricity smaller
than 0.5, and for all values of the orbital inclination of the Jupiter-like
planet ranging from 0 to 40 degrees, the orbit of this planet is stable. For
larger values of the binary eccentricity, the system becomes gradually
unstable. Integrations also indicate that, within this range of orbital
parameters, a hypothetical Earth-like planet can have a long-term stable orbit
only at distances of 0.3 to 0.8 AU from the primary star. The habitable zone of
the primary, at a range of approximately 3.1 to 3.8 AU, is, however, unstable.Comment: 25 pages, 7 figures, 3 tables, submitted for publicatio
A Role for Phosphoinositides in Regulating Plant Nuclear Functions
Nuclear localized inositol phospholipids and inositol phosphates are important for regulating many essential processes in animal and yeast cells such as DNA replication, recombination, RNA processing, mRNA export and cell cycle progression. An overview of the current literature indicates the presence of a plant nuclear phosphoinositide (PI) pathway. Inositol phospholipids, inositol phosphates, and enzymes of the PI pathway have been identified in plant nuclei and are implicated in DNA replication, chromatin remodeling, stress responses and hormone signaling. In this review, the potential functions of the nuclear PI pathway in plants are discussed within the context of the animal and yeast literature. It is anticipated that future research will help shed light on the functional significance of the nuclear PI pathway in plants
High resolution quantum sensing with shaped control pulses
We investigate the application of amplitude-shaped control pulses for
enhancing the time and frequency resolution of multipulse quantum sensing
sequences. Using the electronic spin of a single nitrogen vacancy center in
diamond and up to 10,000 coherent microwave pulses with a cosine square
envelope, we demonstrate 0.6 ps timing resolution for the interpulse delay.
This represents a refinement by over 3 orders of magnitude compared to the 2 ns
hardware sampling. We apply the method for the detection of external AC
magnetic fields and nuclear magnetic resonance signals of carbon-13 spins with
high spectral resolution. Our method is simple to implement and especially
useful for quantum applications that require fast phase gates, many control
pulses, and high fidelity.Comment: 5 pages, 4 figures, plus supplemental materia
Planets in binary systems: is the present configuration indicative of the formation process?
The present dynamical configuration of planets in binary star systems may not
reflect their formation process since the binary orbit may have changed in the
past after the planet formation process was completed. An observed binary
system may have been part of a former hierarchical triple that became unstable
after the planets completed their growth around the primary star.
Alternatively, in a dense stellar environment even a single stellar encounter
between the star pair and a singleton may singificantly alter the binary orbit.
In both cases the planets we observe at present would have formed when the
dynamical environment was different from the presently observed one.
We have numerically integrated the trajectories of the stars (binary plus
singleton) and of test planets to investigate the abovementioned mechanisms.
Our simulations show that the circumstellar environment during planetary
formation around the primary was gravitationally less perturbed when the binary
was part of a hierarchical triple because the binary was necessarely wider and,
possibly, less eccentric. This circumstance has consequences for the planetary
system in terms of orbital spacing, eccentricity, and mass of the individual
planets. Even in the case of a single stellar encounter the present appearance
of a planetary system in a binary may significantly differ from what it had
while planet formation was ongoing. However, while in the case of instability
of a triple the trend is always towards a tighter and more eccentric binary
system, when a single stellar encounter affects the system the orbit of the
binary can become wider and be circularized.Comment: 5 pages, 5 figures Accepted for publication on A&
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