7,380 research outputs found
Detection of a Third Planet in the HD 74156 System Using the Hobby-Eberly Telescope
We report the discovery of a third planetary mass companion to the G0 star HD
74156. High precision radial velocity measurements made with the Hobby-Eberly
Telescope aided the detection of this object. The best fit triple Keplerian
model to all the available velocity data yields an orbital period of 347 days
and minimum mass of 0.4 M_Jup for the new planet. We determine revised orbital
periods of 51.7 and 2477 days, and minimum masses of 1.9 and 8.0 M_Jup
respectively for the previously known planets. Preliminary calculations
indicate that the derived orbits are stable, although all three planets have
significant orbital eccentricities (e = 0.64, 0.43, and 0.25). With our
detection, HD 74156 becomes the eighth normal star known to host three or more
planets. Further study of this system's dynamical characteristics will likely
give important insight to planet formation and evolutionary processes.Comment: 24 pages, 4 tables, 6 figures. Accepted for publication in ApJ. V2
fixed table 4 page overrun. V3 added reference
Trust in the US-EU fruit and vegetable chain: Do US exporters understand EU importers?
Research on organizational and inter organizational trust has become an important field in management and marketing literature, as it is perceived as a pivotal aspect of business transactions. However, clarifications are still needed on the issue of whom we trust; is the person whom we are trading with trusted, or the organization, or just the product‐quality? Not only has this question not been answered within this field of research, neither have cultural differences have been described to any great extent. Additionally, if the perceived factors important to establish trusting relationships may or may not be the same on the buyers and the sellers side in international business transaction in food chains. The primary objective of this research study therefore is to identify how well US exporters understand the elements of trust that establish strong relationships with EU importers. The Analytical Hierarchy Process was used to evaluate the importance of different trust elements in interviews conducted with US exporters and EU importers of fruits and vegetables. Results are compared, providing both a picture of the important facets of trust, as well as whether the partners understand the perspectives of the other partner
Satellite detection of vegetative damage and alteration caused by pollutants emitted by a zinc smelter
The author has identified the following significant results. Field observations and data collected by low flying aircraft were used to verify the accuracy of maps produced from the satellite data. Although areas of vegetation as small as six acres can accurately be detected, a white pine stand that was severely damaged by sulfur dioxide could not be differentiated from a healthy white pine stand because spectral differences were not large enough. When winter data were used to eliminate interference from herbaceous and deciduous vegetation, the damage was still undetectable. The analysis was able to produce a character map that accurately delineated areas of vegetative alteration due to high zinc levels accumulating in the soil. The map depicted a distinct gradient of less damage and alteration as the distance from the smelter increased. Although the satellite data will probably not be useful for detecting small acreages of damaged vegetation, it is concluded that the data may be very useful as an inventory tool to detect and delineate large vegetative areas possessing differing spectral signatures
Anomalous diffusion for a class of systems with two conserved quantities
We introduce a class of one dimensional deterministic models of energy-volume
conserving interfaces. Numerical simulations show that these dynamics are
genuinely super-diffusive. We then modify the dynamics by adding a conservative
stochastic noise so that it becomes ergodic. System of conservation laws are
derived as hydrodynamic limits of the modified dynamics. Numerical evidence
shows these models are still super-diffusive. This is proven rigorously for
harmonic potentials
Magnetic structure of an imbalanced Fermi gas in an optical lattice
We analyze the repulsive fermionic Hubbard model on square and cubic lattices
with spin imbalance and in the presence of a parabolic confinement. We analyze
the magnetic structure as a function of the repulsive interaction strength and
polarization. In the first part of the paper we perform unrestricted
Hartree-Fock calculations for the 2D case and find that above a critical
interaction strength the system turns ferromagnetic at the edge of the
trap, in agreement with the ferromagnetic Stoner instability of a homogeneous
system away from half-filling. For we find a canted antiferromagnetic
structure in the Mott region in the center and a partially polarized
compressible edge. The antiferromagnetic order in the Mott plateau is
perpendicular to the direction of the imbalance. In this regime the same
qualitative behavior is expected for 2D and 3D systems. In the second part of
the paper we give a general discussion of magnetic structures above . We
argue that spin conservation leads to nontrivial textures, both in the
ferromagnetic polarization at the edge and for the Neel order in the Mott
plateau. We discuss differences in magnetic structures for 2D and 3D cases.Comment: 11 pages, 10 figures; Published versio
Photometry of Proxima Centauri and Barnard's Star Using HST Fine Guidance Sensor 3: A Search for Periodic Variations
We have observed Proxima Centauri and Barnard's Star with Hubble Space
Telescope Fine Guidance Sensor 3. Proxima Centauri exhibits small-amplitude,
periodic photometric variations. Once several sources of systematic photometric
error are corrected, we obtain 2 milli-magnitude internal photometric
precision. We identify two distinct behavior modes over the past four years:
higher amplitude, longer period; smaller amplitude, shorter period. Within the
errors one period (P ~ 83d) is twice the other. Barnard's Star shows very weak
evidence for periodicity on a timescale of approximately 130 days. If we
interpret these periodic phenomena as rotational modulation of star spots, we
identify three discrete spots on Proxima Cen and possibly one spot on Barnard's
Star. We find that the disturbances change significantly on time scales as
short as one rotation period.Comment: 39 pages, 17 figure
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