37,172 research outputs found
Drag coefficients for partially inflated flat circular parachutes
Free-body tests of flat circular parachutes and determination of aerodynamic drag coefficients during partial inflatio
A "Starless" Core that Isn't: Detection of a Source in the L1014 Dense Core with the Spitzer Space Telescope
We present observations of L1014, a dense core in the Cygnus region previously thought to be starless, but data from the Spitzer Space Telescope show the presence of an embedded source. We propose a model for this source that includes a cold core, heated by the interstellar radiation field, and a low-luminosity internal source. The low luminosity of the internal source suggests a substellar object. If L1014 is representative, other "starless" cores may turn out to harbor central sources
Attitude Accessiblity as a Determinant of Object Construal and Evaluation
Attitude accessibility, the ease with which a given attitude comes to mind, has been demonstrated to affect attention. The current experiments focus on the construal of multiply-categorizable objects. They seek to provide evidence that (a) construals toward which individuals have more accessible attitudes, i.e., those that are more attitude-evoking, are more likely to influence the evaluation of related objects and that (b) this effect of attitude accessibility on construal processes can be extended to a whole series of objects which vary along multiple dimensions. Experiment 1 provides evidence that construals whose related attitudes were made more accessible via attitude rehearsal were more likely to influence the evaluation of a related target. Experiments 2 and 3 extend these findings to the domain of foods, which vary along two potential construal continua (healthiness versus tastiness), and demonstrate that if participant attitudes toward fitness are made more accessible, participants’ judgments about eating a variety of specific foods are guided more by the healthiness of the foods
Mean shear flows generated by nonlinear resonant Alfven waves
In the context of resonant absorption, nonlinearity has two different
manifestations. The first is the reduction in amplitude of perturbations around
the resonant point (wave energy absorption). The second is the generation of
mean shear flows outside the dissipative layer surrounding the resonant point.
Ruderman et al. [Phys. Plasmas 4, 75 (1997)] studied both these effects at the
slow resonance in isotropic plasmas. Clack et al. [Astron. Astrophys. 494}, 317
(2009)] investigated nonlinearity at the Alfven resonance, however, they did
not include the generation of mean shear flow. In this present paper, we
investigate the mean shear flow, analytically, and study its properties. We
find that the flow generated is parallel to the magnetic surfaces and has a
characteristic velocity proportional to , where is
the dimensionless amplitude of perturbations far away from the resonance. This
is, qualitatively, similar to the flow generated at the slow resonance. The
jumps in the derivatives of the parallel and perpendicular components of mean
shear flow across the dissipative layer are derived. We estimate the generated
mean shear flow to be of the order of in both the solar
upper chromosphere and solar corona, however, this value strongly depends on
the choice of boundary conditions. It is proposed that the generated mean shear
flow can produce a Kelvin--Helmholtz instability at the dissipative layer which
can create turbulent motions. This instability would be an additional effect,
as a Kelvin--Helmholtz instability may already exist due to the velocity field
of the resonant Alfven waves. This flow can also be superimposed onto existing
large scale motions in the solar upper atmosphere.Comment: 11 page
A new 1.6-micron map of Titan’s surface
We present a new map of Titan's surface obtained in the spectral 'window' at ∼1.6 μm between strong methane absorption. This pre-Cassini view of Titan's surface was created from images obtained using adaptive optics on the W.M. Keck II telescope and is the highest resolution map yet made of Titan's surface. Numerous surface features down to the limits of the spatial resolution (∼200–300 km) are apparent. No features are easily identifiable in terms of their geologic origin, although several are likely craters
Structural origin of the anomalous temperature dependence of the local magnetic moments in the CaFeAs family of materials
We report a combination of Fe K x-ray emission spectroscopy and
-intio calculations to investigate the correlation between structural and
magnetic degrees of freedom in CaFe(AsP). The
puzzling temperature behavior of the local moment found in rare earth-doped
CaFeAs [\textit{H. Gretarsson, et al., Phys. Rev. Lett. {\bf 110},
047003 (2013)}] is also observed in CaFe(AsP). We
explain this phenomenon based on first-principles calculations with scaled
magnetic interaction. One scaling parameter is sufficient to describe
quantitatively the magnetic moments in both CaFe(AsP) () and CaLaFeAs at all
temperatures. The anomalous growth of the local moments with increasing
temperature can be understood from the observed large thermal expansion of the
-axis lattice parameter combined with strong magnetoelastic coupling. These
effects originate from the strong tendency to form As-As dimers across the Ca
layer in the CaFeAs family of materials. Our results emphasize the
dual local-itinerant character of magnetism in Fe pnictides
Critical Exponents of the Three Dimensional Random Field Ising Model
The phase transition of the three--dimensional random field Ising model with
a discrete () field distribution is investigated by extensive Monte
Carlo simulations. Values of the critical exponents for the correlation length,
specific heat, susceptibility, disconnected susceptibility and magnetization
are determined simultaneously via finite size scaling. While the exponents for
the magnetization and disconnected susceptibility are consistent with a first
order transition, the specific heat appears to saturate indicating no latent
heat. Sample to sample fluctuations of the susceptibilty are consistent with
the droplet picture for the transition.Comment: Revtex, 10 pages + 4 figures included as Latex files and 1 in
Postscrip
A New Empirical Model for the Structural Analysis of Early-type Galaxies and a Critical Review of the Nuker Model
The Nuker law was designed to match the inner few (~3-10) arcseconds of
predominantly nearby (< 30 Mpc) early-type galaxy light-profiles; it was never
intended to describe an entire profile. The Sersic model, on the other hand,
was developed to fit the entire profile; however, due to the presence of
partially depleted galaxy cores, the Sersic model cannot always describe the
very inner region. We have therefore developed a new empirical model consisting
of an inner power-law, a transition region, and an outer Sersic model to
connect the inner and outer structure of elliptical galaxies. Moreover, the
stability of the Nuker model parameters are investigated. Surprisingly, none
are found to be stable quantities; all are shown to vary systematically with a
profile's fitted radial extent, and often by more than 100%. Considering
elliptical galaxies spanning a range of 7.5 magnitudes, the central stellar
density of the underlying host galaxy is observed to increase with galaxy
luminosity until the onset of core formation, detected only in the brightest
elliptical galaxies. We suggest that the so-called ``power-law'' galaxies may
actually be described by the Sersic model over their entire radial range
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