12,162 research outputs found
Origin of the peculiar eccentricity distribution of the inner cold Kuiper belt
Dawson and Murray-Clay (2012) pointed out that the inner part of the cold
population in the Kuiper belt (that with semi major axis a<43.5 AU) has orbital
eccentricities significantly smaller than the limit imposed by stability
constraints. Here, we confirm their result by looking at the orbital
distribution and stability properties in proper element space. We show that the
observed distribution could have been produced by the slow sweeping of the 4/7
mean motion resonance with Neptune that accompanied the end of Neptune's
migration process. The orbital distribution of the hot Kuiper belt is not
significantly affected in this process, for the reasons discussed in the main
text. Therefore, the peculiar eccentricity distribution of the inner cold
population can not be unequivocally interpreted as evidence that the cold
population formed in-situ and was only moderately excited in eccentricity; it
can simply be the signature of Neptune's radial motion, starting from a
moderately eccentric orbit. We discuss how this agrees with a scenario of giant
planet evolution following a dynamical instability and, possibly, with the
radial transport of the cold population.Comment: in press in Icaru
Evaluation and Management of Sleep Disorders in the Hand Surgery Patient.
Despite posing a significant public health threat, sleep disorders remain poorly understood and often underdiagnosed and mismanaged. Although sleep disorders are seemingly unrelated, hand surgeons should be mindful of these because numerous conditions of the upper extremity have known associations with sleep disturbances that can adversely affect patient function and satisfaction. In addition, patients with sleep disorders are at significantly higher risk for severe, even life-threatening medical comorbidities, further amplifying the role of hand surgeons in the recognition of this condition
Chimpanzee faces under the magnifying glass: emerging methods reveal cross-species similarities and individuality
Independently, we created descriptive systems to characterize chimpanzee facial behavior, responding to a common need to have an objective, standardized coding system to ask questions about primate facial behaviors. Even with slightly different systems, we arrive at similar outcomes, with convergent conclusions about chimpanzee facial mobility. This convergence is a validation of the importance of the approach, and provides support for the future use of a facial action coding system for chimpanzees,ChimpFACS. Chimpanzees share many facial behaviors with those of humans. Therefore, processes and mechanisms that explain individual differences in facial activity can be compared with the use of a standardized systems such asChimpFACSandFACS. In this chapter we describe our independent methodological approaches, comparing how we arrived at our facial coding categories. We present some Action Descriptors (ADs) from Gaspar’s initial studies, especially focusing on an ethogram of chimpanzee and bonobo facial behavior, based on studies conducted between 1997 and 2004 at three chimpanzee colonies (The Detroit Zoo; Cleveland Metroparks Zoo; and Burger’s Zoo) and two bonobo colonies (The Columbus Zoo and Aquarium; The Milwaukee County Zoo). We discuss the potential significance of arising issues, the minor qualitative species differences that were found, and the larger quantitative differences in particular facial behaviors observed between species, e.g., bonobos expressed more movements containing particular action units (Brow Lowerer, Lip Raiser, Lip Corner Puller) compared with chimpanzees. The substantial interindividual variation in facial behavior within each species was most striking. Considering individual differences and the impact of development, we highlight the flexibility in facial activity of chimpanzees. We discuss the meaning of facial behaviors in nonhuman primates, addressing specifically individual attributes of Social Attraction, facial expressivity, and the connection of facial behavior to emotion. We do not rule out the communicative function of facial behavior, in which case an individual’s properties of facial behavior are seen as influencing his or her social life, but provide strong arguments in support of the role of facial behavior in the expression of internal states
Gravitational collapse of a magnetized fermion gas with finite temperature
We examine the dynamics of a self--gravitating magnetized electron gas at
finite temperature near the collapsing singularity of a Bianchi-I spacetime.
Considering a general and appropriate and physically motivated initial
conditions, we transform Einstein--Maxwell field equations into a complete and
self--consistent dynamical system amenable for numerical work. The resulting
numerical solutions reveal the gas collapsing into both, isotropic
("point-like") and anisotropic ("cigar-like") singularities, depending on the
initial intensity of the magnetic field. We provide a thorough study of the
near collapse behavior and interplay of all relevant state and kinematic
variables: temperature, expansion scalar, shear scalar, magnetic field,
magnetization and energy density. A significant qualitative difference in the
behavior of the gas emerges in the temperature range and .Comment: 9 pages, 7 figures. arXiv admin note: substantial text overlap with
arXiv:1211.598
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