1,270 research outputs found
Origin of the Different Architectures of the Jovian and Saturnian Satellite Systems
The Jovian regular satellite system mainly consists of four Galilean
satellites that have similar masses and are trapped in mutual mean motion
resonances except for the outer satellite, Callisto. On the other hand, the
Saturnian regular satellite system has only one big icy body, Titan, and a
population of much smaller icy moons. We have investigated the origin of these
major differences between the Jovian and Saturnian satellite systems by
semi-analytically simulating the growth and orbital migration of
proto-satellites in an accreting proto-satellite disk. We set up two different
disk evolution/structure models that correspond to Jovian and Saturnian
systems, by building upon previously developed models of an actively-supplied
proto-satellite disk, the formation of gas giants, and observations of young
stars. Our simulations extend previous models by including the (1) different
termination timescales of gas infall onto the proto-satellite disk and (2)
different evolution of a cavity in the disk, between the Jovian and Saturnian
systems. We have performed Monte Carlo simulations and show that in the case of
the Jovian systems, four to five similar-mass satellites are likely to remain
trapped in mean motion resonances. This orbital configuration is formed by type
I migration, temporal stopping of the migration near the disk inner edge, and
quick truncation of gas infall caused by Jupiter opening a gap in the Solar
nebula. The Saturnian systems tend to end up with one dominant body in the
outer regions caused by the slower decay of gas infall associated with global
depletion of the Solar nebula. The total mass and compositional zoning of the
predicted Jovian and Saturnian satellite systems are consistent with the
observed satellite systems.Comment: Accepted to ApJ, 33pages, 6figures, 2table
Delusion of Oral Parasitosis and Thalamic Pain Syndrome
The official published article is available online at http://psy.psychiatryonline.org/cgi/content/abstract/50/5/534Background: Delusional parasitosis is an uncommon psychiatric condition in which patients have the immutable conviction that small, living organisms, such as worms, insects, or larvae infest their skin or other organs. Objective/Method: The authors describe a case of an unusual association of delusional parasitosis and thalamic pain syndrome after left-posterior thalamic hemorrhage. The patient initially suffered from dysesthesia and burning pain typical of thalamic pain syndrome and subsequently developed delusional oral parasitosis ("worms" infesting her mouth). Results: Sulpiride 100 mg/day administered in addition to amitriptyline gradually improved her delusions within 3 months. Discussion: The authors speculate that this specific type of delusion can be elicited by the disruption of the somatosensory pathway and that the subsequent cortical sensory deafferentiation and reorganization arising from this disruption may contribute to the development of delusional parasitosis.PSYCHOSOMATICS. 50(5):534-537 (2009)journal articl
Toward a Deterministic Model of Planetary Formation VI: Dynamical Interaction and Coagulation of Multiple Rocky Embryos and Super-Earth Systems around Solar Type Stars
Radial velocity and transit surveys indicate that solar-type stars bear
super-Earths, with mass and period up to ~ 20 M_E and a few months, are more
common than those with Jupiter-mass gas giants. In many cases, these
super-Earths are members of multiple-planet systems in which their mutual
dynamical interaction has influenced their formation and evolution. In this
paper, we modify an existing numerical population synthesis scheme to take into
account protoplanetary embryos' interaction with their evolving natal gaseous
disk, as well as their close scatterings and resonant interaction with each
other. We show that it is possible for a group of compact embryos to emerge
interior to the ice line, grow, migrate, and congregate into closely-packed
convoys which stall in the proximity of their host stars. After the disk-gas
depletion, they undergo orbit crossing, close scattering, and giant impacts to
form multiple rocky Earths or super-Earths in non-resonant orbits around ~
0.1AU with moderate eccentricities of ~0.01-0.1. We suggest that most
refractory super-Earths with period in the range of a few days to weeks may
have formed through this process. These super-Earths differ from Neptune-like
ice giants by their compact sizes and lack of a substantial gaseous envelope.Comment: 37 pages, 10 figures, accepted for publication in Ap
Three-dimensional geometric morphometrics of thorax-pelvis covariation and its potential for predicting the thorax morphology: A case study on Kebara 2 Neandertal
The skeletal torso is a complex structure of outstanding importance in understanding human body shape evolution, but reconstruction usually entails an element of subjectivity as researchers apply their own anatomical expertise to the process. Among different fossil reconstruction methods, 3D geometric morphometric techniques have been increasingly used in the last decades. Two-block partial least squares analysis has shown great potential for predicting missing elements by exploiting the covariation between two structures (blocks) in a reference sample: one block can be predicted from the other one based on the strength of covariation between blocks. The first aim of this study is to test whether this predictive approach can be used for predicting thorax morphologies from pelvis morphologies within adult Homo sapiens reference samples with known covariation between the thorax and the pelvis. The second aim is to apply this method to Kebara 2 Neandertal (Israel, ∼60 ka) to predict its thorax morphology using two different pelvis reconstructions as predictors. We measured 134 true landmarks, 720 curve semilandmarks, and 160 surface semilandmarks on 60 3D virtual torso models segmented from CT scans. We conducted three two-block partial least squares analyses between the thorax (block 1) and the pelvis (block 2) based on the H. sapiens reference samples after performing generalized Procrustes superimposition on each block separately. Comparisons of these predictions in full shape space by means of Procrustes distances show that the male-only predictive model yields the most reliable predictions within modern humans. In addition, Kebara 2 thorax predictions based on this model concur with the thorax morphology proposed for Neandertals. The method presented here does not aim to replace other techniques, but to rather complement them through quantitative prediction of a virtual 'scaffold' to articulate the thoracic fossil elements, thus extending the potential of missing data estimation beyond the methods proposed in previous works
Assessment of cervical myelopathy using transcranial magnetic stimulation and prediction of prognosis after laminoplasty
This is a non-final version of an article published in final form in SPINE 33(1): E15-E20, 2008.http://www.spinejournal.com/pt/re/spine/home | http://www.spinejournal.com/pt/re/spine/homeArticleSPINE. 33(1): E15-E20 (2008)journal articl
Characteristics of L3 nerve root radiculopathy
ArticleSURGICAL NEUROLOGY. 72(1):36-40 2009journal articl
Assessing thoraco‐pelvic covariation in Homo sapiens and Pan troglodytes: A 3D geometric morphometric approach
Objectives
Understanding thoraco‐pelvic integration in Homo sapiens and their closest living relatives (genus Pan) is of great importance within the context of human body shape evolution. However, studies assessing thoraco‐pelvic covariation across Hominoidea species are scarce, although recent research would suggest shared covariation patterns in humans and chimpanzees but also species‐specific features, with sexual dimorphism and allometry influencing thoraco‐pelvic covariation in these taxa differently.
Material and Methods
N = 30 adult H. sapiens and N = 10 adult Pan troglodytes torso 3D models were analyzed using 3D geometric morphometrics and linear measurements. Effects of sexual dimorphism and allometry on thoraco‐pelvic covariation were assessed via regression analyses, and patterns of thoraco‐pelvic covariation in humans and chimpanzees were computed via Two‐Block Partial Least Squares analyses.
Results
Results confirm the existence of common aspects of thoraco‐pelvic covariation in humans and chimpanzees, and also species‐specific covariation in H. sapiens that is strongly influenced by sexual dimorphism and allometry. Species‐specific covariation patterns in chimpanzees could not be confirmed because of the small sample size, but metrics point to a correspondence between the most caudal ribs and iliac crest morphology that would be irrespective of sex.
Conclusions
This study suggests that humans and chimpanzees share common aspects of thoraco‐pelvic covariation but might differ in others. In humans, torso integration is strongly influenced by sexual dimorphism and allometry, whilst in chimpanzees it may not be. This study also highlights the importance not only of torso widths but also of torso depths when describing patterns of thoraco‐pelvic covariation in primates. Larger samples are necessary to support these interpretations
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