5,499 research outputs found
Bifurcation structures and transient chaos in a four-dimensional Chua model
A four-dimensional four-parameter Chua model with cubic nonlinearity is
studied applying numerical continuation and numerical solutions methods.
Regarding numerical solution methods, its dynamics is characterized on Lyapunov
and isoperiodic diagrams and regarding numerical continuation method, the
bifurcation curves are obtained. Combining both methods the bifurcation
structures of the model were obtained with the possibility to describe the {\it
shrimp}-shaped domains and their endoskeletons. We study the effect of a
parameter that controls the dimension of the system leading the model to
present transient chaos with its corresponding basin of attraction being
riddled.Comment: 9 figures, to appear in PL
Flag-Dipole Spinor Fields in ESK Gravities
We consider the Riemann-Cartan geometry as a basis for the
Einstein-Sciama-Kibble theory coupled to spinor fields: we focus on and
conformal gravities, regarding the flag-dipole spinor fields, type-(4) spinor
fields under the Lounesto classification. We study such theories in specific
cases given for instance by cosmological scenarios: we find that in such
background the Dirac equation admits solutions that are not Dirac spinor
fields, but in fact the aforementioned flag-dipoles ones. These solutions are
important from a theoretical perspective, as they evince that spinor fields are
not necessarily determined by their dynamics, but also a discussion on their
structural (algebraic) properties must be carried off. Furthermore, the
phenomenological point of view is shown to be also relevant, since for
isotropic Universes they circumvent the question whether spinor fields do
undergo the Cosmological Principle.Comment: 18 pages, improved versio
Proton-Neutron Interaction near Closed Shells
Odd-odd nuclei around double shell closures are a direct source of
information on the proton-neutron interaction between valence nucleons. We have
performed shell-model calculations for doubly odd nuclei close to Pb,
Sn and Sn using realistic effective interactions derived from
the CD-Bonn nucleon-nucleon potential. The calculated results are compared with
the available experimental data, attention being focused on particle-hole and
particle-particle multiplets. While a good agreement is obtained for all the
nuclei considered, a detailed analysis of the matrix elements of the effective
interaction shows that a stronger core-polarization contribution seems to be
needed in the particle-particle case.Comment: 8 pages, 6 figures, Proccedings of the International Conference
"Nuclear Structure and Related Topics", Dubna, Russia, September 2-6, 2003,
to be published in Yadernaia Fizika (Physics of Atomic Nuclei
A Blow-Up Criterion for Classical Solutions to the Compressible Navier-Stokes Equations
In this paper, we obtain a blow up criterion for classical solutions to the
3-D compressible Naiver-Stokes equations just in terms of the gradient of the
velocity, similar to the Beal-Kato-Majda criterion for the ideal incompressible
flow. In addition, initial vacuum is allowed in our case.Comment: 25 page
Pain interference, gambling problem severity, and psychiatric disorders among a nationally representative sample of adults
Background and aims:
A paucity of studies has examined the association between gambling and pain interference. We examined differences in the associations of gambling problem severity and psychiatric disorders among a nationally representative sample of adults with varying levels of pain interference.
Methods:
Chi-square tests and logistic regression analyses were performed on National Epidemiologic Survey on Alcohol and Related Conditions data from 41,987 adult respondents (48% men; 52% women), who were categorized according to two levels of pain interference (i.e., no or low pain interference [NLPI] or moderate or severe pain interference [MSPI]) and three levels of gambling problem severity (i.e., non-gamblers or low-frequency gamblers [NG], low-risk or at-risk gamblers [LRG], and problem or pathological gamblers [PPG]).
Results:
MSPI respondents exhibited higher rates of PPG than NLPI respondents. Categories of Axis I disorders and clusters of mood, anxiety and substance-use disorders showed similarly strong associations with problem-gambling severity in MSPI and NLPI groups. Similarly strong associations between Axis II disorders (and each cluster — A, B and C) and problem-gambling severity were also observed in MSPI and NLPI groups. Exploratory analyses suggested potentially stronger relationships between PPG and dysthymia, panic disorder, and dependent personality disorder and LRG and specific phobia in NLPI compared to MSPI respondents.
Discussion and conclusions:
While MSPI is associated with PPG, largely similar patterns of associations across pain-interference levels were observed between problem-gambling severity and Axis I and Axis II psychiatric disorders
Quality control in neurosurgery training
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42455/1/31450241.pd
Diffusion MRI in early cancer therapeutic response assessment
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136261/1/nbm3458_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136261/2/nbm3458.pd
Carbon-grain sublimation: a new top-down component of protostellar chemistry
Earth's carbon deficit has been an outstanding problem in our understanding
of the formation of our Solar System. A possible solution would be the
sublimation of carbon grains at the so-called soot line (~300 K) early in the
planet-formation process. Here, we argue that the most likely signatures of
this process are an excess of hydrocarbons and nitriles inside the soot line,
and a higher excitation temperature for these molecules compared to
oxygen-bearing complex organics that desorb around the water snowline (~100 K).
Such characteristics have been reported in the literature, for example, in
Orion KL, although not uniformly, potentially due to differences in
observational settings and analysis methods of different studies or related to
the episodic nature of protostellar accretion. If this process is active, this
would mean that there is a heretofore unknown component to the carbon chemistry
during the protostellar phase that is acting from the top down - starting from
the destruction of larger species - instead of from the bottom up from atoms.
In the presence of such a top-down component, the origin of organic molecules
needs to be re-explored.Comment: Accepted for publication in ApJL. 14 pages, 2 figures, 1 table (4
pages
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