68,393 research outputs found
Effects of somatostatin on calcitonin and ectopic ACTH release in a patient with medullary thyroid carcinoma
Microscopic formula for transport coefficients of causal hydrodynamics
The Green-Kubo-Nakano formula should be modified in relativistic
hydrodynamics because of the problem of acausality and the breaking of sum
rules. In this work, we propose a formula to calculate the transport
coefficients of causal hydrodynamics based on the projection operator method.
As concrete examples, we derive the expressions for the diffusion coefficient,
the shear viscosity coefficient, and corresponding relaxation times.Comment: 4 pages, title was modified, final version published in Phys. Rev.
Monotone Volume Formulas for Geometric Flows
We consider a closed manifold M with a Riemannian metric g(t) evolving in
direction -2S(t) where S(t) is a symmetric two-tensor on (M,g(t)). We prove
that if S satisfies a certain tensor inequality, then one can construct a
forwards and a backwards reduced volume quantity, the former being
non-increasing, the latter being non-decreasing along the flow. In the case
where S=Ric is the Ricci curvature of M, the result corresponds to Perelman's
well-known reduced volume monotonicity for the Ricci flow. Some other examples
are given in the second section of this article, the main examples and
motivation for this work being List's extended Ricci flow system, the Ricci
flow coupled with harmonic map heat flow and the mean curvature flow in
Lorentzian manifolds with nonnegative sectional curvatures. With our approach,
we find new monotonicity formulas for these flows.Comment: v2: final version (as published
Frustration effects in magnetic molecules
By means of exact diagonalization we study the ground-state and the
low-temperature physics of the Heisenberg antiferromagnet on the cuboctahedron
and the icosidodecahedron. Both are frustrated magnetic polytopes and
correspond to the arrangement of magnetic atoms in the magnetic molecules
Cu12La8 and Mo72Fe30. The interplay of strong quantum fluctuations and
frustration influences the ground state spin correlations drastically and leads
to an interesting magnetization process at low temperatures. Furthermore the
frustration yields low-lying non-magnetic excitations resulting in an extra
low-temperature peak in the specific heat.Comment: 4 pages, 7 figure
Demonstration of subchondral bone density patterns by three-dimensional CT-osteoabsorptiometry (CT-OAM) as a non-invasive method for in vivo assessment of individual long-term stresses in joints
Kinematics of the South Atlantic rift
The South Atlantic rift basin evolved as branch of a large
Jurassic-Cretaceous intraplate rift zone between the African and South American
plates during the final breakup of western Gondwana. By quantitatively
accounting for crustal deformation in the Central and West African rift zone,
we indirectly construct the kinematic history of the pre-breakup evolution of
the conjugate West African-Brazilian margins. Our model suggests a causal link
between changes in extension direction and velocity during continental
extension and the generation of marginal structures such as the enigmatic
Pre-salt sag basin and the S\~ao Paulo High. We model an initial E-W directed
extension between South America and Africa (fixed in present-day position) at
very low extensional velocities until Upper Hauterivian times (126 Ma)
when rift activity along in the equatorial Atlantic domain started to increase
significantly. During this initial 17 Myr-long stretching episode the
Pre-salt basin width on the conjugate Brazilian and West African margins is
generated. An intermediate stage between 126.57 Ma and Base Aptian is
characterised by strain localisation, rapid lithospheric weakening in the
equatorial Atlantic domain, resulting in both progressively increasing
extensional velocities as well as a significant rotation of the extension
direction to NE-SW. Final breakup between South America and Africa occurred in
the conjugate Santos--Benguela margin segment at around 113 Ma and in the
Equatorial Atlantic domain between the Ghanaian Ridge and the Piau\'i-Cear\'a
margin at 103 Ma. We conclude that such a multi-velocity, multi-directional
rift history exerts primary control on the evolution of this conjugate passive
margins systems and can explain the first order tectonic structures along the
South Atlantic and possibly other passive margins.Comment: 46 Pages, 22 figures. Submitted to Solid Earth
(http://www.solid-earth.net). Abstract shortened due to arXiv restrictions.
New version contains revisions and amendments as per reviewers requests.
Supplementary data is available at
http://datahub.io/en/dataset/southatlanticrif
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