5,622 research outputs found
"Hazardous zones" within "security perimeter": comparative study on the material of folkloric discourse
The article considers the concept of "house" as a core element of "security perimeter" (the term by A. Leroy-Gourhan) on the material of English, Russian and Scottish ballad
Surface mixing and biological activity in the four Eastern Boundary Upwelling Systems
Eastern Boundary Upwelling Systems (EBUS) are characterized by a high
productivity of plankton associated with large commercial fisheries, thus
playing key biological and socio-economical roles. The aim of this work is to
make a comparative study of these four upwelling systems focussing on their
surface stirring, using the Finite Size Lyapunov Exponents (FSLEs), and their
biological activity, based on satellite data. First, the spatial distribution
of horizontal mixing is analysed from time averages and from probability
density functions of FSLEs. Then we studied the temporal variability of surface
stirring focussing on the annual and seasonal cycle. There is a global negative
correlation between surface horizontal mixing and chlorophyll standing stocks
over the four areas. To try to better understand this inverse relationship, we
consider the vertical dimension by looking at the Ekman-transport and vertical
velocities. We suggest the possibility of a changing response of the
phytoplankton to sub/mesoscale turbulence, from a negative effect in the very
productive coastal areas to a positive one in the open ocean.Comment: 12 pages. NPG Special Issue on "Nonlinear processes in oceanic and
atmospheric flows". Open Access paper, available also at the publisher site:
http://www.nonlin-processes-geophys.net/16/557/2009
Baryon Electromagnetic Properties in Partially Quenched Heavy Hadron Chiral Perturbation Theory
The electromagnetic properties of baryons containing a heavy quark are
calculated at next-to-leading order in partially quenched heavy hadron chiral
perturbation theory. Calculations are performed for three light flavors in the
isospin limit and additionally for two light non-degenerate flavors. We use
partially-quenched charge matrices that are easy to implement on the lattice.
The results presented are necessary for the light quark mass extrapolation and
zero-momentum extrapolation of lattice QCD and partially quenched lattice QCD
calculations of heavy hadron electromagnetic properties. Additionally relations
between the sextet electromagnetic form factors and transition form factors are
derived.Comment: 29 pages, 3 figures, RevTex
Doubly Heavy Baryons and Quark-Diquark Symmetry in Quenched and Partially Quenched Chiral Perturbation Theory
We extend the chiral Lagrangian with heavy quark-diquark symmetry to quenched
and partially quenched theories. These theories are used to derive formulae for
the chiral extrapolation of masses and hyperfine splittings of doubly heavy
baryons in lattice QCD simulations. A quark-diquark symmetry prediction for the
hyperfine splittings of heavy mesons and doubly heavy baryons is rather
insensitive to chiral corrections in both quenched and partially quenched QCD.
Extrapolation formulae for the doubly heavy baryon electromagnetic transition
moments are also determined for the partially quenched theory.Comment: 19pp, Ref. adde
Microstructural Modeling of Collagen Network Mechanics and Interactions with the Proteoglycan Gel in Articular Cartilage
Cartilage matrix mechanical function is largely determined by interactions between the collagen fibrillar network and the proteoglycan gel. Although the molecular physics of these matrix constituents have been characterized and modern imaging methods are capable of localized measurement of molecular densities and orientation distributions, theoretical tools for using this information for prediction of cartilage mechanical behavior are lacking. We introduce a means to model collagen network contributions to cartilage mechanics based upon accessible microstructural information (fibril density and orientation distributions) and which self-consistently follows changes in microstructural geometry with matrix deformations. The interplay between the molecular physics of the collagen network and the proteoglycan gel is scaled up to determine matrix material properties, with features such as collagen fibril pre-stress in free-swelling cartilage emerging naturally and without introduction of ad hoc parameters. Methods are developed for theoretical treatment of the collagen network as a continuum-like distribution of fibrils, such that mechanical analysis of the network may be simplified by consideration of the spherical harmonic components of functions of the fibril orientation, strain, and stress distributions. Expressions for the collagen network contributions to matrix stress and stiffness tensors are derived, illustrating that only spherical harmonic components of orders 0 and 2 contribute to the stress, while orders 0, 2, and 4 contribute to the stiffness. Depth- and compression-dependent equilibrium mechanical properties of cartilage matrix are modeled, and advantages of the approach are illustrated by exploration of orientation and strain distributions of collagen fibrils in compressed cartilage. Results highlight collagen-proteoglycan interactions, especially for very small physiological strains where experimental data are relatively sparse. These methods for determining matrix mechanical properties from measurable quantities at the microscale (composition, structure, and molecular physics) may be useful for investigating cartilage structure-function relationships relevant to load-bearing, injury, and repai
Baryon Masses in Partially Quenched Heavy Hadron Chiral Perturbation Theory
The masses of baryons containing a heavy quark are calculated to
next-to-leading order in partially quenched heavy hadron chiral perturbation
theory. Calculations are performed for three light flavors in the isospin limit
and additionally for two light non-degenerate flavors. The results presented
are necessary for extrapolating lattice QCD and partially quenched lattice QCD
calculations of the heavy hadron masses.Comment: 20 pages, 2 figures, RevTex
Equation of state SAHA-S meets stellar evolution code CESAM2k
We present an example of an interpolation code of the SAHA-S equation of
state that has been adapted for use in the stellar evolution code CESAM2k. The
aim is to provide the necessary data and numerical procedures for its
implementation in a stellar code. A technical problem is the discrepancy
between the sets of thermodynamic quantities provided by the SAHA-S equation of
state and those necessary in the CESAM2k computations. Moreover, the
independent variables in a practical equation of state (like SAHA-S) are
temperature and density, whereas for modelling calculations the variables
temperature and pressure are preferable. Specifically for the CESAM2k code,
some additional quantities and their derivatives must be provided. To provide
the bridge between the equation of state and stellar modelling, we prepare
auxiliary tables of the quantities that are demanded in CESAM2k. Then we use
cubic spline interpolation to provide both smoothness and a good approximation
of the necessary derivatives. Using the B-form of spline representation
provides us with an efficient algorithm for three-dimensional interpolation.
The table of B-spline coefficients provided can be directly used during stellar
model calculations together with the module of cubic spline interpolation. This
implementation of the SAHA-S equation of state in the CESAM2k stellar structure
and evolution code has been tested on a solar model evolved to the present. A
comparison with other equations of state is briefly discussed. The choice of a
regular net of mesh points for specific primary quantities in the SAHA-S
equation of state, together with accurate and consistently smooth tabulated
values, provides an effective algorithm of interpolation in modelling
calculations. The proposed module of interpolation procedures can be easily
adopted in other evolution codes.Comment: 8 pages, 5 figure
False-positive iodine-131 whole-body scan findings in patients with differentiated thyroid carcinoma: report of 11 cases and review of the literature
BACKGROUND: Iodine-131 (I-131) whole-body scan (WBS) plays an important role in the management of patients with differentiated thyroid carcinoma (DTC), to detect normal thyroid remnants and recurrent or metastatic disease. A focus of I-131 accumulation outside the thyroid bed and the areas of physiological uptake is strongly suggestive of a distant functioning metastasis. However, many false-positive I-131 WBS findings have been reported in the literature.
PATIENT FINDINGS: We describe a series of 11 personal cases of patients with DTC, collected from 1992 to 2011, in whom diagnostic or post-treatment WBS showed false-positive retention of I-131 in various locations.
SUMMARY: False-positive accumulations of I-131 on WBS may be classified according to the underlying pathophysiological mechanisms: external and internal contaminations by body secretions, ectopic normal thyroid and gastric tissues, inflammatory and infectious diseases, benign and malignant tumors, cysts and effusions of serous cavities, thymic uptake, and other non classified causes.
CONCLUSIONS: Clinicians must be aware of possible false-positive findings to avoid misinterpretations of the I-131 WBS, which could lead to inappropriate treatments
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