220 research outputs found
Pattern of gastric emptying in the pig: relation to feeding.
The aims of the present study were to compare the gastric emptying of dry matter (DM) and liquids during the feeding period with that following meal consumption, to clarify the relationship between feeding and gastric emptying, and to investigate how gastric emptying changes in growing animals. The studies were performed in pigs fitted with a gastric cannula and fed on a normal finely ground solid diet mixed with water containing CrEDTA as liquid marker. Gastric emptying was measured using a gastric evacuation technique. It was observed that between 0.75 and six hours after feeding the total amounts emptied increased, but the proportion of the meal emptied fell, with increase in meal size; emptying of both DM and liquids with large and small meals followed and exponential pattern. In contrast, while the animals were feeding, there was linear and rapid emptying of both DM and liquids following a very short (approximately two minutes) lag phase before emptying began. The rate of emptying increased linearly with body-weight (by 0.55 g DM/min and by 0.24 ml/min per kg body-weight over the range 58–200 kg), such that the emptying of digestible energy per kg metabolic body-weight (W0.75) was roughly maintained (between 2.9 and 3.2 kJ/min per kg W0.75). This suggests that the rate of emptying may be linked in some way with the metabolic requirements of the body. The biphasic pattern of gastric emptying observed is probably the intrinsic pattern of emptying of a meal which does not require breakdown of particles before emptying can occur
On Superspace Chern-Simons-like Terms
We search for superspace Chern-Simons-like higher-derivative terms in the low
energy effective actions of supersymmetric theories in four dimensions.
Superspace Chern-Simons-like terms are those gauge-invariant terms which cannot
be written solely in terms of field strength superfields and covariant
derivatives, but in which a gauge potential superfield appears explicitly. We
find one class of such four-derivative terms with N=2 supersymmetry which,
though locally on the Coulomb branch can be written solely in terms of field
strengths, globally cannot be. These terms are classified by certain Dolbeault
cohomology classes on the moduli space. We include a discussion of other
examples of terms in the effective action involving global obstructions on the
Coulomb branch.Comment: 23 pages; a reference and an author email correcte
High-energy gamma-ray emission from the inner jet of LS I+61 303: the hadronic contribution revisited
LS I+61 303 has been detected by the Cherenkov telescope MAGIC at very high
energies, presenting a variable flux along the orbital motion with a maximum
clearly separated from the periastron passage. In the light of the new
observational constraints, we revisit the discussion of the production of
high-energy gamma rays from particle interactions in the inner jet of this
system. The hadronic contribution could represent a major fraction of the TeV
emission detected from this source. The spectral energy distribution resulting
from p-p interactions is recalculated. Opacity effects introduced by the photon
fields of the primary star and the stellar decretion disk are shown to be
essential in shaping the high-energy gamma-ray light curve at energies close to
200 GeV. We also present results of Monte Carlo simulations of the
electromagnetic cascades developed very close to the periastron passage. We
conclude that a hadronic microquasar model for the gamma-ray emission in LS I
+61 303 can reproduce the main features of its observed high-energy gamma-ray
flux.Comment: 6 pages. Sligth improvements made. Accepted version by Astrophysics
and Space Scienc
Evaluation of bioadhesive capacity and immunoadjuvant properties of vitamin B(12)-Gantrez nanoparticles.
PURPOSE: To design bioadhesive Gantrez AN (poly[methyl vinyl ether-co-maleic
anhydride], PVM/MA) nanoparticles (NP) coated with Vitamin B12 (Vit B12), and
investigate their application in oral antigen delivery.
METHODS: The association of Vit B12 to Gantrez AN nanoparticles was performed by
the direct attachment of reactive Vit B12 to the surface of the nanoparticles (NPB), or
linking to the copolymer chains in dimethylformamide prior to NP formation (NPBDMF).
Nanoparticles were characterized by measuring the size, zeta potential, Vit B12
association efficacy, and stability of Vit B12 on the surface of the nanoparticles. In vivo
bioadhesion study was performed by the oral administration of fluorescently-labeled
nanoparticle formulations to rats. Both systemic and mucosal immune responses were
evaluated after oral and subcutaneous immunization with ovalbumin (OVA) containing
Vit B12-coated nanoparticles.
RESULTS: The Vit B12 nanoparticles displayed homogenous size distribution with a
mean diameter of about 200 nm and a negative surface charge. The association
efficiency of Vit B12 to NPB-DMF formulation was about two times higher than to the
NPB, showing also a higher surface stability of Vit B12. The bioadhesion study
demonstrated that NPB-DMF had an important tropism to the distal portions of the gut,
which was about 2 and 3.5 times higher than the tropism observed for NPB and control
NP, respectively (P< 0.05). Oral administration of OVA-NPB-DMF induced also
stronger and more balanced serum anti-OVA titers of IgG2a (Th1) and IgG1 (Th2)
compared to control OVA-NP. In addition, oral immunization with OVA-NPB-DMF
induced a higher mucosal IgA response than subcutaneous administration.
CONCLUSIONS: These results indicate the benefits of bioadhesive Vit B12-coated
nanoparticles in oral antigen delivery eliciting systemic and mucosal immune response
Higher-Derivative Terms in N=2 Supersymmetric Effective Actions
We show how to systematically construct higher-derivative terms in effective
actions in harmonic superspace despite the infinite redundancy in their
description due to the infinite number of auxiliary fields. Making an
assumption about the absence of certain superspace Chern-Simons-like terms
involving vector multiplets, we write all 3- and 4-derivative terms on Higgs,
Coulomb, and mixed branches. Among these terms are several with only
holomorphic dependence on fields, and at least one satisfies a
non-renormalization theorem. These holomorphic terms include a novel
3-derivative term on mixed branches given as an integral over 3/4 of
superspace. As an illustration of our method, we search for Wess-Zumino terms
in the low energy effective action of N=2 supersymmetric QCD. We show that such
terms occur only on mixed branches. We also present an argument showing that
the combination of space-time locality with supersymmetry implies locality in
the anticommuting superspace coordinates of for unconstrained superfields.Comment: 30 pages. Added references and simplified final form of WZ ter
High Energy QCD: Stringy Picture from Hidden Integrability
We discuss the stringy properties of high-energy QCD using its hidden
integrability in the Regge limit and on the light-cone. It is shown that
multi-colour QCD in the Regge limit belongs to the same universality class as
superconformal =2 SUSY YM with at the strong coupling
orbifold point. The analogy with integrable structure governing the low energy
sector of =2 SUSY gauge theories is used to develop the brane picture
for the Regge limit. In this picture the scattering process is described by a
single M2 brane wrapped around the spectral curve of the integrable spin chain
and unifying hadrons and reggeized gluons involved in the process. New
quasiclassical quantization conditions for the complex higher integrals of
motion are suggested which are consistent with the duality of the
multi-reggeon spectrum. The derivation of the anomalous dimensions of the
lowest twist operators is formulated in terms of the Riemann surfacesComment: 37 pages, 3 figure
Caged Black Holes: Black Holes in Compactified Spacetimes I -- Theory
In backgrounds with compact dimensions there may exist several phases of
black objects including the black-hole and the black-string. The phase
transition between them raises puzzles and touches fundamental issues such as
topology change, uniqueness and Cosmic Censorship. No analytic solution is
known for the black hole, and moreover, one can expect approximate solutions
only for very small black holes, while the phase transition physics happens
when the black hole is large. Hence we turn to numerical solutions. Here some
theoretical background to the numerical analysis is given, while the results
will appear in a forthcoming paper. Goals for a numerical analysis are set. The
scalar charge and tension along the compact dimension are defined and used as
improved order parameters which put both the black hole and the black string at
finite values on the phase diagram. Predictions for small black holes are
presented. The differential and the integrated forms of the first law are
derived, and the latter (Smarr's formula) can be used to estimate the ``overall
numerical error''. Field asymptotics and expressions for physical quantities in
terms of the numerical ones are supplied. Techniques include ``method of
equivalent charges'', free energy, dimensional reduction, and analytic
perturbation for small black holes.Comment: 23 pages. v3: version to be published in PRD, 3 references adde
New black holes in the brane-world?
It is known that the Einstein field equations in five dimensions admit more
general spherically symmetric black holes on the brane than four-dimensional
general relativity. We propose two families of analytic solutions (with
g_tt\not=-1/g_rr), parameterized by the ADM mass and the PPN parameter beta,
which reduce to Schwarzschild for beta=1. Agreement with observations requires
|\beta-1| |\eta|<<1. The sign of eta plays a key role in the global causal
structure, separating metrics which behave like Schwarzschild (eta<0) from
those similar to Reissner-Nordstroem (eta>0). In the latter case, we find a
family of black hole space-times completely regular.Comment: 4 pages, RevTeX, 3 eps figures, final version to appear in Phys. Rev.
Schwarzschild Solution on the Brane
In this communication we have shown that Schwarzschild solution is possible
in brane world for some specific choices of brane matter and the non local
effects from the bulk. A conformally flat bulk space time with fine-tuned
vacuum energy (brane tension) shows that, Schwarzschild solution may also be
the vacuum solution for brane world scenario.Comment: 3 page
The Scale of Cosmic Isotropy
The most fundamental premise to the standard model of the universe, the
Cosmological Principle (CP), states that the large-scale properties of the
universe are the same in all directions and at all comoving positions.
Demonstrating this theoretical hypothesis has proven to be a formidable
challenge. The cross-over scale R_{iso} above which the galaxy distribution
becomes statistically isotropic is vaguely defined and poorly (if not at all)
quantified. Here we report on a formalism that allows us to provide an
unambiguous operational definition and an estimate of R_{iso}. We apply the
method to galaxies in the Sloan Digital Sky Survey (SDSS) Data Release 7,
finding that R_{iso}\sim 150h^{-1} Mpc. Besides providing a consistency test of
the Copernican principle, this result is in agreement with predictions based on
numerical simulations of the spatial distribution of galaxies in cold dark
matter dominated cosmological models.Comment: 15 pages, 4 figures, accepted by JCAP. The text matches the published
versio
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