465 research outputs found
Suppression of nuclear factor-κB activity in macrophages by chylomicron remnants: modulation by the fatty acid composition of the particles
Current evidence indicates that chylomicron remnants (CMR) induce macrophage foam cell formation, an early event in atherosclerosis. Inflammation also plays a part in atherogenesis and the transcription factor nuclear factor-κB (NF-κB) has been implicated. In this study, the influence of CMR on the activity of NF-κB in macrophages and its modulation by the fatty acid composition of the particles were investigated using macrophages derived from the human monocyte cell line THP-1 and CMR-like particles (CRLPs). Incubation of THP-1 macrophages with CRLPs caused decreased NF-κB activation and downregulated the expression of phospho-p65–NF-κB and phospho-IκBα (pIκBα). Secretion of the inflammatory cytokines tumour necrosis factor α, interleukin-6 and monocyte chemoattractant protein-1, which are under NF-κB transcriptional control, was inhibited and mRNA expression for cyclooxygenase-2, an NF-κB target gene, was reduced. CRLPs enriched in polyunsaturated fatty acids compared with saturated or monounsaturated fatty acids had a markedly greater inhibitory effect on NF-κB binding to DNA and the expression of phospho-p65–NF-κB and pIκB. Lipid loading of macrophages with CRLPs enriched in polyunsaturated fatty acids compared with monounsaturated fatty acids or saturated fatty acids also increased the subsequent rate of cholesterol efflux, an effect which may be linked to the inhibition of NF-κB activity. These findings demonstrate that CMR suppress NF-κB activity in macrophages, and that this effect is modulated by their fatty acid composition. This downregulation of inflammatory processes in macrophages may represent a protective effect of CMR which is enhanced by dietary polyunsaturated fatty acids
Entropy of Lovelock Black Holes
A general formula for the entropy of stationary black holes in Lovelock
gravity theories is obtained by integrating the first law of black hole
mechanics, which is derived by Hamiltonian methods. The entropy is not simply
one quarter of the surface area of the horizon, but also includes a sum of
intrinsic curvature invariants integrated over a cross section of the horizon.Comment: 15 pages, plain Latex, NSF-ITP-93-4
Gravitation with superposed Gauss--Bonnet terms in higher dimensions: Black hole metrics and maximal extensions
Our starting point is an iterative construction suited to combinatorics in
arbitarary dimensions d, of totally anisymmetrised p-Riemann 2p-forms (2p\le d)
generalising the (1-)Riemann curvature 2-forms. Superposition of p-Ricci
scalars obtained from the p-Riemann forms defines the maximally Gauss--Bonnet
extended gravitational Lagrangian. Metrics, spherically symmetric in the (d-1)
space dimensions are constructed for the general case. The problem is directly
reduced to solving polynomial equations. For some black hole type metrics the
horizons are obtained by solving polynomial equations. Corresponding Kruskal
type maximal extensions are obtained explicitly in complete generality, as is
also the periodicity of time for Euclidean signature. We show how to include a
cosmological constant and a point charge. Possible further developments and
applications are indicated.Comment: 13 pages, REVTEX. References and Note Adde
Culture, Embodiment and Genes: Unravelling the Triple Helix
Much recent work stresses the role of embodiment and action in thought and reason, and celebrates the power of transmitted cultural and environmental structures to transform the problem-solving activity required of individual brains. By apparent contrast, much work in evolutionary psychology has stressed the selective fit of the biological brain to an ancestral environment of evolutionary adaptedness, with an attendant stress upon the limitations and cognitive biases that result. On the face of it, this suggests either a tension or, at least, a mismatch, with the symbiotic dyad of cultural evolution and embodied cognition. In what follows, we explore this mismatch by focusing on three key ideas: cognitive niche construction; cognitive modularity; and the existence (or otherwise) of an evolved universal human nature. An appreciation of the power and scope of the first, combined with consequently more nuanced visions of the latter two, allow us to begin to glimpse a much richer vision of the combined interactive potency of biological and cultural evolution for active, embodied agents
Plant Growth Optimization by Vegetable Production System in HI-SEAS Analog Habitat
The Vegetable Production System (Veggie) is a scientific payload designed to support plant growth for food production under microgravity conditions. The configuration of Veggie consists of an LED lighting system with modular rooting pillows designed to contain substrate media and time-release fertilizer. The pillows were designed to be watered passively using capillary principles but have typically been watered manually by the astronauts in low-Earth orbit (LEO). The design of Veggie allows cabin air to be drawn through the plant enclosure for thermal and humidity control and for supplying CO2 to the plants. Since its delivery to the International Space Station (ISS) in 2014, Veggie has undergone several experimental trials by various crews. Ground unit testing of Veggie was conducted during an 8-month Mars analog study in a semi-contained environment of a simulated habitat located at approximately 8,200 feet (2,500 m) elevation on the Mauna Loa volcano on the Island of Hawaii. The Hawaii Space Exploration Analog and Simulation (HI-SEAS) offered conditions (habitat, mission, communications, etc.) intended to simulate a planetary exploration mission. This paper provides data and analyses to show the prospect for optimized use of the current Veggie design for human habitats. Lessons learned during the study may provide opportunities for updating the system design and operational parameters for current Veggie experiments being conducted onboard the ISS and for payloads on future deep space missions
Geometrothermodynamics of five dimensional black holes in Einstein-Gauss-Bonnet-theory
We investigate the thermodynamic properties of 5D static and spherically
symmetric black holes in (i) Einstein-Maxwell-Gauss-Bonnet theory, (ii)
Einstein-Maxwell-Gauss-Bonnet theory with negative cosmological constant, and
in (iii) Einstein-Yang-Mills-Gauss-Bonnet theory. To formulate the
thermodynamics of these black holes we use the Bekenstein-Hawking entropy
relation and, alternatively, a modified entropy formula which follows from the
first law of thermodynamics of black holes. The results of both approaches are
not equivalent. Using the formalism of geometrothermodynamics, we introduce in
the manifold of equilibrium states a Legendre invariant metric for each black
hole and for each thermodynamic approach, and show that the thermodynamic
curvature diverges at those points where the temperature vanishes and the heat
capacity diverges.Comment: New sections added, references adde
Generalised Israel Junction Conditions for a Gauss-Bonnet Brane World
In spacetimes of dimension greater than four it is natural to consider higher
order (in R) corrections to the Einstein equations. In this letter generalized
Israel junction conditions for a membrane in such a theory are derived. This is
achieved by generalising the Gibbons-Hawking boundary term. The junction
conditions are applied to simple brane world models, and are compared to the
many contradictory results in the literature.Comment: 4 page
Field Theoretical Quantum Effects on the Kerr Geometry
We study quantum aspects of the Einstein gravity with one time-like and one
space-like Killing vector commuting with each other. The theory is formulated
as a \coset nonlinear -model coupled to gravity. The quantum analysis
of the nonlinear -model part, which includes all the dynamical degrees
of freedom, can be carried out in a parallel way to ordinary nonlinear
-models in spite of the existence of an unusual coupling. This means
that we can investigate consistently the quantum properties of the Einstein
gravity, though we are limited to the fluctuations depending only on two
coordinates. We find the forms of the beta functions to all orders up to
numerical coefficients. Finally we consider the quantum effects of the
renormalization on the Kerr black hole as an example. It turns out that the
asymptotically flat region remains intact and stable, while, in a certain
approximation, it is shown that the inner geometry changes considerably however
small the quantum effects may be.Comment: 16 pages, LaTeX. The hep-th number added on the cover, and minor
typos correcte
Gauss-Bonnet Black Holes in dS Spaces
We study the thermodynamic properties associated with black hole horizon and
cosmological horizon for the Gauss-Bonnet solution in de Sitter space. When the
Gauss-Bonnet coefficient is positive, a locally stable small black hole appears
in the case of spacetime dimension , the stable small black hole
disappears and the Gauss-Bonnet black hole is always unstable quantum
mechanically when . On the other hand, the cosmological horizon is
found always locally stable independent of the spacetime dimension. But the
solution is not globally preferred, instead the pure de Sitter space is
globally preferred. When the Gauss-Bonnet coefficient is negative, there is a
constraint on the value of the coefficient, beyond which the gravity theory is
not well defined. As a result, there is not only an upper bound on the size of
black hole horizon radius at which the black hole horizon and cosmological
horizon coincide with each other, but also a lower bound depending on the
Gauss-Bonnet coefficient and spacetime dimension. Within the physical phase
space, the black hole horizon is always thermodynamically unstable and the
cosmological horizon is always stable, further, as the case of the positive
coefficient, the pure de Sitter space is still globally preferred. This result
is consistent with the argument that the pure de Sitter space corresponds to an
UV fixed point of dual field theory.Comment: Rextex, 17 pages including 8 eps figures, v2: minor changes, to
appear in PRD, v3: references adde
Жанр эссе полемического характера в публицистическом дискурсе А. Андреева
The accuracy of synoptic-based weather forecasting deteriorates rapidly after five days and is not routinely available beyond 10 days. Conversely, climate forecasts are generally not feasible for periods of less than 3 months, resulting in a weather-climate gap. The tropical atmospheric phenomenon known as the Madden-Julian Oscillation (MJO) has a return interval of 30 to 80 days that might partly fill this gap. Our near-global analysis demonstrates that the MJO is a significant phenomenon that can influence daily rainfall patterns, even at higher latitudes, via teleconnections with broadscale mean sea level pressure (MSLP) patterns. These weather states provide a mechanistic basis for an MJO-based forecasting capacity that bridges the weather-climate divide. Knowledge of these tropical and extra-tropical MJO-associated weather states can significantly improve the tactical management of climate-sensitive systems such as agriculture
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