211 research outputs found
Equilibration through local information exchange in networks
We study the equilibrium states of energy functions involving a large set of
real variables, defined on the links of sparsely connected networks, and
interacting at the network nodes, using the cavity and replica methods. When
applied to the representative problem of network resource allocation, an
efficient distributed algorithm is devised, with simulations showing full
agreement with theory. Scaling properties with the network connectivity and the
resource availability are found.Comment: v1: 7 pages, 1 figure, v2: 4 pages, 2 figures, simplified analysis
and more organized results, v3: minor change
The effect of dietary fish oil-supplementation to healthy young men on oxidative burst measured by whole blood chemiluminescence
PEMFC MEA and System Design Considerations
Proton exchange membrane fuel cells (PEMFCs) are being developed and sold commercially for multiple near term markets. Ballard Power Systems is focused on the near term markets of backup power, distributed generation, materials handling, and buses. Significant advances have been made in cost and durability of fuel cell products. Improved tolerance to a wide range of system operation and environmental noises will enable increased viability across a broad range of applications. In order to apply the most effective membrane electrode assembly (MEA) design for each market, the system requirements and associated MEA failures must be well understood. The failure modes associated with the electrodes and membrane degradation are discussed with respect to associated system operation and mitigating approaches. A few key system considerations that influence MEA design include expected fuel quality, balance-of-plant materials, time under idle or open circuit operation, and start-up and shut-down conditions
Quantization of Hyperbolic N-Sphere Scattering Systems in Three Dimensions
Most discussions of chaotic scattering systems are devoted to two-dimensional
systems. It is of considerable interest to extend these studies to the, in
general, more realistic case of three dimensions. In this context, it is
conceptually important to investigate the quality of semiclassical methods as a
function of the dimensionality. As a model system, we choose various three
dimensional generalizations of the famous three disk problem which played a
central role in the study of chaotic scattering in two dimensions. We present a
quantum-mechanical treatment of the hyperbolic scattering of a point particle
off a finite number of non-overlapping and non-touching hard spheres in three
dimensions. We derive expressions for the scattering matrix S and its
determinant. The determinant of S decomposes into two parts, the first one
contains the product of the determinants of the individual one-sphere
S-matrices and the second one is given by a ratio involving the determinants of
a characteristic KKR-type matrix and its conjugate. We justify our approach by
showing that all formal manipulations in these derivations are correct and that
all the determinants involved which are of infinite dimension exist. Moreover,
for all complex wave numbers, we conjecture a direct link between the
quantum-mechanical and semiclassical descriptions: The semiclassical limit of
the cumulant expansion of the KKR-type matrix is given by the Gutzwiller-Voros
zeta function plus diffractional corrections in the curvature expansion. This
connection is direct since it is not based on any kind of subtraction scheme
involving bounded reference systems. We present numerically computed resonances
and compare them with the corresponding data for the similar two-dimensional
N-disk systems and with semiclassical calculations.Comment: 35 pages, LaTeX plus 8 Postscript figures, uses epsf.sty, epsfig.sty
and epsf.te
Contraction and AICAR Stimulate IL-6 Vesicle Depletion From Skeletal Muscle Fibers In Vivo
Recent studies suggest that interleukin 6 (IL-6) is released from contracting skeletal muscles; however, the cellular origin, secretion kinetics, and signaling mechanisms regulating IL-6 secretion are unknown. To address these questions, we developed imaging methodology to study IL-6 in fixed mouse muscle fibers and in live animals in vivo. Using confocal imaging to visualize endogenous IL-6 protein in fixed muscle fibers, we found IL-6 in small vesicle structures distributed throughout the fibers under basal (resting) conditions. To determine the kinetics of IL-6 secretion, intact quadriceps muscles were transfected with enhanced green fluorescent protein (EGFP)-tagged IL-6 (IL-6-EGFP), and 5 days later anesthetized mice were imaged before and after muscle contractions in situ. Contractions decreased IL-6-EGFP–containing vesicles and protein by 62% (P < 0.05), occurring rapidly and progressively over 25 min of contraction. However, contraction-mediated IL-6-EGFP reduction was normal in muscle-specific AMP-activated protein kinase (AMPK) α2-inactive transgenic mice. In contrast, the AMPK activator AICAR decreased IL-6-EGFP vesicles, an effect that was inhibited in the transgenic mice. In conclusion, resting skeletal muscles contain IL-6–positive vesicles that are expressed throughout myofibers. Contractions stimulate the rapid reduction of IL-6 in myofibers, occurring through an AMPKα2-independent mechanism. This novel imaging methodology clearly establishes IL-6 as a contraction-stimulated myokine and can be used to characterize the secretion kinetics of other putative myokines
Nutrient-limited subarctic caves harbour more diverse and complex bacterial communities than their surface soil
Background: Subarctic regions are particularly vulnerable to climate change, yet little is known about nutrient
availability and biodiversity of their cave ecosystems. Such knowledge is crucial for predicting the vulnerability of
these ecosystems to consequences of climate change. Thus, to improve our understanding of life in these habitats,
we characterized environmental variables, as well as bacterial and invertebrate communities of six subarctic caves in
Northern Norway.
Results: Only a minuscule diversity of surface-adapted invertebrates were found in these caves. However, the bacte‑
rial communities in caves were compositionally diferent, more diverse and more complex than the nutrient-richer
surface soil. Cave soil microbiomes were less variable between caves than between surface communities in the same
area, suggesting that the stable cave environments with tougher conditions drive the uniform microbial communi‑
ties. We also observed only a small proportion of cave bacterial genera originating from the surface, indicating unique
cave-adapted microbial communities. Increased diversity within caves may stem from higher niche specialization and
levels of interdependencies for nutrient cycling among bacterial taxa in these oligotrophic environments.
Conclusions: Taken together this suggest that environmental changes, e.g., faster melting of snow as a result of
global warming that could alter nutrient infux, can have a detrimental impact on interactions and dependencies of
these complex communities. This comparative exploration of cave and surface microbiomes also lays the founda‑
tion to further investigate the long-term environmental variables that shape the biodiversity of these vulnerable
ecosystems.info:eu-repo/semantics/publishedVersio
Sub-Clinical Cognitive Decline and Resting Cerebral Blood Flow in Middle Aged Men
Although dementia is associated with both global and regional cerebral blood flow
(CBF) changes, little is known about cerebral perfusion in the early pre-clinical
stages of cognitive decline preceding overt cognitive dysfunction. The aim of this
study was to investigate the association of early sub-clinical cognitive decline with
CBF.
The study participants were recruited from a cohort of Danish men born in 1953.
Based on a regression model we selected men who performed better (Group A,
n=94) and poorer (Group B, n=95) on cognitive testing at age 57 than expected
from testing at age 20. Participants underwent supplementary cognitive testing,
blood sampling and MRI including measurements of regional and global CBF.
Regional CBF was lower in group B than in group A in the posterior cingulate gyrus
and the precuneus. The associations were attenuated when corrected for global
atrophy, but remained significant in regions of interest based analysis adjusting for
regional gray matter volume and vascular risk factors. No influence of group on
global CBF was observed.
We conclude that early sub-clinical cognitive decline is associated with reduced
perfusion in the precuneus and posterior cingulate gyrus independently of
regional atrophy and vascular risk factors, but cannot be statistically separated
from an association with global atrophy
A randomized study of the effect of fish oil on n-3 fatty acid incorporation and nutritional status in lung cancer patients
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