462 research outputs found
The role of adenosine in chondrocyte death in murine osteoarthritis and in a murine chondrocyte cell line
SummaryObjectiveTo investigate the role of adenosine in chondrocyte death in murine osteoarthritis (OA).Methods5âČ-Nucleotidase (5âČNT) generates adenosine. Enzyme activity was measured histochemically in normal murine and osteoarthritic STR/ort strain tibial cartilage. Adenosine-mediated cell death was investigated in MC615 chondrocyte cultures. Adenosine receptors (ARs) were assessed by reverse transcriptase polymerase chain reaction (RT-PCR). Cellular uptake of [3H] adenosine was measured with or without the inhibitor, nitrobenzylthioinosine (NBTI). Cell death was assessed by cell counting and DNA laddering following selective receptor stimulation, or after modulating adenosine metabolism with adenosine deaminase (ADA) or adenosine kinase (AK) inhibitors [erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) and Iodotubericidin (Itub)], or with homocysteine (HC). Markers of apoptosis were assessed by Western blotting. Cell studies were validated by incubating normal murine knee joints in a medium containing adenosine and metabolic inhibitors. Apoptotic chondrocytes were identified with the TUNEL reaction.Results5âČNT activity in STR/ort tibial cartilage increased with development of OA, especially close to OA lesions. Adenosine induced MC615 cell death in the presence of ADA inhibition (100ÎŒM EHNA), or 1mM HC, or both. Adenosine uptake, mediated by NBTI-sensitive adenosine transporters, was required for cell death. ARs were expressed (A2b>A2a>A1) but were not involved in mediating cell death. Cell death involved the activation of caspase-3 and DNA fragmentation and was prevented by inhibiting caspase activity. However, neither caspase-8 nor caspase-9 was detected. Adenosine+EHNA induced chondrocyte apoptosis in normal murine knee joints.ConclusionIncreased adenosine production may induce chondrocyte apoptosis and play a role in OA in STR/ort mice
Hidden Symmetries and Integrable Hierarchy of the N=4 Supersymmetric Yang-Mills Equations
We describe an infinite-dimensional algebra of hidden symmetries of N=4
supersymmetric Yang-Mills (SYM) theory. Our derivation is based on a
generalization of the supertwistor correspondence. Using the latter, we
construct an infinite sequence of flows on the solution space of the N=4 SYM
equations. The dependence of the SYM fields on the parameters along the flows
can be recovered by solving the equations of the hierarchy. We embed the N=4
SYM equations in the infinite system of the hierarchy equations and show that
this SYM hierarchy is associated with an infinite set of graded symmetries
recursively generated from supertranslations. Presumably, the existence of such
nonlocal symmetries underlies the observed integrable structures in quantum N=4
SYM theory.Comment: 24 page
6Li direct breakup lifetimes
alpha-d coincidence data were studied for the 6Li + 59Co reaction at E(lab) =
29.6 MeV. By using a kinematic analysis, it was possible to identify which
process, leading to the same final state, has the major contribution for each
of the selected angular regions. Contributions of the 6Li sequential and direct
breakup to the incomplete fusion/transfer process were discussed by considering
the lifetimes obtained by using a semiclassical approach, for both breakup
components.Comment: 5 pages, 4 figures, Invited Talk (Parrallel Sessions) of A. Szanto de
Toledo, prepared for the Proccedings of the 10th International Conference on
Nucleus-Nucleus Collisions, August 16-21, 2009, Beijing, China; submitted to
Nucl. Phys. A (Proceedings of NN2009
Quantisation of twistor theory by cocycle twist
We present the main ingredients of twistor theory leading up to and including
the Penrose-Ward transform in a coordinate algebra form which we can then
`quantise' by means of a functorial cocycle twist. The quantum algebras for the
conformal group, twistor space CP^3, compactified Minkowski space CMh and the
twistor correspondence space are obtained along with their canonical quantum
differential calculi, both in a local form and in a global *-algebra
formulation which even in the classical commutative case provides a useful
alternative to the formulation in terms of projective varieties. We outline how
the Penrose-Ward transform then quantises. As an example, we show that the
pull-back of the tautological bundle on CMh pulls back to the basic instanton
on S^4\subset CMh and that this observation quantises to obtain the
Connes-Landi instanton on \theta-deformed S^4 as the pull-back of the
tautological bundle on our \theta-deformed CMh. We likewise quantise the
fibration CP^3--> S^4 and use it to construct the bundle on \theta-deformed
CP^3 that maps over under the transform to the \theta-deformed instanton.Comment: 68 pages 0 figures. Significant revision now has detailed formulae
for classical and quantum CP^
Vegetation and floristics of a lowland tropical rainforest in northeast Australia
Background: Full floristic data, tree demography, and biomass estimates incorporating non-tree life forms are seldom collected and reported for forest plots in the tropics. Established research stations serve as important repositories of such biodiversity and ecological data. With a canopy crane setup within a tropical lowland rainforest estate, the 42-ha Daintree Rainforest Observatory (DRO) in Cape Tribulation, northern Australia is a research facility of international significance. We obtained an estimate of the vascular plant species richness for the site, by surveying all vascular plant species from various mature-phase, remnant and open vegetation patches within the site. We also integrate and report the demography and basal areas of trees â„ 10 cm diameter at breast height (dbh) in a new 1- ha core plot, an extension to the pre-existing forest 1-ha plot under the canopy crane. In addition, we report for the canopy crane plot new demography and basal areas for smaller size shrubs and treelets subsampled from nine 20 m quadrats, and liana basal area and abundance from the whole plot. The DRO site has an estimated total vascular plant species richness of 441 species, of which 172 species (39%) are endemic to Australia, and 4 species are endemics to the Daintree region. The 2 x 1-ha plots contains a total of 262 vascular plant species of which 116 (1531 individuals) are tree species â„ 10 cm dbh. We estimate a stem basal area of 34.9 m ha, of which small stems (tree saplings and shrubs <10cm dbh) and lianas collectively contribute c.4.2%. Comparing the stem density-diversity patterns of the DRO forest with other tropical rainforests globally, our meta-analysis shows that DRO forests has a comparatively high stem density and moderate species diversity, due to the influence of cyclones. These data will provide an important foundation for ecological and conservation studies in lowland tropical forest.
New information: We present a floristic checklist, a life form breakdown, and demography data from two 1-ha rainforest plots from a lowland tropical rainforest study site. We also present a meta-analysis of stem densities and species diversity from comparable-sized plots across the tropics
Partially filled stripes in the two dimensional Hubbard model: statics and dynamics
The internal structure of stripes in the two dimensional Hubbard model is
studied by going beyond the Hartree-Fock approximation. Partially filled
stripes, consistent with experimental observations, are stabilized by quantum
fluctuations, included through the Configuration Interaction method. Hopping of
short regions of the stripes in the transverse direction is comparable to the
bare hopping element. The integrated value of compares well
with experimental results.Comment: 4 page
A Performance Analysis Framework for WiFi/WiMAX Heterogeneous Metropolitan Networks Based on Cross-Layer Design
The communication between network nodes within different protocol domains is often regarded simply as a black box with unknown configuration conditions in the path. We address network heterogeneity using a white box approach and focus on its interconnection processes. To achieve this purpose, a Performance Analysis Framework (PAF) is proposed which is composed of the formalization of the latter using process algebra (PA) and the corresponding teletraffic performance models. In this contribution, we target the IEEE 802.16 and IEEE 802.11 protocols. For the teletraffic models, we extend previous models for such scenario with the inclusion of the following protocol operational parameters (metrics): bit error rate (BER), packet error ratio (PER), and packet length (pl). From the framework teletraffic models, the optimal packet length (OPL), end to end throughput, delay, and packet loss are obtained. The PAF outperforms previous modeling solutions in terms of delay and throughput relative to NS3 simulation results. </jats:p
Non-destructive assessment of the oxidative stability of intact macadamia nuts during the drying process by near-infrared spectroscopy
We have developed a rapid non-destructive method to assess the oxidative stability of intact macadamia nuts using near-infrared spectroscopy (NIRS). Intact macadamia nuts of the cultivars HAES 344 âKauâ, HAES 660 âKeaauâ, IAC 4â12âŻB, and IAC Campinas B were harvested and immediately oven-dried for 4 days at 30âŻÂ°C, 2 days at 40âŻÂ°C, and 1 day at 60âŻÂ°C to achieve 1.5% kernel moisture content. At each drying step nuts were withdrawn and their moisture content, peroxide value (PV), and acidity index (AI) determined. The best partial least square model for PV prediction was obtained using the Savitzky-Golay (SG) second derivative resulting in a standard error of prediction (SEP) of 0.55 meq·kgâ1 and a coefficient of determination (R2C) of 0.57. The best AI prediction-model result was obtained using the SG second derivative (SEPâŻ=âŻ0.14%, R2CâŻ=âŻ0.29). Based on the maximum quality limits of 3 meq·kgâ1 for PV and 0.5% for AI, the SEP values represented 18% and 28%, respectively. Therefore, the prediction method can be considered useful since the errors are lower than the quality limits. Thus, NIRS can be used to assess the oxidative stability of intact macadamia kernels
The measurement of commitment to work
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43493/1/11111_2004_Article_BF00972537.pd
A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007
We present the results of the first search for gravitational wave bursts
associated with high energy neutrinos. Together, these messengers could reveal
new, hidden sources that are not observed by conventional photon astronomy,
particularly at high energy. Our search uses neutrinos detected by the
underwater neutrino telescope ANTARES in its 5 line configuration during the
period January - September 2007, which coincided with the fifth and first
science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed
for candidate gravitational-wave signals coincident in time and direction with
the neutrino events. No significant coincident events were observed. We place
limits on the density of joint high energy neutrino - gravitational wave
emission events in the local universe, and compare them with densities of
merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at
http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access
area to figures, tables at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000
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