1,009 research outputs found

### Effect of different omega-6/omega-3 polyunsaturated fatty acid ratios on the formation of monohydroxylated fatty acids in THP-1 derived macrophages

Omega-6 and omega-3 polyunsaturated fatty acids (n-6 and n-3 PUFA) can modulate inflammatory processes. In western diets, the content of n-6 PUFA is much higher than that of n-3 PUFA, which has been suggested to promote a pro-inflammatory phenotype. The aim of this study was to analyze the effect of modulating the n-6/n-3 PUFA ratio on the formation of monohydroxylated fatty acid (HO-FAs) derived from the n-6 PUFA arachidonic acid (AA) and the n-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in THP-1 macrophages by means of LC-MS. Lipid metabolites were measured in THP-1 macrophage cell pellets. The concentration of AA-derived hydroxyeicosatetraenoic acids (HETEs) was not significantly changed when incubated THP-1 macrophages in a high AA/(EPA+DHA) ratio of 19/1 vs. a low ratio AA/(EPA+DHA) of 1/1 (950.6 +/- 110 ng/mg vs. 648.2 +/- 92.4 ng/mg, p = 0.103). Correspondingly, the concentration of EPA-derived hydroxyeicosapentaenoic acids (HEPEs) and DHA-derived hydroxydocosahexaenoic acids (HDHAs) were significantly increased (63.9 +/- 7.8 ng/mg vs. 434.4 +/- 84.3 ng/mg, p = 0.012 and 84.9 +/- 18.3 ng/mg vs. 439.4 +/- 82.7 ng/mg, p = 0.014, respectively). Most notable was the strong increase of 18-hydroxyeicosapentaenoic acid (18-HEPE) formation in THP-1 macrophages, with levels of 170.9 +/- 40.2 ng/mg protein in the high n-3 PUFA treated cells. Thus our data indicate that THP-1 macrophages prominently utilize EPA and DHA for monohydroxylated metabolite formation, in particular 18-HEPE, which has been shown to be released by macrophages to prevent pressure overload-induced maladaptive cardiac remodeling

### Simulated-tempering approach to spin-glass simulations

After developing an appropriate iteration procedure for the determination of
the parameters, the method of simulated tempering has been successfully applied
to the 2D Ising spin glass. The reduction of the slowing down is comparable to
that of the multicanonical algorithm. Simulated tempering has, however, the
advantages to allow full vectorization of the programs and to provide the
canonical ensemble directly.Comment: 12 pages (LaTeX), 4 postscript figures, uufiles encoded, submitted to
Physical Review

### Pion photoproduction on the nucleon in the quark model

We present a detailed quark-model study of pion photoproduction within the
effective Lagrangian approach. Cross sections and single-polarization
observables are investigated for the four charge channels, $\gamma p\to \pi^+
n$, $\gamma n\to \pi^- p$, $\gamma p\to \pi^0 p$, and $\gamma n\to \pi^0 n$.
Leaving the $\pi N\Delta$ coupling strength to be a free parameter, we obtain a
reasonably consistent description of these four channels from threshold to the
first resonance region. Within this effective Lagrangian approach, strongly
constrainted by the quark model, we consider the issue of double-counting which
may occur if additional {\it t}-channel contributions are included.Comment: Revtex, 35 pages, 16 eps figures; version to appear on PR

### Cluster Spin Glass Distribution Functions in La$_{2-x}$Sr$_x$CuO$_4$

Signatures of the cluster spin glass have been found in a variety of
experiments, with an effective onset temperature $T_{on}$ that is frequency
dependent. We reanalyze the experimental results and find that they are
characterized by a distribution of activation energies, with a nonzero glass
transition temperature $T_g(x)<T_{on}$. While the distribution of activation
energies is the same, the distribution of weights depends on the process.
Remarkably, the weights are essentially doping independent.Comment: 5 pages, 5 ps figure

### Low frequency response of a collectively pinned vortex manifold

A low frequency dynamic response of a vortex manifold in type-II
superconductor can be associated with thermally activated tunneling of large
portions of the manifold between pairs of metastable states (two-level
systems). We suggest that statistical properties of these states can be
verified by using the same approach for the analysis of thermal fluctuations
the behaviour of which is well known. We find the form of the response for the
general case of vortex manifold with non-dispersive elastic moduli and for the
case of thin superconducting film for which the compressibility modulus is
always non-local.Comment: 8 pages, no figures, ReVTeX, the final version. Text strongly
modified, all the results unchange

### Superconducting Transition Temperature in Heterogeneous Ferromagnet-Superconductor Systems

We study the shift of the the superconducting transition temperature $T_c$ in
ferromagnetic-superconducting bi-layers and in a superconducting film supplied
a square array of ferromagnetic dots. We find that the transition temperature
in these two cases change presumably in opposite direction and that its change
is not too small. We extend these results to multilayer structures. We predict
that rather small external magnetic field $\sim 10$ Oe can change the
transition temperature of the bilayer by 10% .Comment: 9 pages, 2 figure

### Quantum field theory of metallic spin glasses

We introduce an effective field theory for the vicinity of a zero temperature
quantum transition between a metallic spin glass (``spin density glass'') and a
metallic quantum paramagnet. Following a mean field analysis, we perform a
perturbative renormalization-group study and find that the critical properties
are dominated by static disorder-induced fluctuations, and that dynamic
quantum-mechanical effects are dangerously irrelevant. A Gaussian fixed point
is stable for a finite range of couplings for spatial dimensionality $d > 8$,
but disorder effects always lead to runaway flows to strong coupling for $d
\leq 8$. Scaling hypotheses for a {\em static\/} strong-coupling critical field
theory are proposed. The non-linear susceptibility has an anomalously weak
singularity at such a critical point. Although motivated by a perturbative
study of metallic spin glasses, the scaling hypotheses are more general, and
could apply to other quantum spin glass to paramagnet transitions.Comment: 16 pages, REVTEX 3.0, 2 postscript figures; version contains
reference to related work in cond-mat/950412

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