35 research outputs found
A note on spin chain/string duality
Recently a significant progress in matching the anomalous dimensions of
certain class of operators in N=4 SYM theory and rotating strings was made. The
correspondence was established mainly using Bethe ansatz technique applied to
the spin s Heisenberg model. In a recent paper Kruczenski (hep-th/0311203)
suggested to solve the Heisenberg model by using of sigme model approach. In
this paper we generalize the solutions obtained by Kruczenski and comment on
the dual string theory. It turns out that our solutions are related to the so
called Neumann-Rosochatius integrable system. We comment on the spin chain
solutions and on the string/gauge theory correspondence.Comment: v.2 One reference added, typos corrected, 21 page
Hypothalamic FTO is associated with the regulation of energy intake not feeding reward
<p>Abstract</p> <p>Background</p> <p>Polymorphism in the FTO gene is strongly associated with obesity, but little is known about the molecular bases of this relationship. We investigated whether hypothalamic FTO is involved in energy-dependent overconsumption of food. We determined FTO mRNA levels in rodent models of short- and long-term intake of palatable fat or sugar, deprivation, diet-induced increase in body weight, baseline preference for fat versus sugar as well as in same-weight animals differing in the inherent propensity to eat calories especially upon availability of diverse diets, using quantitative PCR. FTO gene expression was also studied in organotypic hypothalamic cultures treated with anorexigenic amino acid, leucine. In situ hybridization (ISH) was utilized to study FTO signal in reward- and hunger-related sites, colocalization with anorexigenic oxytocin, and c-Fos immunoreactivity in FTO cells at initiation and termination of a meal.</p> <p>Results</p> <p>Deprivation upregulated FTO mRNA, while leucine downregulated it. Consumption of palatable diets or macronutrient preference did not affect FTO expression. However, the propensity to ingest more energy without an effect on body weight was associated with lower FTO mRNA levels. We found that 4-fold higher number of FTO cells displayed c-Fos at meal termination as compared to initiation in the paraventricular and arcuate nuclei of re-fed mice. Moreover, ISH showed that FTO is present mainly in hunger-related sites and it shows a high degree of colocalization with anorexigenic oxytocin.</p> <p>Conclusion</p> <p>We conclude that FTO mRNA is present mainly in sites related to hunger/satiation control; changes in hypothalamic FTO expression are associated with cues related to energy intake rather than feeding reward. In line with that, neurons involved in feeding termination express FTO. Interestingly, baseline FTO expression appears linked not only with energy intake but also energy metabolism.</p
Transverse momentum dependence of Bose-Einstein correlations in 200-A/GeV/c S + A collisions
The NA35 experiment has collected a high statistics set of momentum analyzed negative hadrons near and forward of midrapidity for central collisions of 200A GeV/c 32S+S, Cu, Ag, and Au. Using momentum space correlations to study the size of the source of particle production, the transverse source radii are found to decrease by ~40% at midrapidity and ~20% at forward rapidity while the longitudinal radius RL is found to decrease by ~50% as pT increases over the interval 50<pT<600 MeV/c. Calculations using a microscopic phase space approach (relativistic quantum molecular dynamics) reproduce the observed trends of the data. PACS: 25.75.+rAutoren: Th. Alber9, J. Bächler6, J. Bartke4, H. Bialkowska11, M. A. Bloomer3, R. Bock5, W. J. Braithwaite12, D. Brinkmann6, R. Brockmann5, P. Buncic5, P. Chan12, P. B. Cramer12, J. G. Cramer12, I. Derado9, V. Eckardt9, J. Eschke6, C. Favuzzi2, D. Ferenc6,13, B. Fleischmann5, P. Foka5, P. Freund9, M. Fuchs6, M. Gazdzicki6, E. Gladysz4, J. W. Harris3, M. Hoffman7, P. Jacobs3, S. Kabana6, K. Kadija9,13, J. Kosiec10, M. Kowalski4, A. Kühmichel6, M. Lahanas6, J. Y. Lee6, A. Ljubicic, Jr.13, S. Margetis3, J. T. Mitchell3, R. J. Morse3, E. Nappi2, G. Odyniec3, G. Paic13, A. D. Panagiotou1, A. Petridis1,9, A. Piper8, F. Posa2, A. M. Poskanzer3, F. Pühlhofer8, W. Rauch9, R. Renfordt6, W. Retyk10, D. Röhrich6, G. Roland6, H. Rothard6, K. Runge7, A. Sandoval5, J. Schambach3, N. Schmitz9, E. Schmoetten7, I. Schneider6, P. Seyboth9, J. Seyerlein9, E. Skrzypczak11, P. Spinelli2, P. Stefansky4, R. Stock6, H. Ströbele6, T. A. Trainor12, G. Vasileiadis1, M. Vassiliou1,9, D. Vranic13, S. Wenig6, and B. Wosiek4
Penalized Projection Estimator for Volatility Density
In this paper, we consider a stochastic volatility model ("Y" "t" , "V" "t" ), where the volatility (V "t" ) is a positive stationary Markov process. We assume that ("ln""V" "t" ) admits a stationary density "f" that we want to estimate. Only the price process "Y" "t" is observed at "n" discrete times with regular sampling interval Δ . We propose a non-parametric estimator for "f" obtained by a penalized projection method. Under mixing assumptions on ("V" "t" ), we derive bounds for the quadratic risk of the estimator. Assuming that Δ=Δ "n" tends to 0 while the number of observations and the length of the observation time tend to infinity, we discuss the rate of convergence of the risk. Examples of models included in this framework are given. Copyright 2006 Board of the Foundation of the Scandinavian Journal of Statistics..