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

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&equals;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..

Productivity Gaps Among European Regions

How is the R&D-productivity link affected by the environment where firms locate? Are companies located with their registered offices in more R&D favorable environments better able to translate their R&D knowledge into productivity gains? Our paper tries to answer these questions analyzing - in the European context - if R&D performing companies cluster themselves in \u201chigher-order R&D regions\u201d, as the Economic Geography theories postulate, inducing a polarisation in terms of labour productivity in comparison with firms located in \u201clower-order R&D regions\u201d. The proposed microeconometric estimates are based on a unique longitudinal database of publicly-traded companies belonging to manufacturing and service sectors. The final unbalanced sample comprises 626 European companies for a total of 3,431observations, covering the period 1990-2008. Results show that European \u201chigher-order R&D regions\u201d not only invest more in R&D, but also achieve more in terms of productivity gains from their own research activities. Results also show that in the case of \u201clower-order R&D regions\u201d, physical capital stock is still playing a dominant role