Model analysis of the world data on the pion transition form factor

We discuss the impact of recent Belle data on our description of the pion transition form factor based on the assumption that a perturbative formalism and a nonperturbative one can be matched in a physically acceptable manner at a certain hadronic scale $Q_{0}$. We discuss the implications of the different parameters of the model in comparing with world data and conclude that within experimental errors our description remains valid. Thus we can assert that the low $Q^2$ nonperturbative description together with an additional $1/Q^2$ term at the matching scale have a strong influence on the $Q^2$ behavior up to very high values of $Q^2$ .Comment: 6 pages and 3 figures. Contains a comparison with other models and additional reference

Logical Characterizations of Weighted Complexity Classes

Fagin’s seminal result characterizing NP in terms of existential second-order logic started the fruitful field of descriptive complexity theory. In recent years, there has been much interest in the investigation of quantitative (weighted) models of computations. In this paper, we start the study of descriptive complexity based on weighted Turing machines over arbitrary semirings. We provide machine-independent characterizations (over ordered structures) of the weighted complexity classes NP[S], FP[S], FPLOG[S], FPSPACE[S], and FPSPACEpoly[S] in terms of definability in suitable weighted logics for an arbitrary semiring S. In particular, we prove weighted versions of Fagin’s theorem (even for arbitrary structures, not necessarily ordered, provided that the semiring is idempotent and commutative), the Immerman–Vardi’s theorem (originally for P) and the Abiteboul–Vianu–Vardi’s theorem (originally for PSPACE). We also discuss a recent open problem proposed by Eiter and Kiesel. Recently, the above mentioned weighted complexity classes have been investigated in connection to classical counting complexity classes. Furthermore, several classical counting complexity classes have been characterized in terms of particular weighted logics over the semiring N of natural numbers. In this work, we cover several of these classes and obtain new results for others such as NPMV, ⊕P, or the collection of real-valued languages realized by polynomial-time real-valued nondeterministic Turing machines. Furthermore, our results apply to classes based on many other important semirings, such as the max-plus and the min-plus semirings over the natural numbers which correspond to the classical classes MaxP[O(log n)] and MinP[O(log n)], respectively. © Guillermo Badia, Manfred Droste, Carles Noguera, and Erik Paul

Polar surface engineering in ultra-thin MgO(111)/Ag(111) -- possibility of metal-insulator transition and magnetism

A recent report [Kiguchi {\it et al.}, Phys. Rev. B {\bf 68}, 115402 (2003)] that the (111) surface of 5 MgO layers grown epitaxially on Ag(111) becomes metallic to reduce the electric dipole moment raises a question of what will happen when we have fewer MgO layers. Here we have revealed, first experimentally with electron energy-loss spectroscopy, that MgO(111) remains metallic even when one-layer thick, and theoretically with the density functional theory that the metallization should depend on the nature of the substrate. We further show, with a spin-density functional calculation, that a ferromagnetic instability may be expected for thicker films.Comment: 5 pages, 7 figure

X-ray structure of the mature ectodomain of phogrin

Phogrin/IA-2β and ICA512/IA-2 are two paralogs receptor-type protein-tyrosine phosphatases (RPTP) that localize in secretory granules of various neuroendocrine cells. In pancreatic islet β-cells, they participate in the regulation of insulin secretion, ensuring proper granulogenesis, and β-cell proliferation. The role of their cytoplasmic tail has been partially unveiled, while that of their luminal region remains unclear. To advance the understanding of its structure-function relationship, the X-ray structure of the mature ectodomain of phogrin (ME phogrin) at pH 7.4 and 4.6 has been solved at 1.95- and 2.01-Å resolution, respectively. Similarly to the ME of ICA512, ME phogrin adopts a ferredoxin-like fold: a sheet of four antiparallel β-strands packed against two α-helices. Sequence conservation among vertebrates, plants and insects suggests that the structural similarity extends to all the receptor family. Crystallized ME phogrin is monomeric, in agreement with solution studies but in striking contrast with the behavior of homodimeric ME ICA512. The structural details that may cause the quaternary structure differences are analyzed. The results provide a basis for building models of the overall orientation and oligomerization state of the receptor in biological membranes

The pion transition form factor and the pion distribution amplitude

Recent BaBaR data on the pion transition form factor, whose Q^2 dependence is much steeper then predicted by asymptotic Quantum Chromodynamics (QCD), have caused a renewed interest in its theoretical description. We present here a formalism based on a model independent low energy description and a high energy description based on QCD, which match at a scale Q_0. The high energy description incorporates a flat pion distribution amplitude, phi(x)=1, at the matching scale Q_0 and QCD evolution from Q_0 to Q>Q_0. The flat pion distribution is connected, through soft pion theorems and chiral symmetry, to the pion valance parton distribution at the same low scale Q_0. The procedure leads to a good description of the data, and incorporating additional twist three effects, to an excellent description of the data.Comment: 11 pages, 5 postscript figures, uses epsfig.sty and 1 appendi

Absence of FGFR3–TACC3 rearrangement in hematological malignancies with numerical chromosomal alteration

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Laberintos del recuerdo: La representación de la memoria en ¡Olvídate de mí!

Resumen El artículo propone un estudio del filme ¡Olvídate de mí! como caso paradigmático de “película de memoria”. La cinta, dirigida por Michel Gondry y con guion de Charlie Kaufman, aborda la representación fílmica de la memoria personal de una manera lograda, en su doble condición de objeto y proceso. El análisis aborda en primer lugar cómo la memoria emerge en la película como eje temático de la representación fílmica. Después se analiza la estructura del relato, construida a partir distintas líneas narrativas que se entrecruzan constantemente y que provocan una evidente complejidad narratológica. Y, por último, se atiende a los tres rasgos más característicos de las películas de memoria: la subjetividad, la indiscernibilidad temporal y la performatividad. La forma en la que estos tres conceptos convergen en ¡Olvídate de mí! convierte este filme en un excelente ejemplo de las posibilidades a las que se abre la representación fílmica de la memoria personal. Abstract The article proposes a study of the film Eternal Sunshine of the Spotless Mind as a paradigmatic case of "memory film". The film, directed by Michel Gondry and written by Charlie Kaufman, addresses the filmic representation of personal memory in an accomplished way, in its double condition of object and process. The analysis first deals with how memory emerges in the film as its thematic axis. Then the structure of the story is analyzed, built with different narrative lines that constantly intersect and that cause an obvious narratological complexity. Finally, the three most characteristic features of memory films are addressed: subjectivity, temporal indiscernibility and performativity. The way in which these three features converge on Eternal Sunshine of the Spotless Mind makes this film an excellent example of the possibilities available in cinema for the representation of personal memory. Palabras clave: Memoria; película de memoria; narratología; subjetividad; indiscernibilidad temporal; performatividad. Keywords: Memory; memory film; narratology; subjectivity; temporary indiscernibility; performativity

Assessment of the Skill of Coupled Physical–Biogeochemical Models in the NW Mediterranean

Numerical modeling is a key tool to complement the current physical and biogeochemical observational datasets. It is essential for understanding the role of oceanographic processes on marine food webs and producing climate change projections of variables affecting key ecosystem functions. In this work, we evaluate the horizontalandverticalpatternsoffourstate-of-the-artcoupledphysical–biogeochemical models, three of them already published. Two of the models include data assimilation, physical and/or biological, and two do not. Simulations are compared to the most exhaustive dataset of in situ observations in the North Western Mediterranean, built ad hoc for this work, comprising gliders and conventional CTD surveys and complemented with satellite observations. The analyses are performed both in the whole domain and in four subregions (Catalan Shelf, Ebro Delta, Mallorca Channel, and Ibiza Channel), characterized by a priori divergent primary production dynamics and driving mechanisms. Overall, existing models offer a reasonable representation of physical processes including stratification, surface temperature, and surface currents, but it is shown that relatively small differences among them can lead to large differences in the response of biogeochemical variables. Our results show that all models are able to reproduce the main seasonal patterns of primary production both at the upper layer and at the deep chlorophyll maximum (DCM), as well as the differential behavior of the four subregions. However, there are significant discrepancies in the local variabilityoftheintensityofthewintermixing,phytoplanktonblooms,ortheintensityand depth of the DCM. All model runs show markedly contrasting patterns of interannual phytoplankton biomass in all four subregions. This lack of robustness should dissuade end users from using them to fill gaps in time series observations without assessing their appropriateness. Finally, we discuss the usability of these models for different applications in marine ecology, including fishery oceanography

Anaerobic digestion of whole-crop winter wheat silage for renewable energy production

With biogas production expanding across Europe in response to renewable energy incentives, a wider variety of crops need to be considered as feedstock. Maize, the most commonly used crop at present, is not ideal in cooler, wetter regions, where higher energy yields per hectare might be achieved with other cereals. Winter wheat is a possible candidate because, under these conditions, it has a good biomass yield, can be ensiled, and can be used as a whole crop material. The results showed that, when harvested at the medium milk stage, the specific methane yield was 0.32 m3 CH4 kg–1 volatile solids added, equal to 73% of the measured calorific value. Using crop yield values for the north of England, a net energy yield of 146–155 GJ ha–1 year–1 could be achieved after taking into account both direct and indirect energy consumption in cultivation, processing through anaerobic digestion, and spreading digestate back to the land. The process showed some limitations, however: the relatively low density of the substrate made it difficult to mix the digester, and there was a buildup of soluble chemical oxygen demand, which represented a loss in methane potential and may also have led to biofoaming. The high nitrogen content of the wheat initially caused problems, but these could be overcome by acclimatization. A combination of these factors is likely to limit the loading that can be applied to the digester when using winter wheat as a substrat