Invasión de la especie exótica Rugulopteryx okamurae en Andalucía: Estudios preliminares de la actividad fotosintética

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Solvable model of strings in a time-dependent plane-wave background

We investigate a string model defined by a special plane-wave metric ds^2 = 2dudv - l(u) x^2 du^2 + dx^2 with l(u) = k/u^2 and k=const > 0. This metric is a Penrose limit of some cosmological, Dp-brane and fundamental string backgrounds. Remarkably, in Rosen coordinates the metric has a ``null cosmology'' interpretation with flat spatial sections and scale factor which is a power of the light-cone time u. We show that: (i) This spacetime is a Lorentzian homogeneous space. In particular, like Minkowski space, it admits a boost isometry in u,v. (ii) It is an exact solution of string theory when supplemented by a u-dependent dilaton such that its exponent (i.e. effective string coupling) goes to zero at u=infinity and at the singularity u=0, reducing back-reaction effects. (iii) The classical string equations in this background become linear in the light-cone gauge and can be solved explicitly in terms of Bessel's functions; thus the string model can be directly quantized. This allows one to address the issue of singularity at the string-theory level. We examine the propagation of first-quantized point-particle and string modes in this time-dependent background. Using certain analytic continuation prescription we argue that string propagation through the singularity can be smooth.Comment: 58 pages, latex. v2: several references to related previous work adde

Graves' disease is associated with a defective expression of the immune regulatory molecule galectin-9 in antigen-presenting dendritic cells

Introduction Patients with autoimmune thyroid disease (AITD) show defects in their immune-regulatory mechanisms. Herein we assessed the expression and function of galectin-1 and galectin-9 (Gal-1, Gal-9) in dendritic cells (DCs) from patients with AITD. Materials and Methods Peripheral blood samples from 25 patients with Graves’ disease (GD), 11 Hashimoto’s thyroiditis (HT), and 24 healthy subjects were studied. Thyroid tissue samples from 44 patients with AITD and 22 patients with goiter were also analyzed. Expression and function of Gal-1 and Gal-9 was assessed by quantitative RT-PCR, immunofluorescence and flow cytometry. Results A diminished expression of Gal-9, but not of Gal-1, by peripheral blood DCs was observed in GD patients, mainly in those with Graves´ ophthalmopathy, and a significant negative association between disease severity and Gal-9 expression was detected. In addition, the mRNA levels of Gal-9 and its ligand TIM-3 were increased in thyroid tissue from AITD patients and its expression was associated with the levels of Th1/Th12/Th17 cytokines. Immunofluorescence studies proved that intrathyroidal Gal-9 expression was confined to DCs and macrophages. Finally, in vitro functional assays showed that exogenous Gal-9 had a suppressive effect on the release of Th1/Th2/Th17 cytokines by DC/lymphocyte autologous co-cultures from both AITD patients and healthy controls. Conclusions The altered pattern of expression of Gal-9 in peripheral blood DCs from GD patients, its correlation with disease severity as well as its ability to suppress cytokine release suggest that Gal-9 could be involved in the pathogenesis of AITDThis work was supported by grants from the Fondo de Investigaciones Sanitarias (FISS) PI10/ 02521 and S2010/BMD-2328 TIRONET (Comunidad de Madrid), Spain (to MM) and the Fondo de Cooperación Internacional en Ciencia y Tecnología (FONCICYT) 95395, European Union-México (to RGA

Exact solutions of closed string theory

We review explicitly known exact $D=4$ solutions with Minkowski signature in closed bosonic string theory. Classical string solutions with space-time interpretation are represented by conformal sigma models. Two large (intersecting) classes of solutions are described by gauged WZW models and `chiral null models' (models with conserved chiral null current). The latter class includes plane-wave type backgrounds (admitting a covariantly constant null Killing vector) and backgrounds with two null Killing vectors (e.g., fundamental string solution). $D>4$ chiral null models describe some exact $D=4$ solutions with electromagnetic fields, for example, extreme electric black holes, charged fundamental strings and their generalisations. In addition, there exists a class of conformal models representing axially symmetric stationary magnetic flux tube backgrounds (including, in particular, the dilatonic Melvin solution). In contrast to spherically symmetric chiral null models for which the corresponding conformal field theory is not known explicitly, the magnetic flux tube models (together with some non-semisimple WZW models) are among the first examples of solvable unitary conformal string models with non-trivial $D=4$ curved space-time interpretation. For these models one is able to express the quantum hamiltonian in terms of free fields and to find explicitly the physical spectrum and string partition function.Comment: 50 pages, harvma

Expression and trans-specific polymorphism of self-incompatibility RNases in Coffea (Rubiaceae)

Self-incompatibility (SI) is widespread in the angiosperms, but identifying the biochemical components of SI mechanisms has proven to be difficult in most lineages. Coffea (coffee; Rubiaceae) is a genus of old-world tropical understory trees in which the vast majority of diploid species utilize a mechanism of gametophytic self-incompatibility (GSI). The S-RNase GSI system was one of the first SI mechanisms to be biochemically characterized, and likely represents the ancestral Eudicot condition as evidenced by its functional characterization in both asterid (Solanaceae, Plantaginaceae) and rosid (Rosaceae) lineages. The S-RNase GSI mechanism employs the activity of class III RNase T2 proteins to terminate the growth of "self" pollen tubes. Here, we investigate the mechanism of Coffea GSI and specifically examine the potential for homology to S-RNase GSI by sequencing class III RNase T2 genes in populations of 14 African and Madagascan Coffea species and the closely related self-compatible species Psilanthus ebracteolatus. Phylogenetic analyses of these sequences aligned to a diverse sample of plant RNase T2 genes show that the Coffea genome contains at least three class III RNase T2 genes. Patterns of tissue-specific gene expression identify one of these RNase T2 genes as the putative Coffea S-RNase gene. We show that populations of SI Coffea are remarkably polymorphic for putative S-RNase alleles, and exhibit a persistent pattern of trans-specific polymorphism characteristic of all S-RNase genes previously isolated from GSI Eudicot lineages. We thus conclude that Coffea GSI is most likely homologous to the classic Eudicot S-RNase system, which was retained since the divergence of the Rubiaceae lineage from an ancient SI Eudicot ancestor, nearly 90 million years ago.United States National Science Foundation [0849186]; Society of Systematic Biologists; American Society of Plant Taxonomists; Duke University Graduate Schoolinfo:eu-repo/semantics/publishedVersio

Gauged WZW models and Non-abelian duality

We consider WZW models based on the non-semi-simple algebras that they were recently constructed as contractions of corresponding algebras for semi-simple groups. We give the explicit expression for the action of these models, as well as for a generalization of them, and discuss their general properties. Furthermore we consider gauged WZW models based on these non-semi-simple algebras and we show that there are equivalent to non-abelian duality transformations on WZW actions. We also show that a general non-abelian duality transformation can be thought of as a limiting case of the non-abelian quotient theory of the direct product of the original action and the WZW action for the symmetry gauge group $H$. In this action there is no Lagrange multiplier term that constrains the gauge field strength to vanish. A particular result is that the gauged WZW action for the coset $(G_k \otimes H_l)/H_{k+l}$ is equivalent, in the limit $l\to \infty$, to the dualized WZW action for $G_k$ with respect to the subgroup $H$.Comment: 35 pages, harvmac, THU-94/01 (a few minor changes in subsec. 4.1 are made, a 3rd App. and a Note are added

On Smooth Time-Dependent Orbifolds and Null Singularities

We study string theory on a non-singular time-dependent orbifold of flat space, known as the `null-brane'. The orbifold group, which involves only space-like identifications, is obtained by a combined action of a null Lorentz transformation and a constant shift in an extra direction. In the limit where the shift goes to zero, the geometry of this orbifold reproduces an orbifold with a light-like singularity, which was recently studied by Liu, Moore and Seiberg (hep-th/0204168). We find that the backreaction on the geometry due to a test particle can be made arbitrarily small, and that there are scattering processes which can be studied in the approximation of a constant background. We quantize strings on this orbifold and calculate the torus partition function. We construct a basis of states on the smooth orbifold whose tree level string interactions are nonsingular. We discuss the existence of physical modes in the singular orbifold which resolve the singularity. We also describe another way of making the singular orbifold smooth which involves a sandwich pp-wave.Comment: 24 pages, one figur

Red de reservas marinas para la Región de las Grandes Islas, Golfo de California: protocolo del proyecto de planeación y reporte de los talleres del equipo de planeación [Marine reserves network for the Midriff Islands Region, Gulf of California, Mexico: planning protocol and progress report to the WWF Mexico & Carlos Slim Foundation Alliance]

La Región de las Grandes Islas (RGI), localizada en el acuario del mundo, el Golfo de California, es reconocida a nivel mundial por su espectacular belleza, diversidad y productividad; en ocasiones se le ha denominada como "las Galápagos del Hemisferio Norte" (Figura 1). En sus 45 islas, incluyendo las dos más grandes de México, Tiburón e Isla Ángel de la Guarda, se han registrado más de 400 especies de plantas, anfibios, reptiles y mamíferos terrestres, algunas de ellas endémicas a una o varias de las islas. En algunas de estas islas, como Rasa y San Pedro Mártir, llegan a anidar cientos de miles de aves marinas. Alrededor de este gran archipiélago, se pueden observar hasta 23 especies de mamíferos marinos, incluyendo la súper agregación de cachalotes en la cuenca San Pedro Mártir. Así como también es un sitio usado por cinco especies de tortugas marinas para hibernar y alimentarse. [English] In collaboration with researchers, agencies and NGOs, we aim to guide the design and implementation of a network of marine reserves for Midriff Islands, Gulf of California, a marine conservation hotspot. The area is one of the most important fishing regions in Mexico and livelihoods of coastal communities are threatened by depletion of fish stocks and climate change. The project aims to develop a practical approach to design networks of marine reserves that consider ecological connectivity and the effects of climate change. The project is an example of interdisciplinary and collaborative applied research, including over 25 researchers and managers from NGOs (COBI, Pronatura), universities (James Cook University, The University of Queensland, Arizona State University, SCRIPPS, The University of Arizona), and national (Mexico’s Commissions for Protected Areas and Biodiversity) and international agencies (NOAA)

Distinct role of T helper Type 17 immune response for Graves\u27 hyperthyroidism in mice with different genetic backgrounds.

T helper type 17 (Th17) cells, a newly identified effector T-cell subset, have recently been shown to play a role in numerous autoimmune diseases, including iodine-induced autoimmune thyroiditis in non-obese diabetic (NOD)-H2(h4) mice, which had previously been thought Th1-dominant. We here studied the role of Th17 in Graves\u27 hyperthyroidism, another thyroid-specific autoimmune disease, in a mouse model. Two genetically distinct BALB/c and NOD-H2(h4) strains with intact or disrupted IL-17 genes (IL-17(+/+) or IL-17(-/-)) were immunized with adenovirus (Ad) expressing the thyrotropin receptor (TSHR) A-subunit (Ad-TSHR289). Both IL-17(+/+) and IL-17(-/-) mice developed anti-TSHR antibodies and hyperthyroidism at equally high frequencies on the BALB/c genetic background. In contrast, some IL-17(+/+), but none of IL-17(-/-), mice became hyperthyroid on the NOD-H2(h4) genetic background, indicating the crucial role of IL-17 for development of Graves\u27 hyperthyroidism in non-susceptible NOD-H2(h4), but not in susceptible BALB/c mice. In the T-cell recall assay, splenocytes and lymphocytes from the draining lymph nodes from either mouse strains, irrespective of IL-17 gene status, produced IFN-γ and IL-10 but not other cytokines including IL-17 in response to TSHR antigen. Thus, the functional significance of Th17 may not necessarily be predictable from cytokine expression patterns in splenocytes or inflammatory lesions. In conclusion, this is, to our knowledge, the first report showing that the role of Th17 cells for the pathogenesis of a certain autoimmune disease depends on the mouse genetic backgrounds