681 research outputs found

    The 21 cm Signature of Shock Heated and Diffuse Cosmic String Wakes

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    The analysis of the 21 cm signature of cosmic string wakes is extended in several ways. First we consider the constraints on GμG\mu from the absorption signal of shock heated wakes laid down much later than matter radiation equality. Secondly we analyze the signal of diffuse wake, that is those wakes in which there is a baryon overdensity but which have not shock heated. Finally we compare the size of these signals compared to the expected thermal noise per pixel which dominates over the background cosmic gas brightness temperature and find that the cosmic string signal will exceed the thermal noise of an individual pixel in the Square Kilometre Array for string tensions Gμ>2.5×108G\mu > 2.5 \times 10^{-8}.Comment: 10 pages, 4 figures, Appendix added, version published in JCA

    A simple and efficient numerical scheme to integrate non-local potentials

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    As nuclear wave functions have to obey the Pauli principle, potentials issued from reaction theory or Hartree-Fock formalism using finite-range interactions contain a non-local part. Written in coordinate space representation, the Schrodinger equation becomes integro-differential, which is difficult to solve, contrary to the case of local potentials, where it is an ordinary differential equation. A simple and powerful method has been proposed several years ago, with the trivially equivalent potential method, where non-local potential is replaced by an equivalent local potential, which is state-dependent and has to be determined iteratively. Its main disadvantage, however, is the appearance of divergences in potentials if the wave functions have nodes, which is generally the case. We will show that divergences can be removed by a slight modification of the trivially equivalent potential method, leading to a very simple, stable and precise numerical technique to deal with non-local potentials. Examples will be provided with the calculation of the Hartree-Fock potential and associated wave functions of 16O using the finite-range N3LO realistic interaction.Comment: 8 pages, 2 figures, submitted to Eur. Phys. J.

    The 21 cm Signature of Cosmic String Wakes

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    We discuss the signature of a cosmic string wake in 21cm redshift surveys. Since 21cm surveys probe higher redshifts than optical large-scale structure surveys, the signatures of cosmic strings are more manifest in 21cm maps than they are in optical galaxy surveys. We find that, provided the tension of the cosmic string exceeds a critical value (which depends on both the redshift when the string wake is created and the redshift of observation), a cosmic string wake will generate an emission signal with a brightness temperature which approaches a limiting value which at a redshift of z+1=30z + 1 = 30 is close to 400 mK in the limit of large string tension. The signal will have a specific signature in position space: the excess 21cm radiation will be confined to a wedge-shaped region whose tip corresponds to the position of the string, whose planar dimensions are set by the planar dimensions of the string wake, and whose thickness (in redshift direction) depends on the string tension. For wakes created at zi+1=103z_i + 1 = 10^3, then at a redshift of z+1=30z + 1 = 30 the critical value of the string tension μ\mu is Gμ=6×107G \mu = 6 \times 10^{-7}, and it decreases linearly with redshift (for wakes created at the time of equal matter and radiation, the critical value is a factor of two lower at the same redshift). For smaller tensions, cosmic strings lead to an observable absorption signal with the same wedge geometry.Comment: 11 pages, 4 figures; a couple of comments added in the discussion sectio

    Effect of gamma radiation of 60Co on sunflower plants (Helianthus annuus L.) (Asteraceae), from irradiated achenes

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    In order to know the effect of 60Co gamma irradiation, in the sunflower crop, were irradiated achenes in the Transelektro LGI-01 in the Instituto Nacional de Investigaciones Nucleares. The data was evaluated under a completely randomized design, where the treatments were 0, 100, 200, 300, 400, 500, 600, 700, 800 and 900 Gy and four repetitions (10x4) = 40 experimental units. The response variables were: plant height, root length and volume, dry biomass. The results indicated that germination and sprouting decreased as the radiation increased, adjusting these to a quadratic model. Plant height, length, root volume and dry biomass decreased at high doses. From this investigation it was concluded, that doses of 100 and 200 Gy, have a stimulating effect on plant height and root length, being an important agent, to induce genetic variability in sunflower

    La influencia del «engagement» en las trayectorias formativas de los estudiantes de Bachillerato

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    The level of academic engagement of 307 second-year high school students is analyzed based on their previous results in the studies. For data collection, a questionnaire based on the Utrecht Work Engagement Scale for Students (Carmona-Halty, Schaufeli & Salanova, 2017) was designed. The analyzes carried out confirmed that the students who obtained the highest values on the engagement scale were those who had not repeated a year in their academic history, nor had they had difficulties in the prior learning process. The data obtained is relevant for educational practice and the development of preventive orientation programs.Se analiza el nivel de engagement académico de 307 estudiantes de segundo de Bachillerato en función de sus resultados previos en los estudios. Para la recogida de datos se diseñó un cuestionario basado en la Utrecht Work Engagement Scale for Students (Carmona-Halty, Schaufeli y Salanova, 2017). Los análisis realizados confirmaron que el alumnado que obtuvo valores más elevados en la escala de engagement eran los que en su trayectoria formativa no habían repetido curso, ni habían tenido dificultades en el proceso de aprendizaje previo. Los datos obtenidos son relevantes para la práctica educativa y el desarrollo de programas de orientación preventiva

    Lysophosphatidic Acid-Mediated GPR35 Signaling in CX3CR1<sup>+</sup> Macrophages Regulates Intestinal Homeostasis.

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    Single-nucleotide polymorphisms in the gene encoding G protein-coupled receptor 35 (GPR35) are associated with increased risk of inflammatory bowel disease. However, the mechanisms by which GPR35 modulates intestinal immune homeostasis remain undefined. Here, integrating zebrafish and mouse experimental models, we demonstrate that intestinal Gpr35 expression is microbiota dependent and enhanced upon inflammation. Moreover, murine GPR35 &lt;sup&gt;+&lt;/sup&gt; colonic macrophages are characterized by enhanced production of pro-inflammatory cytokines. We identify lysophosphatidic acid (LPA) as a potential endogenous ligand produced during intestinal inflammation, acting through GPR35 to induce tumor necrosis factor (Tnf) expression in macrophages. Mice lacking Gpr35 in CX3CR1 &lt;sup&gt;+&lt;/sup&gt; macrophages aggravate colitis when exposed to dextran sodium sulfate, which is associated with decreased transcript levels of the corticosterone-generating gene Cyp11b1 and macrophage-derived Tnf. Administration of TNF in these mice restores Cyp11b1 expression and intestinal corticosterone production and ameliorates DSS-induced colitis. Our findings indicate that LPA signals through GPR35 in CX3CR1 &lt;sup&gt;+&lt;/sup&gt; macrophages to maintain TNF-mediated intestinal homeostasis

    Analysis technique for exceptional points in open quantum systems and QPT analogy for the appearance of irreversibility

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    We propose an analysis technique for the exceptional points (EPs) occurring in the discrete spectrum of open quantum systems (OQS), using a semi-infinite chain coupled to an endpoint impurity as a prototype. We outline our method to locate the EPs in OQS, further obtaining an eigenvalue expansion in the vicinity of the EPs that gives rise to characteristic exponents. We also report the precise number of EPs occurring in an OQS with a continuum described by a quadratic dispersion curve. In particular, the number of EPs occurring in a bare discrete Hamiltonian of dimension nDn_\textrm{D} is given by nD(nD1)n_\textrm{D} (n_\textrm{D} - 1); if this discrete Hamiltonian is then coupled to continuum (or continua) to form an OQS, the interaction with the continuum generally produces an enlarged discrete solution space that includes a greater number of EPs, specifically 2nC(nC+nD)[2nC(nC+nD)1]2^{n_\textrm{C}} (n_\textrm{C} + n_\textrm{D}) [2^{n_\textrm{C}} (n_\textrm{C} + n_\textrm{D}) - 1] , in which nCn_\textrm{C} is the number of (non-degenerate) continua to which the discrete sector is attached. Finally, we offer a heuristic quantum phase transition analogy for the emergence of the resonance (giving rise to irreversibility via exponential decay) in which the decay width plays the role of the order parameter; the associated critical exponent is then determined by the above eigenvalue expansion.Comment: 16 pages, 7 figure

    Drivers of deforestation in the basin of the Usumacinta River: Inference on process from pattern analysis using generalised additive models.

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    Quantifying patterns of deforestation and linking these patterns to potentially influencing variables is a key component of modelling and projecting land use change. Statistical methods based on null hypothesis testing are only partially successful for interpreting deforestation in the context of the processes that have led to their formation. Simplifications of cause-consequence relationships that are difficult to support empirically may influence environment and development policies because they suggest simple solutions to complex problems. Deforestation is a complex process driven by multiple proximate and underlying factors and a range of scales. In this study we use a multivariate statistical analysis to provide contextual explanation for deforestation in the Usumacinta River Basin based on partial pattern matching. Our approach avoided testing trivial null hypotheses of lack of association and investigated the strength and form of the response to drivers. As not all factors involved in deforestation are easily mapped as GIS layers, analytical challenges arise due to lack of a one to one correspondence between mappable attributes and drivers. We avoided testing simple statistical hypotheses such as the detectability of a significant linear relationship between deforestation and proximity to roads or water. We developed a series of informative generalised additive models based on combinations of layers that corresponded to hypotheses regarding processes. The importance of the variables representing accessibility was emphasised by the analysis. We provide evidence that land tenure is a critical factor in shaping the decision to deforest and that direct beam insolation has an effect associated with fire frequency and intensity. The effect of winter insolation was found to have many applied implications for land management. The methodology was useful for interpreting the relative importance of sets of variables representing drivers of deforestation. It was an informative approach, thus allowing the construction of a comprehensive understanding of its causes
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