Consistency of Bayesian procedures for variable selection

It has long been known that for the comparison of pairwise nested models, a decision based on the Bayes factor produces a consistent model selector (in the frequentist sense). Here we go beyond the usual consistency for nested pairwise models, and show that for a wide class of prior distributions, including intrinsic priors, the corresponding Bayesian procedure for variable selection in normal regression is consistent in the entire class of normal linear models. We find that the asymptotics of the Bayes factors for intrinsic priors are equivalent to those of the Schwarz (BIC) criterion. Also, recall that the Jeffreys--Lindley paradox refers to the well-known fact that a point null hypothesis on the normal mean parameter is always accepted when the variance of the conjugate prior goes to infinity. This implies that some limiting forms of proper prior distributions are not necessarily suitable for testing problems. Intrinsic priors are limits of proper prior distributions, and for finite sample sizes they have been proved to behave extremely well for variable selection in regression; a consequence of our results is that for intrinsic priors Lindley's paradox does not arise.Comment: Published in at http://dx.doi.org/10.1214/08-AOS606 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Surges and Si IV bursts in the solar atmosphere. Understanding IRIS and SST observations through RMHD experiments

Surges often appear as a result of the emergence of magnetized plasma from the solar interior. Traditionally, they are observed in chromospheric lines such as H$\alpha$ 6563 \AA and Ca II 8542 \AA. However, whether there is a response to the surge appearance and evolution in the Si IV lines or, in fact, in many other transition region lines has not been studied. In this paper we analyze a simultaneous episode of an H$\alpha$ surge and a Si IV burst that occurred on 2016 September 03 in active region AR12585. To that end, we use coordinated observations from the Interface Region Imaging Spectrograph (IRIS) and the Swedish 1-m Solar Telescope (SST). For the first time, we report emission of Si IV within the surge, finding profiles that are brighter and broader than the average. Furthermore, the brightest Si IV patches within the domain of the surge are located mainly near its footpoints. To understand the relation between the surges and the emission in transition region lines like Si IV, we have carried out 2.5D radiative MHD (RMHD) experiments of magnetic flux emergence episodes using the Bifrost code and including the non-equilibrium ionization of silicon. Through spectral synthesis we explain several features of the observations. We show that the presence of Si IV emission patches within the surge, their location near the surge footpoints and various observed spectral features are a natural consequence of the emergence of magnetized plasma from the interior to the atmosphere and the ensuing reconnection processes.Comment: 13 pages, 8 figures. The Astrophysical Journal (Accepted

Shedding light on the chromatin changes that modulate shade responses

Altres ajuts: COST-Action INDEPTH CA16212; Generalitat de Catalunya/CERCA programmePerception of vegetation proximity or plant shade informs of potential competition for resources by the neighboring vegetation. As vegetation proximity impacts on both light quantity and quality, perception of this cue by plant photoreceptors reprograms development to result in responses that allow plants to compete with the neighboring vegetation. Developmental reprogramming involves massive and rapid changes in gene expression, with the concerted action of photoreceptors and downstream transcription factors. Changes in gene expression can be modulated by epigenetic processes that alter chromatin compaction, influencing the accessibility and binding of transcription factors to regulatory elements in the DNA. However, little is known about the epigenetic regulation of plant responses to the proximity of other plants. In this manuscript, we review what is known about plant shade effects on chromatin changes at the cytological level, that is, changes in nuclear morphology and high order chromatin density. We address which are the specific histone post-transcriptional modifications that have been associated with changes in shade-regulated gene expression, such as histone acetylation and histone methylation. Furthermore, we explore the possible mechanisms that integrate shade signaling components and chromatin remodelers to settle epigenetic marks at specific loci. This review aims to be a starting point to understand how a specific environmental cue, plant shade, integrates with chromatin dynamics to implement the proper acclimation responses

Twisted flux tube emergence from the convection zone to the corona

3D numerical simulations of a horizontal magnetic flux tube emergence with different twist are carried out in a computational domain spanning the upper layers of the convection zone to the lower corona. We use the Oslo Staggered Code to solve the full MHD equations with non-grey and non-LTE radiative transfer and thermal conduction along the magnetic field lines. The emergence of the magnetic flux tube input at the bottom boundary into a weakly magnetized atmosphere is presented. The photospheric and chromospheric response is described with magnetograms, synthetic images and velocity field distributions. The emergence of a magnetic flux tube into such an atmosphere results in varied atmospheric responses. In the photosphere the granular size increases when the flux tube approaches from below. In the convective overshoot region some 200km above the photosphere adiabatic expansion produces cooling, darker regions with the structure of granulation cells. We also find collapsed granulation in the boundaries of the rising flux tube. Once the flux tube has crossed the photosphere, bright points related with concentrated magnetic field, vorticity, high vertical velocities and heating by compressed material are found at heights up to 500km above the photosphere. At greater heights in the magnetized chromosphere, the rising flux tube produces a cool, magnetized bubble that tends to expel the usual chromospheric oscillations. In addition the rising flux tube dramatically increases the chromospheric scale height, pushing the transition region and corona aside such that the chromosphere extends up to 6Mm above the photosphere. The emergence of magnetic flux tubes through the photosphere to the lower corona is a relatively slow process, taking of order 1 hour.Comment: 53 pages,79 figures, Submitted to Ap

Solar Flux Emergence Simulations

We simulate the rise through the upper convection zone and emergence through the solar surface of initially uniform, untwisted, horizontal magnetic flux with the same entropy as the non-magnetic plasma that is advected into a domain 48 Mm wide from from 20 Mm deep. The magnetic field is advected upward by the diverging upflows and pulled down in the downdrafts, which produces a hierarchy of loop like structures of increasingly smaller scale as the surface is approached. There are significant differences between the behavior of fields of 10 kG and 20 or 40 kG strength at 20 Mm depth. The 10 kG fields have little effect on the convective flows and show little magnetic buoyancy effects, reaching the surface in the typical fluid rise time from 20 Mm depth of 32 hours. 20 and 40 kG fields significantly modify the convective flows, leading to long thin cells of ascending fluid aligned with the magnetic field and their magnetic buoyancy makes them rise to the surface faster than the fluid rise time. The 20 kG field produces a large scale magnetic loop that as it emerges through the surface leads to the formation of a bipolar pore-like structure.Comment: Solar Physics (in press), 12 pages, 13 figur

Cooperation in costly-access environments

Understanding cooperative behavior in biological and social systems constitutes a scientific challenge, being the object of intense research over the past decades. Many mechanisms have been proposed to explain the presence and persistence of cooperation in those systems, showing that there is no unique explanation, as different scenarios have different possible driving forces. In this paper, we propose a model to study situations in which voluntary participation involves an access cost to the cooperative interaction, besides the cost associated with cooperation. The proposed costly-access prisoner’s dilemma (PD), a symmetric donation game with voluntary and costly participation, breaks the symmetry between abstainers and participants of the voluntary PD. A mean-field approach shows that, in well-mixed populations, the dynamic always leads the system to abstention. However, depending on the return parameter, numerical simulations in structured populations display an alternating behavior between mono-strategic, multi-stable, and coexistence phases. This behavior is fully explained through a theoretical analysis of the strategic motifs, the transitions being determined by the change in stability of those motifs

Late Protein Synthesis-Dependent Phases in CTA Long-Term Memory: BDNF Requirement

It has been proposed that long-term memory (LTM) persistence requires a late protein synthesis-dependent phase, even many hours after memory acquisition. Brain-derived neurotrophic factor (BDNF) is an essential protein synthesis product that has emerged as one of the most potent molecular mediators for long-term synaptic plasticity. Studies in the rat hippocampus have been shown that BDNF is capable to rescue the late-phase of long-term potentiation as well as the hippocampus-related LTM when protein synthesis was inhibited. Our previous studies on the insular cortex (IC), a region of the temporal cortex implicated in the acquisition and storage of conditioned taste aversion (CTA), have demonstrated that intracortical delivery of BDNF reverses the deficit in CTA memory caused by the inhibition of IC protein synthesis due to anisomycin administration during early acquisition. In this work, we first analyze whether CTA memory storage is protein synthesis-dependent in different time windows. We observed that CTA memory become sensible to protein synthesis inhibition 5 and 7 h after acquisition. Then, we explore the effect of BDNF delivery (2 μg/2 μl per side) in the IC during those late protein synthesis-dependent phases. Our results show that BDNF reverses the CTA memory deficit produced by protein synthesis inhibition in both phases. These findings support the notion that recurrent rounds of consolidation-like events take place in the neocortex for maintenance of CTA memory trace and that BDNF is an essential component of these processes

Development of type 2 diabetes mellitus thirty-one years after Billroth II in a patient asking for diabetes surgery

Introduction: Diabetes surgery in obese and slim patients seems to be a superior alternative to the current medical treatment. Gastric bypass is an alternative treat- ment for diabetes. Nevertheless, there are still doubts whether diabetes can recur if you gain weight or if the effects are maintained over time. Other questions refer to the type of surgery to make the bypass limb length or reservoir size for the resolution of the Diabetes Mellitus. Presentation of case: Male patient 69-year-old came to us in order to perform tailored One Anastomosis Gastric Bypass (BAGUA) to treat his type 2 diabetes mellitus and metabolic syndrome. He has a history of peptic ulcer treated with subtotal gastrectomy and Billroth II recons- truction 49 years ago. He currently is not obese and deve- loped diabetes 31 years after surgery. Discussion: Globally there are no reports of patients with normal BMI that after performing gastric bypass developed diabetes mellitus. There are cases where obese diabetic patients after gastric bypass improve or remits the T2DM, but it relapses due to insufficient weight loss or gain it. The patient with gastric bypass Billroth II type, should not developed diabetes. He is normal weight and not had weight gain that could be linked to the develop- ment of diabetes. Conclusions: The results generated by bariatric surgery are encouraging, but still do not clarify the precise way how surgery produces rapid improvement of systemic metabolism as in diabetes, but in our patient, the effect was quite different because the gastric bypass had no protective effect against diabetes

Characterization and improvement of rheological properties of sodium caseinate glycated with galactose, lactose and dextran

10 páginas, 7 figuras, 2 tablas.-- El pdf del artículo es la versión de autor.The aim of this work was to investigate the effect of non-enzymatic glycosylation with galactose, lactose, and 10 kDa dextran on the rheological properties of sodium caseinate. To promote the formation of covalent complexes, the reaction was done in solid state (aw = 0.67), pH 7.0 (0.1 M sodium phosphate buffer), and temperature set at 50 and 60 °C. The progress of Maillard reaction was indirectly traced by measuring the formation of the Amadori compound, through furosine (2-furoylmethyl-lysine) analysis, and brown polymers, and the resulting glycoconjugates were characterized by LC/ESI-MS and SEC. Results showed a higher reactivity of galactose than lactose and dextran to form the glycoconjugates, due to its smaller molecular weight. Glycation with galactose and lactose increased the viscosity of caseinate and also altered its flow characteristics from Newtonian to shear-thinning. Oscillatory testing showed a higher elastic modulus (G′) in glycoconjugates when compared to non-glycated caseinate, especially with galactose, where a gel-like behaviour was observed after long incubation times. Glycation with dextran did not produce substantial improvements in the rheological properties of caseinate, probably due to the limited extent of the reaction. Our results show that by controlling the rate and extent of the Maillard reaction is a technologically feasible operation to improve the viscosity and gelling properties of sodium caseinate-based ingredients.This work was supported by projects Consolider Ingenio 2010 FUN-C-FOOD CSD2007-00063 (Ministerio de Educación y Ciencia), ALIBIRD S-0505/AGR/000153 (Comunidad de Madrid) and Hatch project TEN00332 (University of Tennessee Institute of Agriculture). M. Corzo-Martínez thanks the CSIC for an I3P PhD-grant.Peer reviewe