A review of impulsive phase phenomena

A brief review is given of impulsive phase phenomena in support of the models used to compute the energies of the different components of the flares under study. The observational characteristics of the impulsive phase are discussed as well as the evidence for multi-thermal or non-thermal phenomena. The significance of time delays between hard X-rays and microwaves is discussed in terms of electron beams and Alfven waves, two-step acceleration, and secondary bursts at large distances from the primary source. Observations indicating the occurrence of chromospheric evaporation, coronal explosions, and thermal conduction fronts are reviewed briefly, followed by the gamma ray and neutron results. Finally, a preferred flare scenario and energy source are presented involving the interactions in a complex of magnetic loops with the consequent reconnection and electron acceleration

The flare kernel in the impulsive phase

The impulsive phase of a flare is characterized by impulsive bursts of X-ray and microwave radiation, related to impulsive footpoint heating up to 50 or 60 MK, by upward gas velocities (150 to 400 km/sec) and by a gradual increase of the flare's thermal energy content. These phenomena, as well as non-thermal effects, are all related to the impulsive energy injection into the flare. The available observations are also quantitatively consistent with a model in which energy is injected into the flare by beams of energetic electrons, causing ablation of chromospheric gas, followed by convective rise of gas. Thus, a hole is burned into the chromosphere; at the end of impulsive phase of an average flare the lower part of that hole is situated about 1800 km above the photosphere. H alpha and other optical and UV line emission is radiated by a thin layer (approx. 20 km) at the bottom of the flare kernel. The upward rising and outward streaming gas cools down by conduction in about 45 s. The non-thermal effects in the initial phase are due to curtailing of the energy distribution function by escape of energetic electrons. The single flux tube model of a flare does not fit with these observations; instead we propose the spaghetti-bundle model. Microwave and gamma-ray observations suggest the occurrence of dense flare knots of approx. 800 km diameter, and of high temperature. Future observations should concentrate on locating the microwave/gamma-ray sources, and on determining the kernel's fine structure and the related multi-loop structure of the flaring area

Signatures of middle aged, nearby pulsars in the cosmic ray lepton spectrum?

Recent data reported by the PAMELA and ATIC experiments, as well as cosmic ray lepton results from FERMI and H.E.S.S. collaborations sparked a series of papers explaining these results either by contributions of electron positron pairs to the local interstellar cosmic ray (CR) spectrum by dark matter (DM) or pulsars. Focusing here on pulsars, we argue that at the present, our knowledge about particle acceleration at pulsars as well as of the local Galactic CR propagation is still limited, i.e. the recent results for CR electrons and positrons constrain pulsar and propagation models. We will thus not present another attempt to explain the data by contributions of pulsars to the local CR lepton flux but rather to highlight the caveats in doing so.Comment: 6 pages, accepted for the publication in the proceedings of the ICATPP Conference on Cosmic Rays for Particle and Astroparticle Physics, Villa Olmo (Como), Oct. 201

New insights into the anti-inflammatory mechanisms of glucocorticoids : an emerging role for glucocorticoid-receptor-mediated transactivation

Glucocorticoids are anti-inflammatory drugs that are widely used for the treatment of numerous (autoimmune) inflammatory diseases. They exert their actions by binding to the glucocorticoid receptor (GR), a member of the nuclear receptor family of transcription factors. Upon ligand binding, the GR translocates to the nucleus, where it acts either as a homodimeric transcription factor that binds glucocorticoid response elements (GREs) in promoter regions of glucocorticoid (GC)-inducible genes, or as a monomeric protein that cooperates with other transcription factors to affect transcription. For decades, it has generally been believed that the undesirable side effects of GC therapy are induced by dimer-mediated transactivation, whereas its beneficial anti-inflammatory effects are mainly due to the monomer-mediated transrepressive actions of GR. Therefore, current research is focused on the development of dissociated compounds that exert only the GR monomer-dependent actions. However, many recent reports undermine this dogma by clearly showing that GR dimer-dependent transactivation is essential in the anti-inflammatory activities of GR. Many of these studies used GR(dim/dim) mutant mice, which show reduced GR dimerization and hence cannot control inflammation in several disease models. Here, we review the importance of GR dimers in the anti-inflammatory actions of GCs/GR, and hence we question the central dogma. We summarize the contribution of various GR dimer-inducible anti-inflammatory genes and question the use of selective GR agonists as therapeutic agents

J/ψJ/\psi production in Au+Au collisions at RHIC and the nuclear absorption

It is shown that a QCD based nuclear absorption model, with few parameters fixed to reproduce experimental $J/\psi$ yield in 200 GeV pp/pA and 450 GeV pA collisions can explain the preliminary PHENIX data on the centrality dependence of $J/\psi$ suppression in Cu+Cu collisions at RHIC energy, $\sqrt{s_{NN}}$=200 GeV. However, the model does not give satisfactory description to the preliminary PHENIX data on the centrality dependence of $J/\psi$ suppression in Au+Au collisions. The analysis suggest that in Au+Au collisions, $J/\psi$ are suppressed in a medium unlike the medium produced in SPS energy nuclear collisions or in RHIC energy Cu+Cu collisions.Comment: Revised version, published in Phys. Rev. C 74(2006)044907. PHENIX preliminary data on the centrality dependence of nuclear modification factor for $J/\psi$ in Cu+Cu and in Au+Au are analysed. 6 pages, 5 figure

The glucocorticoid receptor in inflammatory processes : transrepression is not enough

Glucocorticoids (GCs) are the most commonly used anti-inflammatory agents to treat inflammatory and immune diseases. However, steroid therapies are accompanied by severe side-effects during long-term treatment. The dogma that transrepression of genes, by tethering of the glucocorticoid receptor (GR) to DNA-bound pro-inflammatory transcription factors, is the main anti-inflammatory mechanism, is now challenged. Recent discoveries using conditional GR mutant mice and genomic approaches reveal that transactivation of anti-inflammatory acting genes is essential to suppress many inflammatory disease models. This novel view radically changes the concept to design selective acting GR ligands with a reduced side-effect profile

Prevent-Teach-Reinforce for Function-based Behavior Intervention Planning in Positive Behavior Support

The present study assessed the effectiveness of Prevent-Teach-Reinforce (P-T-R), an assessment-based model for students with behavior problems, using an A-B-A-B design with follow-up. Participants included three students in grades kindergarten, fourth, and fifth in a rural Midwestern school district. Results indicated that PTR was effective in reducing disruptive behaviors and increasing academic engaged time across all three participants. The results also indicated that the teacher participants were able to implement the behavior interventions with fidelity and with high levels of perceived social validity

Shadowing and Absorption Effects on J/psi Production in dA Collisions

We study medium modifications of J/psi production in cold nuclear media in deuterium-nucleus collisions. We discuss several parameterizations of the modifications of the parton densities in the nucleus, known as shadowing, an initial-state effect. We also include absorption of the produced J/psi by nucleons, a final-state effect. Both spatially homogeneous and inhomogeneous shadowing and absorption are considered. We use the number of binary nucleon-nucleon collisions as a centrality measure. Results are presented for d+Au collisions at sqrt{S_{NN}} = 200 GeV and for d+Pb collisions at sqrt{S_{NN}} = 6.2 TeV. To contrast the centrality dependence in pA and dA collisions, we also present pPb results at sqrt{S_{NN}} = 8.8 TeV.Comment: 22 pages, 11 figures, uses revte