GRBs from unstable Poynting dominated outflows

Poynting flux driven outflows from magnetized rotators are a plausible explanation for gamma-ray burst engines. We suggest a new possibility for how such outflows might transfer energy into radiating particles. We argue that the Poynting flux drives non-linearly unstable large amplitude electromagnetic waves (LAEMW) which ``break'' at radii $r_t \sim 10^{14}$ cm where the MHD approximation becomes inapplicable. In the ``foaming'' (relativisticly reconnecting) regions formed during the wave breaks the random electric fields stochastically accelerate particles to ultrarelativistic energies which then radiate in turbulent electromagnetic fields. The typical energy of the emitted photons is a fraction of the fundamental Compton energy $\epsilon \sim f \hbar c/r_e$ with $f \sim 10^{-3}$ plus additional boosting due to the bulk motion of the medium. The emission properties are similar to synchrotron radiation, with a typical cooling time $\sim 10^{-4}$ sec. During the wave break, the plasma is also bulk accelerated in the outward radial direction and at larger radii can produce afterglows due to the interactions with external medium. The near equipartition fields required by afterglow models maybe due to magnetic field regeneration in the outflowing plasma (similarly to the field generation by LAEMW of laser-plasma interactions) and mixing with the upstream plasma.Comment: 15 pages, 1 figur

Ikaros represses and activates PU.1 cell-type-specifically through the multifunctional Sfpi1 URE and a myeloid specific enhancer

Generation of myeloid and lymphoid cells from progenitors involves dynamic changes in transcription factor expression and use, and disruption of hematopoietic transcription factor function and expression can contribute to leukemic transformation. PU.1 and Ikaros are pivotal factors whose expression and utilization are dynamically altered during hematopoietic development. Here, we demonstrate that expression of PU.1, encoded by the Sfpi1 gene, is divergently regulated by Ikaros in distinct cell type-specific contexts. Chromatin immune precipitation analysis and functional perturbations revealed that Ikaros can directly repress or activate Sfpi1 transcription via different PU.1 cis-elements, with PU.1 and Ikaros collaborating at myeloid-specific elements but not at other elements. Our results thus shed light on how PU.1 and Ikaros can act as lineage competency factors to facilitate both myeloid and lymphoid developmental programs

Dynamic Nonlinear X-waves for Femtosecond Pulse Propagation in Water

Recent experiments on femtosecond pulses in water displayed long distance propagation analogous to that reported in air. We verify this phenomena numerically and show that the propagation is dynamic as opposed to self-guided. Furthermore, we demonstrate that the propagation can be interpreted as due to dynamic nonlinear X-waves whose robustness and role in long distance propagation is shown to follow from the interplay between nonlinearity and chromatic dispersion.Comment: 4 page

Vector modulation instability induced by vacuum fluctuations in highly birefringent fibers in the anomalous dispersion regime

We report a detailed experimental study of vector modulation instability in highly birefringent optical fibers in the anomalous dispersion regime. We prove that the observed instability is mainly induced by vacuum fluctuations. The detuning of the spectral peaks agrees with linear perturbation analysis. The exact shape of the spectrum is well reproduced by numerical integration of stochastic nonlinear Schrodinger equations describing quantum propagation.Comment: 11 pages, 4 figures, to be published in Optics Letter

Conversion of CO2 by non- thermal inductively-coupled plasma catalysis

CO2 decomposition is a very strongly endothermic reaction where very high temperatures are required to thermally dissociate CO2. Radio frequency inductively-coupled plasma enables to selectively activate and dissociate CO2 at room temperature. Tuning the flow rate and the frequency of the radio frequency inductively-coupled plasma gives high yields of CO under mild conditions. Finally the discovery of a plasma catalytic effect has been demonstrated for CO2 dissociation that shows a significant increase of the CO yield by metallic meshes. The metallic meshes become catalysts under exposure to plasma to activate the recombination reaction of atomic O to yield O2, thereby reducing the reaction to convert CO back to CO2. Inductively-coupled hybrid plasma catalysis allows access to study and to utilize high CO2 conversion in a non-thermal plasma regime. This advance offers opportunities to investigate the possibility to use radio frequency inductively-coupled plasma to store superfluous renewable electricity into high-valuable CO in time where the price of renewable electricity is plunging.</p

Development and Application of a Functional Human Esophageal Mucosa Explant Platform to Eosinophilic Esophagitis.

There is an increasing prevalence of esophageal diseases but intact human tissue platforms to study esophageal function, disease mechanisms, and the interactions between cell types in situ are lacking. To address this, we utilized full thickness human donor esophagi to create and validate the ex vivo function of mucosa and smooth muscle (n = 25). Explanted tissue was tested for contractile responses to carbachol and histamine. We then treated ex vivo human esophageal mucosa with a cytokine cocktail to closely mimic the Th2 and inflammatory milieu of eosinophilic esophagitis (EoE) and assessed alterations in smooth muscle and extracellular matrix function and stiffening. We found that full thickness human esophagus as well as the individual layers of circular and longitudinal muscularis propria developed tension in response to carbachol ex vivo and that mucosa demonstrated squamous cell differentiation. Treatment of mucosa with Th2 and fibrotic cytokines recapitulated the majority of the clinical Eosinophilic Esophagitis Diagnostic Profile (EDP) on fluidic transcriptional microarray. Transforming growth factor-beta-1 (TGFβ1) increased gene expression of fibronectin, smooth muscle actin, and phospholamban (p &lt; 0.001). The EoE cocktail also increased stiffness and decreased mucosal compliance, akin to the functional alterations in EoE (p = 0.001). This work establishes a new, transcriptionally intact and physiologically functional human platform to model esophageal tissue responses in EoE

Probiotics: Finding the Right Regulatory Balance

Some products marketed as drugs should be excused from Phase I trials, but safety and efficacy claims for dietary supplements should be more tightly regulated

On the Properties of Two Pulses Propagating Simultaneously in Different Dispersion Regimes in a Nonlinear Planar Waveguide

Properties of two pulses propagating simultaneously in different dispersion regimes, anomalous and normal, in a Kerr-type planar waveguide are studied in the framework of the nonlinear Schroedinger equation. Catastrophic self-focusing and spatio-temporal splitting of the pulses is investigated. For the limiting case when the dispersive term of the pulse propagating in the normal dispersion regime can be neglected an indication of a possibility of a stable self-trapped propagation of both pulses is obtained.Comment: 18 pages (including 15 eps figures