Gamma-Ray Burst Phenomenon as Collapse of QED Magnetized Vacuum Bubble: Analogy with Sonoluminescence

We consider the phenomenon of a gamma-ray burst as a nonlinear collapse of a magnetic cavity surrounding a neutron star with very strong magnetic field B = 10^15 - 10^16 G due to the process of the bubble shape instability in a resonant MHD field of the accreting plasma. The QED effect of vacuum polarizability by the strong magnetic field is taken into account. We develop an analogy with the phenomenon of sonoluminescence (SL) when the gas bubble is located in the surrounding liquid with a driven sound intensity. We show that this analogy between GRB and SL phenomena really exists.Comment: 14 pages, submitted to Natur

Magnetoelectric coupling in MnTiO3

We give general arguments that show that the linear magnetoelectric effect in antiferromagnetic materials gives rise to a magnetocapacitance anomaly—a divergence of the dielectric constant at the magnetic ordering temperature TN that appears in an applied magnetic field. The measurement of magnetodielectric response thus provides a definitive and experimentally accessiblemethod to recognize antiferromagnetic linear magnetoelectric materials, circumventing the experimental difficulties often involved in measuring electric polarization. We confirm this result experimentally using the example of MnTiO3, which we show to exhibit the linear magnetoelectric effect. No dielectric anomaly is observed at TN in the absence of an applied magnetic field. However, a sharp peak in the dielectric constant appears here when a magnetic field is applied along the c axis, reflecting a linear coupling of the polarization P with the antiferromagnetic order parameter L. In accordance with our theoretical analysis, the dielectric constant close to TN increases with the square of the magnetic field.

Radiative impact of mixing state of black carbon aerosol in Asian outflow

The radiative impact of the mixing state of black carbon (BC) aerosol is investigated in Asian outflow. The mixing state and size distribution of BC aerosol were measured with a ground-based single-particle soot photometer at a remote island (Fukue) in Japan in spring 2007. The mass concentration of BC in Asian continental air masses reached 0.5 μg m-3, with a mass median diameter of 200-220 nm. The median value of the shell/core diameter ratio increased to ∼1.6 in Asian continental and maritime air masses with a core diameter of 200 mn, while in free tropospheric and Japanese air masses it was 1.3-1.4. On the basis of theoretical calculations using the size distribution and mixing state of BC aerosol, scattering and absorption properties of PM1 aerosols were calculated under both dry and ambient conditions, considering the hygroscopic growth of aerosols. It was estimated that internal mixing enhanced the BC absorption by a factor of 1.5-1.6 compared to external mixing. The calculated absorption coefficient was 2-3 times higher in Asian continental air masses than in clean air. Coatings reduced the single-scattering albedo (SSA) of PM1 aerosol by 0.01 -0.02, which indicates the importance of the mixing state of BC aerosol in evaluating its radiative influence. The SSA was sensitive to changes in air mass type, with a value of ∼0.98 in Asian continental air masses and ∼0.95 in Japanese and free tropospheric air masses under ambient conditions. Copyright 2008 by the American Geophysical Union

Time lag between prompt optical emission and gamma-rays in GRBs

The prompt optical emission contemporaneous with the $\gamma$-rays from $\gamma$-ray bursts (GRBs) carries important information on the central engine and explosion mechanism. We study the time lag between prompt optical emission and $\gamma$-rays in GRB 990123 and GRB 041219a, which are the only two GRBs had been detected at optical wavelengths during the ascending burst phase. Assuming profiles of prompt optical light curves are the same as the prompt $\gamma$-rays, we simulate optical light curves with different time lags and compare them with the observed optical flux. Then the best fit time lag and its error are determined by chi-squared values. We find that time lags between prompt optical emission and $\gamma$-rays in GRB host galaxy rest-frames are consistent in the two GRBs, which is $5\sim7$ s for GRB 990123 and $1\sim5$ s for GRB 041219a. This result is consistent with a common origin of prompt optical and $\gamma$-ray emissions in the two GRBs. Based on synchrotron cooling model, we also derive the parameters for the two GRBs.Comment: 4 pages, 3 figures; accepted for publication in A&

Discrete cilia modelling with singularity distributions

We discuss in detail techniques for modelling flows due to finite and infinite arrays of beating cilia. An efficient technique, based on concepts from previous ‘singularity models’ is described, that is accurate in both near and far-fields. Cilia are modelled as curved slender ellipsoidal bodies by distributing Stokeslet and potential source dipole singularities along their centrelines, leading to an integral equation that can be solved using a simple and efficient discretisation. The computed velocity on the cilium surface is found to compare favourably with the boundary condition. We then present results for two topics of current interest in biology. 1) We present the first theoretical results showing the mechanism by which rotating embryonic nodal cilia produce a leftward flow by a ‘posterior tilt,’ and track particle motion in an array of three simulated nodal cilia. We find that, contrary to recent suggestions, there is no continuous layer of negative fluid transport close to the ciliated boundary. The mean leftward particle transport is found to be just over 1 μm/s, within experimentally measured ranges. We also discuss the accuracy of models that represent the action of cilia by steady rotlet arrays, in particular, confirming the importance of image systems in the boundary in establishing the far-field fluid transport. Future modelling may lead to understanding of the mechanisms by which morphogen gradients or mechanosensing cilia convert a directional flow to asymmetric gene expression. 2) We develop a more complex and detailed model of flow patterns in the periciliary layer of the airway surface liquid. Our results confirm that shear flow of the mucous layer drives a significant volume of periciliary liquid in the direction of mucus transport even during the recovery stroke of the cilia. Finally, we discuss the advantages and disadvantages of the singularity technique and outline future theoretical and experimental developments required to apply this technique to various other biological problems, particularly in the reproductive system

A λ = 1.3 Millimeter Aperture Synthesis Molecular Line Survey of Orion Kleinmann-Low

We present a 1".3 spatial resolution interferometric spectral line survey of the core of the Orion molecular cloud, obtained with the OVRO millimeter array. Covering 4 GHz bandwidth in total, the survey contains ~100 emission lines from 18 chemical species. The spatial distributions of a number of molecules point to source I near the IRc2 complex as the dominant energy source in the region but do not rule out the presence of additional lower luminosity objects. At arcsecond resolution, the offsets between dust emission and various molecular tracers suggest that the spectacular "hot core" emission in the Orion core arises via the heating and ablation of material from the surfaces of very high density clumps located ≳500 AU from source I and traced by the dust emission. We find no evidence for a strong internal heating source within the hot core condensation(s)

Photochemical production and loss rates of ozone at Sable Island, Nova Scotia during the North Atlantic Regional Experiment (NARE) 1993 summer intensive

Three weeks of summertime surface‐based chemical and meteorological observations at Sable Island, Nova Scotia during the North Atlantic Regional Experiment (NARE) 1993 summer intensive are used to study instantaneous photochemical production and loss rates of ozone by means of a numerical photochemical model. Results are most sensitive to the averaging scheme of data used to constrain the model and the ambient variability of the measurements. Model simulations driven by a time series of 5 min averaged data, most representative of the chemistry at the site, yield an average net photochemical ozone production of 3.6 ppbv/d. Estimates of net ozone production designed to filter out local sources, by using 1000–1400 LT median values of observations to drive the model and by excluding short‐lived hydrocarbons, give values ranging from 1 to 4 ppbv/d. These positive values of net ozone production within the marine boundary layer over Sable Island demonstrate the impact of polluted continental plumes on the background photochemistry of the region during the intensive. The dominant ambient variables controlling photochemical production and loss rates of ozone at the site during the measurement campaign appear to be levels of nitrogen oxides, ozone, nonmethane hydrocarbons, and solar intensity determined by cloud cover. The model partitioning of nitrogen oxides agrees for the most part with measurements, lending credence to calculated photochemical production and loss rates of ozone as well as inferred levels of peroxy radicals not measured at the site. Discrepancies, however, often occur during episodes of intermittent cloud cover, fog, and rain, suggesting the influence of cloud processes on air masses reaching the site