The role of newly born magnetars in gamma-ray burst X-ray afterglow emission: Energy injection and internal emission

Swift observations suggest that the central compact objects of some gamma-ray bursts (GRBs) could be newly born millisecond magnetars. Therefore, considering the spin evolution of the magnetars against r-mode instability, we investigate the role of magnetars in GRB X-ray afterglow emission. Besides modifying the conventional energy injection model, we pay particular attention to the internal X-ray afterglow emission, whose luminosity is assumed to track the magnetic dipole luminosity of the magnetars with a certain fraction. Following a comparison between the model and some selected observational samples, we suggest that some so-called canonical X-ray afterglows including the shallow decay, normal decay, and steeper-than-normal decay phases could be internally produced by the magnetars (possibly through some internal dissipations of the magnetar winds), while the (energized) external shocks are associated with another type of X-ray afterglows. If this is true, then from those internal X-ray afterglows we can further determine the magnetic field strengths and the initial spin periods of the corresponding magnetars. © 2010. The American Astronomical Society. All rights reserved.published_or_final_versio

Implications Of Fast Radio Bursts For Superconducting Cosmic Strings

postprin

The luminosity function of Swift long gamma-ray bursts

The accumulation of Swift observed gamma-ray bursts (GRBs) has gradually made it possible to directly derive a GRB luminosity function (LF) from the observational luminosity distribution. However, two complexities are involved: (i) the evolving connection between GRB rate and cosmic star formation rate; and (ii) observational selection effects due to telescope thresholds and redshift measurements. With a phenomenological investigation of these two complexities, we constrain and discriminate two popular competing LF models (i.e. the broken-power-law LF and the single-power-law LF with an exponential cut-off at low luminosities). As a result, we find that the broken-power-law LF may be more favoured by observations, with a break luminosity L b= 2.5 × 10 52ergs -1 and prior- and post-break indices ν 1= 1.72 and ν 2= 1.98. Regarding an extra evolution effect expressed by a factor (1 +z) δ, if the metallicity of GRB progenitors is lower than ~0.1Z ⊙ as expected by some collapsar models, then there may be no extra evolution effect other than the metallicity evolution (i.e. δ approaches zero). Alternatively, if we remove the theoretical metallicity requirement, then a relationship between the degenerate parameters δ and Z max can be found, very roughly, δ~ 2.4(Z max/Z ⊙- 0.06). This indicates that extra evolution could become necessary for relatively high metallicities. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.published_or_final_versio

Magnetic ordering at the edges of graphitic fragments: Magnetic tail interactions between the edge-localized states

To understand the formation mechanism of magnetic moments at the edges of graphitic fragments, we carry out first-principles density-functional calculations for the electronic and magnetic structures of graphitic fragments with various spin and geometric configurations. We find that interedge and interlayer interactions between the localized moments can be explained in terms of interactions between the magnetic tails of the edge-localized states. In addition, the dihydrogenated edge states as well as Fe ad-atoms at the edge are studied in regard to the magnetic order and proximity effects.open28621

High-redshift gamma-ray bursts: Observational signatures of superconducting cosmic strings?

The high-redshift gamma-ray bursts (GRBs), GRBs 080913 and 090423, challenge the conventional GRB progenitor models by their short durations, typical for short GRBs, and their high energy releases, typical for long GRBs. Meanwhile, the GRB rate inferred from high-redshift GRBs also remarkably exceeds the prediction of the collapsar model, with an ordinary star formation history. We show that all these contradictions could be eliminated naturally, if we ascribe some high-redshift GRBs to electromagnetic bursts of superconducting cosmic strings. High-redshift GRBs could become a reasonable way to test the superconducting cosmic string model because the event rate of cosmic string bursts increases rapidly with increasing redshifts, whereas the collapsar rate decreases. © 2010 The American Physical Society.published_or_final_versio

Content-aware photo collage using circle packing

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Modeling of the current density distribution under surface posterior-tibial-nerve electric stimulator

Stimulation of the posterior tibial nerve is commonly used in the measurement of somatosensory evoked potential (SEP). To improve the efficiency of stimulation, the potential field and current density distributions under the surface electrodes were modeled and simulated. In our model, three layers were assumed: (1) the air environment, (2) electrode and paste (3) human body (skin and soft tissues). The mirror method was used to analyze the potential field of point charge. Integration of the field and the area of the stimulus gave the potential field of one surface electric pole. The potential field distribution of the bipolar stimulator was obtained by superimposition of two unipolar fields. Finally, the current density distribution was calculated by Laplace equation. The analytical solution of the potential field was found and the numerical solution of the current density distribution calculated. The potential field and current density distributions were simulated by 2-D plot. From the model and simulation, the potential and current density distributions were not found to be uniform under transcutaneous stimulation electrode and the maximum current density is located under the poles. We recommend that bipolar stimulator should be applied axially along the stimulated nerve course.published_or_final_versio

Do contiguous multilevel pedicle screws offer added curve correction over alternate level screw strategy in AIS patients when curve flexibility is taken into account?

Concurrent Session 5A: Adolescent Idiopathic Scoliosis & Complications. Paper no. 97postprintThe 17th International Meeting on Advanced Spine Techniques (IMAST 2010), Toronto, Canada, 21-24 July 2010

Consumption of dried fruit of Crataegus pinnatifida (hawthorn) suppresses high-cholesterol diet-induced hypercholesterolemia in rats

Author name used in this publication: Mabel Yin-Chun YauAuthor name used in this publication: Peter Hoi-Fu Yu2009-2010 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe