Deep Chandra Observations of the Pulsar Wind Nebula Created by PSR B0355+54

We report on Chandra X-ray Observatory (CXO) observations of the pulsar wind nebula (PWN) associated with PSR B0355+54 (eight observations with a 395 ks total exposure, performed over an 8 month period). We investigated the spatial and spectral properties of the emission coincident with the pulsar, compact nebula (CN), and extended tail. We find that the CN morphology can be interpreted in a way that suggests a small angle between the pulsar spin axis and our line-of-sight, as inferred from the radio data. On larger scales, emission from the 7' (2 pc) tail is clearly seen. We also found hints of two faint extensions nearly orthogonal to the direction of the pulsar's proper motion. The spectrum extracted at the pulsar position can be described with an absorbed power-law + blackbody model. The nonthermal component can be attributed to magnetospheric emission, while the thermal component can be attributed to emission from either a hot spot (e.g., a polar cap) or the entire neutron star surface. Surprisingly, the spectrum of the tail shows only a slight hint of cooling with increasing distance from the pulsar. This implies either a low magnetic field with fast flow speed, or particle re-acceleration within the tail. We estimate physical properties of the PWN and compare the morphologies of the CN and the extended tail with those of other bow shock PWNe observed with long CXO exposures.Comment: 11 pages, 8 figure

Enhanced optical gain clamping for upstream packet based traffic on hybrid WDM/TDM-PON using fiber bragg grating

In this paper, we propose a method to mitigate the temporal power transients arising from Erbium doped fiber amplifiers (EDFAs) on packeted/bursty scenario. The technique, applicable on hybrid WDM/TDM-PON for extended reach, is based on a low power clamping provided by a distributed feedback (DFB) laser and a fiber Bragg grating (FBG). An mprovement in the data signal Q factor was achieved keeping the clamping control signal with a low power, accompanied by a maximum reduction in the gain excursion of 1.12 d

Gallot-Tanno Theorem for closed incomplete pseudo-Riemannian manifolds and applications

We extend the Gallot-Tanno Theorem to closed pseudo-Riemannian manifolds. It is done by showing that if the cone over a manifold admits a parallel symmetric $(0,2)-$tensor then it is Riemannian. Applications of this result to the existence of metrics with distinct Levi-Civita connections but having the same unparametrized geodesics and to the projective Obata conjecture are given. We also apply our result to show that the holonomy group of a closed $(O(p+1,q),S^{p,q})$-manifold does not preserve any nondegenerate splitting of $\R^{p+1,q}$.Comment: minor correction

Functionality of the GAL4/UAS system in Tribolium requires the use of endogenous core promoters

<p>Abstract</p> <p>Background</p> <p>The red flour beetle <it>Tribolium castaneum </it>has developed into an insect model system second only to <it>Drosophila</it>. Moreover, as a coleopteran it represents the most species-rich metazoan taxon which also includes many pest species. The genetic toolbox for <it>Tribolium </it>research has expanded in the past years but spatio-temporally controlled misexpression of genes has not been possible so far.</p> <p>Results</p> <p>Here we report the establishment of the GAL4/UAS binary expression system in <it>Tribolium castaneum</it>. Both GAL4Δ and GAL4VP16 driven by the endogenous heat shock inducible promoter of the <it>Tribolium hsp68 </it>gene are efficient in activating reporter gene expression under the control of the Upstream Activating Sequence (UAS). UAS driven ubiquitous tGFP fluorescence was observed in embryos within four hours after activation while <it>in-situ </it>hybridization against tGFP revealed expression already after two hours. The response is quick in relation to the duration of embryonic development in <it>Tribolium </it>- 72 hours with segmentation being completed after 24 hours - which makes the study of early embryonic processes possible using this system. By comparing the efficiency of constructs based on <it>Tribolium, Drosophila</it>, and artificial core promoters, respectively, we find that the use of endogenous core promoters is essential for high-level expression of transgenic constructs.</p> <p>Conclusions</p> <p>With the established GAL4/UAS binary expression system, ectopic misexpression approaches are now feasible in <it>Tribolium</it>. Our results support the contention that high-level transgene expression usually requires endogenous regulatory sequences, including endogenous core promoters in <it>Tribolium </it>and probably also other model systems.</p

Reverberation chambers a la carte: An overview of the different mode-stirring techniques

Reverberation chambers (RC), a name inspired in room acoustics, are also known in literature as reverberating, reverb, mode-stirred or mode-tuned chambers. In their basic form, they consist of a shielded metallic enclosure, forming a cavity resonator, together with some mode-stirring mechanism. The main goal of such stirring mechanism is to generate an amplitude-varying electromagnetic field that is ideally statistically uniform