No abstract

Qiao and his collaborators recently proposed an inverse Compton scattering model to explain radio emission from pulsars. In this paper, we investigate the polarization properties of pulsar emission in the model. First of all, using the lower frequency approximation, we derived the analytical amplitude of the inverse Compton scattered wave of a single electron in a strong magnetic Ðeld. We found that the outgoing radio emission of a single relativistic electron scattering o † the "" low-frequency waves ÏÏ produced by gap sparking should be linearly polarized and have no circular polarization at all. However, considering the coherency of the emission from a bunch of electrons, we found that the outgoing radiation from the inner part of the emission beam, i.e., that from the lower emission altitudes, preferentially has to have circular polarization. Computer simulations show that the polarization properties, such as the sense reversal of circular polarization near the pulse center, the S-shape of position angle swing of the linear polarization, and a strong linear polarization in conal components, can be reproduced in the ICS model.

Abstract. The shapes of pulse profiles, especially their variations with respect to observing frequencies, are very important to understand emission mechanisms of pulsars. However, no previous attempt has been made to interpret their complicated phenomenology. In this paper, we present theoretical simulations for the integrated pulse profiles and their frequency evolution within the framework of the inverse Compton scattering (ICS) model proposed by Qiao (1988) and Qiao & Lin (1998). Using the phase positions of the pulse components predicted by the "beam-frequency figure" of the ICS model, we present Gaussian fits to the multi-frequency pulse profiles for some pulsars. It is shown that the model can reproduce various types of the frequency evolution behaviors of pulse profiles observed.

Abstract. Global policies that regulate anthropogenic mercury emissions to the environment require quantitative and comprehensive source-receptor relationships for mercury emissions, transport and deposition among major continental regions. In this study, we use the GEOS-Chem global chemical transport model to establish source-receptor relationships among 11 major continental regions worldwide. Source-receptor relationships for surface mercury concentrations (SMC) show that some regions (e.g., East Asia, the Indian subcontinent, and Europe) should be responsible for their local surface Hg(II) and Hg(P) concentrations due to near-field transport and deposition contributions from their local anthropogenic emissions (up to 64 and 71 % for Hg(II) and Hg(P), respectively, over East Asia). We define the region of primary influence (RPI) and the region of secondary influence (RSI) to establish intercontinental influence patterns. Results indicate that East Asia is the SMC RPI for almost all other regions, while Europe, Russia, and the Indian subcontinent also make some contributions to SMC over some receptor regions because they are dominant RSI source regions. Source-receptor relationships for mercury deposition show that approximately 16 and 17 % of dry and wet deposition, respectively, over North America originate from East Asia, indicating that transpacific transport of East Asian emissions is the major foreign source of mercury deposition in North America. Europe, Southeast Asia, and the Indian subcontinent are also important mercury deposition sources for some receptor regions because they are the dominant RSIs. We also quantify seasonal variation on mercury deposition contributions over other regions from East Asia. Results show that mercury deposition (including dry and wet) contributions from East Asia over the Northern Hemisphere receptor regions (e.g., North America, Europe, Russia, the Middle East, and Middle Asia) vary seasonally, with the maximum values in summer and minimum values in winter. The opposite seasonal pattern occurs on mercury dry deposition contributions over Southeast Asia and the Indian subcontinent.

We report here a novel and simple method, without using any seeds or catalysts, to synthesize single-crystal germanium nanowires with tunable 10−115 nm diameters and of 10−20 μm length by the decomposition of a precursor [(CH3(CH2)7CHCH(CH2)7CH2NH2)4Ge]4+·(Cl-)4 (TOG) at 360 °C in trioctylamine. The diameter of Ge nanowires can be controlled by varying the concentration of TOG in solution.