Is Coherence Essential to Account for Pulsar Radio Emission?

Based on definitions, two joint-criteria, namely, the optical-thin constraint and the energy budget constraint, are proposed to judge whether the emission nature of radio pulsars is incoherent or obligatory to be coherent. We find that the widely accepted criterion, $kT_B \le \epsilon$, is not a rational criterion to describe the optical-thin condition, even for the simplest case. The energy budget constraint could be released by introducing a certain efficient radiation mechanism (e.g. the inverse Compton scattering, QL98) with emission power of a single particle as high as a critical value $P_{sing,c} to interpret high luminosities of pulsars in terms of incoherent emission mechanisms, if the optical-thin constraint could be released by certain mechanism as well. Coherence may not be an essential condition to account for pulsar radio emission

Estimation of shell radiation efficiency using a FEM-SmEdA algorithm

The radiation efficiencies of cylindrical and conical shells were investigated by using the statistical modal energy distribution analysis (SmEdA) and integrated FEM-SmEdA approaches. In cylindrical shell, three analytical algorithms were carried out, including SmEdA and two conventional approaches, i.e. the wave approach and the statistical energy analysis (SEA), and the results were compared with a former experimental one. SmEdA showed closest results with the experimental one, owing to its precise estimation of the coupling loss factors (CLF) which were further used to calculate the radiation efficiency. Furthermore, based on the analytical SmEdA, an integrated FEM-SmEdA algorithm is proposed. This hybrid method provided similar shell radiation efficiency for cylindrical shell, indicating its applicability in the analysis of complicated structures

Symbiotic nitrogen fixation by legumes in two Chinese grasslands estimated with the (15)N dilution technique

Symbiotic nitrogen (N) fixation by legumes was investigated using the (15)N dilution technique in two Chinese grasslands: one in the north-eastern Tibetan Plateau and the other in Inner Mongolia in China. A small amount (0.03 g N m(-2)) of (15)N labelled (NH(4))(2)SO(4) fertilizer was evenly distributed in two soils. One month after the (15)N addition, four legumes (Astragalus sp., Gueldenstaedtia diversifolia, Oxytropis ochrocephala and Trigonella ruthenica) in the alpine meadow and two legumes (Thermopsis lanceolata and Melissitus ruthenica) in the temperate steppe were collected. Several non-legume plant species were harvested as the reference. Above-ground biomass of legumes ranged from 8 to 24 g m(-2) in the alpine meadow and from 11 to 35 g m(-2) in the temperate steppe. The reference plants showed distinctly higher (15)N atom% excess than legumes (0.08% vs. 0.02% in the alpine meadow, 0.10% vs. 0.02% in the temperate steppe). The N derived from atmosphere (%Ndfa) ranged from 50 to 90% N in the alpine meadow, while it ranged from 85 to 92% in the temperate steppe. Based on the legume above-ground biomass, total symbiotic N(2)-fixation rate was estimated to be 1.00 g N m(-2) year(-1) in the alpine meadow and 1.15 g N m(-2) year(-1) in the temperate steppe. These N inputs by legumes can account for 9% of the gap between the N demand and the seasonal N release by mineralization in the alpine Kobresia grassland and 20% in the temperate Leymus grassland, respectively. Considering additional contribution of the root biomass, we suggest that biological N(2)-fixation by legumes plays an important role in the cycling of N in both Kobresia and Leymus grasslands on an annual scale