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The significance of dust particles for the electron energy probability function (EEPF) and plasma oscillations is studied under varying magnetic field strength in a filamentary discharge hydrogen plasma. The experimental result shows that with an increase in dust density, the electron density decreases as a result of the charging of dust grains in the plasma background. A bi-Maxwellian EEPF is computed in both a pristine hydrogen plasma and a dust-containing plasma at different magnetic field strengths. We have observed that the increase in magnetic field decreases the lower energy electron population. The electron population of the lower energy range shows nearly identical results at magnetic field,
mT whereas the behaviour of the high-energy electron population becomes identical for a field strength
mT. From the observation, we have seen that the mid energy electron population slightly decreases and the high energy electron population slightly increases due to the presence of dust particles as compared to a pristine plasma. Further, very low energy electron population remains almost unchanged. With increase in dust density, the mid energy electron population further decreases whereas the high energy electron population slightly increases for different magnetic fields. But, no changes were observed for the very low energy electron population in the presence of dust particles. From the study of plasma oscillation, it is observed that the dominant frequency associated with the plasma oscillation is matched with the ion cyclotron frequency. The amplitude of the ion cyclotron frequency reduces with the increase of dust density which might be due to the decrease of plasma density.
Weed management is the major challenge to the success of boro rice (rice grown during Dec–Jan to May–Jun, also known as summer rice) in Southern Asia. Herbicide seems to be a cost effective and strategic tool from an agronomic view point to control weeds; however, herbicide application can potentially interfere with soil enzyme activity and microbial biomass carbon (MBC). A field study was conducted in 2012/13 and 2013/14 to evaluate the performance of sole and combined application of different pre-emergence herbicides in comparison to manual weeding in boro rice. Lowest weed density, biomass and highest weed control efficiency (~83%) were recorded with the pyrazosulfuron ethyl, causing higher grain yield (6.7 Mg ha−1 in 2012/13 and 4.5 Mg ha−1 in 2013/14) than treatments with chlorimuron + metsulfuron-methyl, bensulfuron methyl + pretilachlor, butachlor fb 2,4D, butachlor and cono-weeder. Among, the herbicidal treatments butachlor caused lower grain yield and higher weed density and biomass when compared to the others. Although grain yield was highest in weed-free treatments but net returns and (B:C) benefit cost ratio was highest for pyrazosulfuron ethyl due to high cost of hand weeding. After 15 days of herbicide application, lowest microbial biomass carbon was recorded with bensulfuron methyl + pretilachlor, whereas lower values of dehydrogenase and fluorescein diacetate activities were observed with the application of chlorimuron + metsulfuron-methyl at 15 days after herbicide application. Our results suggest that pyrazosulfuron ethyl is one broad-spectrum and economically effective herbicide for controlling weeds as an alternative to labour consuming hand weeding in boro rice cultivation.
EMU is a wide-field radio continuum survey planned for the new Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The primary goal of EMU is to make a deep (rms ∼ 10 μJy/beam) radio continuum survey of the entire Southern sky at 1.3 GHz, extending as far North as +30° declination, with a resolution of 10 arcsec. EMU is expected to detect and catalogue about 70 million galaxies, including typical star-forming galaxies up to z ∼ 1, powerful starbursts to even greater redshifts, and active galactic nuclei to the edge of the visible Universe. It will undoubtedly discover new classes of object. This paper defines the science goals and parameters of the survey, and describes the development of techniques necessary to maximise the science return from EMU.
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