The VATLY Radio Telescope

A small radio telescope (SRT) has been installed on the roof of the Hanoi astrophysics laboratory VATLY. It is equipped with a 2.6 m diameter mobile parabolic dish remotely controlled in elevation and azimuth and with super-heterodyne detection around the 21 cm hydrogen line. First results of observations of the Sun and of the centre of the Milky Way are presented. They demonstrate the high quality of the telescope performance and are used to evaluate lobe size, signal to noise ratios, anthropogenic interferences and measurement accuracies. Particular attention is given to the measurement of the pointing accuracy. The rich measurement programme that is now at hand is briefly sketched

Soybean yield, seed quality and thresh efficiency by mechanisation at different harvesting stages and postharvest ripening

This study determined the most appropriate and earliest soybean harvesting stage and the number of days of postharvest ripening with minimal effects on seed losses and quality when mechanical harvest and threshing were applied. Harvesting stages at four physiological maturities (60, 70, 80, and 90%) and various days of postharvest ripening treatment (1, 2, and 3 days) were applied for two soybean varieties DT12 and DT26. Harvesting at physiological maturity of 90% recorded the highest seed-shattering loss but the least seed damage (<5%) and highest seed quality, followed by a physiological maturity of 80%. There were no significant differences in seed yields between harvesting stages of 80 and 90% maturity. Harvesting soybeans at a physiological maturity of 60 and 70% resulted in no seed losses but a significant reduction in seed quality. To avoid adverse weather, an early harvest stage at a physiological maturity of 80% is suggested. Although postharvest ripening of soybeans for early harvest caused seed shattering losses (2-5%), it was necessary to ensure seed quality. These results indicate effective and practical methods for farmers at small households to use in early mechanical harvesting of soybeans

Observation of High Doppler Velocity Wings in the Nascent Wind of R Doradus

We study the morpho-kinematics in the nascent wind of AGB star R Doradus in the light of high Doppler velocity wings observed in the spectral lines of several species. We probe distances from the star between ∼10 and ∼100 au using ALMA observations of the emission of five different molecular lines. High Doppler velocity enhancements of the line emission are observed in the vicinity of the line of sight crossing the star, reminiscent of those recently interpreted as gas streams in the nascent wind of a similar AGB star, EP Aqr. They are present in both blue-shifted and red- shifted hemispheres but are not exactly back-to-back. They are accelerated at a typical rate of 0.7 km s$^{−1}$ au$^{−1}$ up to some 20 km s$^{−1}$. Important differences are observed between the emissions of different molecules. We exclude an effect of improper continuum subtraction. However, in contrast to EP Aqr, the line of sight plays no particular role in the R Dor morpho-kinematics, shedding doubt on the validity of a gas stream interpretation. We discuss possible interpretations in terms of stellar pulsations or of rotation of the gas in the environment of the star. We conclude that, in the state of current knowledge, no fully convincing picture of the physics governing the production of such high velocities, typically twice as large as the terminal velocity, can be reliably drawn. New high resolution analyses of observations of the nascent wind of oxygen-rich AGB stars are needed to clarify the issue

Simulation of proton-induced and iron-induced extensive air showers at extreme energies

The development of extensive air showers at extreme energies is studied using a simulation model much simpler and cruder, but also more transparent and flexible, than existing sophisticated codes. Evidence for its satisfactory performance is presented. As an illustration, shower elongation rates are evaluated in the $10^{18}$ to $10^{20}$ eV region and compared with recently published data. Lateral distribution functions of both muons and electrons/photons are also briefly discussed. Reliable results are obtained in the comparison between proton-induced and iron-induced showers.Comment: 22 pages, Preprint submitted to Astroparticle Physic

Response of Water Cherenkov Detectors to Small Signals: a Case Study

Detailed studies of the response of the VATLY water Cherenkovdetector, a replica of those used in the ground array of the PierreAuger Observatory, are presented with emphasis on the response to lowamplitude signals. The method used is to detect decay electrons frommuons stopping in the water volume. Results include properties of the detection process as well as of the atmospheric cosmic ray flux

Extensive Air Showers and the LPM Effect

A very simple model of thelongitudinal development of electromagnetic showers is presented,allowing for easy calculations at the highest energies where usualsimulation codes become impracticable because of the enormousmultiplicity of secondary shower particles. Shower profiles aredescribed in terms of a few parameters having Gaussianfluctuations. The model is applied to the impact of theLandau-Pomeranchuk-Migdal effect on the shower development, whichis found negligible in practical cases

The Vatly Radio Telescope: Performance Study

A detailed account of the performance of the VATLY radio telescope, operated in HaNoi on and near the 21 cm HI line, is given. Drift scans across the Sun are used to measure the dependence of the gain on frequency and power, revealing small nonlinearities at or below the percent level. Interferences associated with the electromagnetic pollution in the Ha Noi environment are described. The sensitivity of the instrument is discussed and demonstrated with the detection of the Crab. The reliability of the measurement of the spectral flux density is illustrated by comparing solar flux data measured in Ha Noi and at the Australian observatory of Learmonth

Mapping Atomic Hydrogen in the Disk of the Milky Way

The VATLY radio telescope has been used to draw the map of atomic hydrogen gas in the disk of the Milky Way. Evidence has been obtained for its differential rotation, its cloud and arm structure and the presence of a dark matter halo

Evaluation of Pseudomonas stutzeri AM1 and Pseudomonas oleovorans ST1.1 isolated from shrimp pond sediments as probiotics for whiteleg shrimp, Litopenaeus vannamei culture

This study aimed to isolate the probiotic potential of nitrifying bacterial strains and to evaluate their effects on water quality and growth performance of the whiteleg shrimp, Litopenaeus vannamei. Based on an initial screening of 100 isolates identified from sediment samples, 12 strains could remove nitrogen compounds and two strains (Pseudomonas stutzeri AM1 and P. oleovorans ST1.1) showed highly efficient nitrogen removal ability. Within 96 h, total ammonia nitrogen (TAN) removal efficiency in the two strains was 28.0-31.6% and 21.5-24.9%, respectively. The water addition of 103 CFUmL-1 of P. stutzeri AM1 (T1) and P. oleovorans ST1.1 (T2) effectively reduced TAN, nitrite, nitrate, and total sulfide and increased the survival rate and biomass of shrimp. However, no significant differences were found between the control (T0) and treatment groups (T1 and T2) in the final weight, weight gain and specific growth rate of shrimp. Overall, P. stutzeri AM1 (T1) and P. oleovorans ST1.1 used as water supplements improved water quality and the survival rate of whiteleg shrimp