Detection of C3O in the low-mass protostar Elias 18

We have performed new laboratory experiments which gave us the possibility to obtain an estimate of the amount of carbon chain oxides (namely C3O2, C2O, and C3O) formed after irradiation (with 200 keV protons) of pure CO ice, at 16 K. The analysis of laboratory data indicates that in dense molecular clouds, when high CO depletion occurs, an amount of carbon chain oxides as high as 2-3x10^-3 with respect to gas phase carbon monoxide can be formed after ion irradiation of icy grain mantles. Then we have searched for gas phase C2O and C3O towards ten low-mass young stellar objects. Among these we have detected the C3O line at 38486.891 MHz towards the low-mass protostar Elias 18. On the basis of the laboratory results we suggest that in dense molecular clouds gas phase carbon chain oxides are formed in the solid phase after cosmic ion irradiation of CO-rich icy mantles and released to the gas phase after desorption of icy mantles. We expect that the Atacama Large Millimeter Array (ALMA), thanks to its high sensitivity and resolution, will increase the number of carbon chain oxides detected in dense molecular clouds.Comment: 19 Pages, 5 figures, Accepted to Ap

A three-dimensional model for the radio emission of magnetic chemically peculiar stars

In this paper we present a three-dimensional numerical model for the radio emission of Magnetic Chemically Peculiar stars, on the hypothesis that energetic electrons emit by the gyrosynchrotron mechanism. For this class of radio stars, characterized by a mainly dipolar magnetic field whose axis is tilted with respect to the rotational axis, the geometry of the magnetosphere and its deformation due to the stellar rotation are determined. The radio emitting region is determined by the physical conditions of the magnetosphere and of the stellar wind. Free-free absorption by the thermal plasma trapped in the inner magnetosphere is also considered. Several free parameters are involved in the model, such as the size of the emitting region, the energy spectrum and the number density of the emitting electrons, and the characteristics of the plasma in the inner magnetosphere. By solving the equation of radiative transfer, along a path parallel to the line of sight, the radio brightness distribution and the total flux density as a function of stellar rotation are computed. As the model is applied to simulate the observed 5 GHz lightcurves of HD37479 and HD37017, several possible magnetosphere configurations are found. After simulations at other frequencies, in spite of the large number of parameters involved in the modeling, two solutions in the case of HD37479 and only one solution in the case of HD37017 match the observed spectral indices. The results of our simulations agree with the magnetically confined wind-shock model in a rotating magnetosphere. The X-ray emission from the inner magnetosphere is also computed, and found to be consistent with the observations.Comment: 15 pages, 10 figures, A&A in pres

Searching for OH maser emission towards the MIPSGAL compact Galactic bubbles

We conducted radio observations searching for OH 18-cm maser emission from a sample of 169 unclassified MIPSGAL compact Galactic bubbles. These sources are thought to be the circumstellar envelopes of different kinds of evolved stars. Our observations were aimed at shedding light on the nature of MIPSGAL bubbles, since their characterisation is a fundamental aid for the development of accurate physical models of stellar and Galaxy evolution. The maser emission is observatively linked to the last stages of the life of low- and intermediate-mass stars, which may constitute a significant fraction of the MIPSGAL bubbles. In particular OH masers are usually observed towards post-AGB stars. Our observations were performed with the Green Bank Telescope and, for each source, produced spectra around the four OH 18-cm transitions. The observations were compared with archive interferometer data in order to exclude possible contamination from nearby sources. The main result is that the OH maser emission is not a common feature among the MIPSGAL bubbles, with only one certain detection. We conclude that among the MIPSGAL bubbles the post-AGB stars could be very rare

3D-modelling of the stellar auroral radio emission

The electron cyclotron maser is the coherent emission process that gives rise to the radio lighthouse effect observed in the hot magnetic chemically peculiar star CU Virginis. It has also been proposed to explain the highly circularly polarized radio pulses observed on some ultra cool dwarfs, with spectral type earlier than M7. Such kind of coherent events resemble the auroral radio emission from the magnetized planets of the solar system. In this paper, we present a tridimensional model able to simulate the timing and profile of the pulses emitted by those stars characterized by a dipolar magnetic field by following the hypothesis of the laminar source model, used to explain the beaming of the terrestrial auroral kilometric radiation. This model proves to be a powerful tool to understand the auroral radio-emission phenomenon, allowing us to derive some general conclusions about the effects of the model's free parameters on the features of the coherent pulses, and to learn more about the detectability of such kind of pulsed radio emission.Comment: 11 pages, 8 figures; accepted for publication in MNRA

Research focusing on plant performance in constructed wetlands and agronomic application of treated wastewater – A set of experimental studies in Sicily (Italy)

Constructed wetlands are sustainable technologies for the treatment of wastewater. These biological systems have been widely studied throughout the world for more than 30 years; however, most studies have focused on the effects of design and engineering on pollutant removal from wastewater. Undoubtedly, agro-technical aspects have been given too little consideration by research. This paper reports the main results of a set of experiments carried out on two pilot horizontal subsurface flow systems in Sicily (Italy). Festuca, Lolium and Pennisetum spp. in combination and three emergent macrophytes–Arundo donax L., Cyperus alternifolius L. and Typha latifolia L.–alone, were assessed. The aim of the study was to demonstrate that, under predetermined hydraulic and design conditions, the choice of plant species and the management of the vegetation can significantly affect the pollutant removal performance of constructed wetlands. In addition, wastewater (after treatment) can also be used for agricultural purposes leading to increased sustainability in agricultural systems. Arundo and Typha-planted units performed better than Cyperus-planted units in terms of chemical, physical and microbiological contaminant removal. All the species adapted extremely well to wetland conditions. Polyculture systems were found to be more efficient than monocultures in the removal of dissolved organic compounds. The reuse of treated wastewater for the irrigation of open fields and horticultural crops led to significant savings in the use of freshwater and fertilizers. The results of physical-energy characterization of A. donax above-ground plant residues and pellets highlighted the fact that a constructed wetland could also be a potential source of bioenergy

Numerical and Experimental Analysis of Transient Flow in Roots Blower

The performance of rotary positive displacement machines highly depends on the operational clearances. It is widely believed that computational fluid dynamics (CFD) can help understanding internal leakage flows. Developments of grid generating tools for analysis of leakage flows by CFD in rotary positive displacement machines have not yet been fully validated. Roots blower is a good representative of positive displacement machines and as such is convenient for optical access in order to analyse internal flows. The experimental investigation of flow in optical roots blower by phase-locked PIV (Particle Image Velocimetry) performed in the Centre for Compressor Technology at City, University of London provided the velocity field suitable for validation of the simulation model. This paper shows the results of the three-dimensional CFD transient simulation model of a Roots blower with the dynamic numerical grids generated by SCORG and flow solution solved in ANSYS CFX flow solver to obtain internal flow patterns. The velocity fields obtained by simulation agree qualitatively with the experimental results and show the correct main flow features in the working chamber. There are some differences in the velocity magnitude and vortex distribution. The flow field in roots blower is highly turbulent and three-dimensional. The axial clearances should be included, and the axial grids should be refined in the simulation method. The paper outlines some directions for future simulation and experimental work. The work described in this paper is a part of the large project set to evaluate characteristics of the internal flow in rotary positive displacement machines and to characterize leakage flow

Experimental Investigation of the Transient Flow in Roots Blower

Rotary positive displacement machines are common method to pump flow in various process industries. Their performance highly depends on the operational clearances. It is widely believed that computational fluid dynamics (CFD) can help understanding and reducing internal leakage flows. However, Developments of grid generating tools for use of CFD in rotary positive displacement machines have not yet been fully validated. Thereby arising a need to validate these models that help in better understanding of the leakage flows. Roots blower is a good representative of positive displacement machines and as such is convenient for optical access to analyse flows in in such machines. This paper describes the setup of the experimental test rig with the optical Roots blower in the Centre for Compressor Technology at City, University of London and the first results obtained using three different flow visualization methods. These are namely i) the high-speed camera (HC), ii) the continuous time resolved PIV (CPIV) and iii) the instantaneous PIV obtained with double pulse PIV laser and double shutter camera (IPIV). Test results from these three tests are compared and discussed in the paper. The CPIV test shows the movement of the vortex and the general shape of the flow field clearly but is not sufficient to calculate velocity vectors of high-velocity particles due to the limitation of the laser and camera. The IPIV test can produce quantitative velocity vector images of the internal flow but needs improvement to look into the leakage flow. The work described in this paper is a part of the large project set to evaluate characteristics of the internal flow in rotary positive displacement machines and to characterize leakage flows. The objective is to enable further improvements in 3D CFD analysis of leakage flows in rotary positive displacement machines and ultimately lead to the improvement in the performance of rotary positive displacement machines

Pengembangan Kontrol Alat Elektronik pada SMK XYZ

Tujuan dari penulisan skripsi adalah untuk menghasilakan karya nyata mengotrol suatu alat elektronik secara sistem otomatis agar mempermudah manusia dalam melakukan pekerjaanya dalam keadaan jarak jauh. Metode Penelitian yang digunakan adalah dengan metode pengumpulan data dan pengembangan sistem (Prototype). Dimana penulis mengumpulkan data yang dibutuhkan serta mendengarkan permintaan pengguna kemudian membangun Prototype itu.Hasil yang dicapai adalah menyalakan dan mematikan suatu alat elektronik dengan menggunakan Visual Basic 2010 yang dihubungkan dengan Device Controller. Dengan ini mempermudah kerja manusia dalam mengontrol alat elektronik tersebut pada jarak jauh.Kesimpulan bahwa Pengembangan Kontrol Alat Elektronik Menggunakan Visual Basic 2010 pada SMK XYZ jarak jauh menggunakan Visual Basic 2010 dapat di hubungkan dengan Device Controller yang terhubung dengan alat elektronik dan dapat mengontrol secara jarak jauh