Line and continuum radiative transfer modelling of AA Tau

We present photometric and spectroscopic models of the Classical T Tauri star AA Tau. Photometric and spectroscopic variability present in observations of AA Tau is attributed to a magnetically induced warp in the accretion disc, periodically occulting the photosphere on an 8.2--day timescale. Emission line profiles show signatures of both infall, attributed to magnetospherically accreting material, and outflow. Using the radiative transfer code TORUS, we have investigated the geometry and kinematics of AA Tau's circumstellar disc and outflow, which is modelled here as a disc wind. Photometric models have been used to constrain the aspect ratio of the disc, the offset angle of the magnetosphere dipole with respect to the stellar rotation axis, and the inner radius of the circumstellar disc. Spectroscopic models have been used to constrain the wind and magnetosphere temperatures, wind acceleration parameter, and mass loss rate. We find observations are best fitted by models with a mass accretion rate of $5\times10^{-9}$ M$_\odot$ yr$^{-1}$, a dipole offset of between $10^\circ$ and $20^\circ$, a magnetosphere that truncates the disc from 5.2 to 8.8 R$_\star$, a mass-loss-rate to accretion-rate ratio of ~ 0.1, a magnetosphere temperature of 8500 -- 9000 K, and a disc wind temperature of 8000 K.Comment: 22 pages, 32 figures, 4 tables. Accepted by MNRAS. V3: Corrected typ

The use of ultrasound for detecting particles suspended in lubricant and hydraulic fluids

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Fission-induced plasmas

The possibility of creating a plasma from fission fragments, and to utilize the energy of the particles to create population inversion that would lead to laser action is investigated. An investigation was made of various laser materials which could be used for nuclear-pumped lasing. The most likely candidate for a fissioning material in the gaseous form is uranium hexafluoride - UF6, and experiments were performed to investigate materials that would be compatible with it. One of the central problems in understanding a fission-induced plasma is to obtain a model of the electron behavior, and some preliminary calculations are presented. In particular, the rates of various processes are discussed. A simple intuitive model of the electron energy distribution function is also shown. The results were useful for considering a mathematical model of a nuclear-pumped laser. Next a theoretical model of a (3)He-Ar nuclear-pumped laser is presented. The theory showed good qualitative agreement with the experimental results

Computer simulation of plasma and N-body problems

The following FORTRAN language computer codes are presented: (1) efficient two- and three-dimensional central force potential solvers; (2) a three-dimensional simulator of an isolated galaxy which incorporates the potential solver; (3) a two-dimensional particle-in-cell simulator of the Jeans instability in an infinite self-gravitating compressible gas; and (4) a two-dimensional particle-in-cell simulator of a rotating self-gravitating compressible gaseous system of which rectangular coordinate and superior polar coordinate versions were written

Radial and rotational velocities of young brown dwarfs and very low-mass stars in the Upper Scorpius OB association and the rho Ophiuchi cloud core

We present the results of a radial velocity (RV) survey of 14 brown dwarfs (BDs) and very low-mass (VLM) stars in the Upper Scorpius OB association (UScoOB) and 3 BD candidates in the rho Ophiuchi dark cloud core. We obtained high-resolution echelle spectra at the Very Large Telescope using Ultraviolet and Visual Echelle Spectrograph (UVES) at two different epochs for each object, and measured the shifts in their RVs to identify candidates for binary/multiple systems in the sample. The average time separation of the RV measurements is 21.6d, and our survey is sensitive to the binaries with separation < 0.1 au. We found that 4 out of 17 objects (or 24^{+16}_{-13} per cent by fraction) show a significant RV change in 4-33d time scale, and are considered as binary/multiple `candidates.' We found no double-lined spectroscopic binaries in our sample, based on the shape of cross-correlation curves. The RV dispersion of the objects in UScoOB is found to be very similar to that of the BD and VLM stars in Chamaeleon I (Cha I). We also found the distribution of the mean rotational velocities (v sin i) of the UScoOB objects is similar to that of the Cha I, but the dispersion of v sin i is much larger than that of the Cha I objects.Comment: 10 pages, 5 figures, accepted for publication in MNRA

Indirect Detection of Forming Protoplanets via Chemical Asymmetries in Disks

We examine changes in the molecular abundances resulting from increased heating due to a self-luminous planetary companion embedded within a narrow circumstellar disk gap. Using 3D models that include stellar and planetary irradiation, we find that luminous young planets locally heat up the parent circumstellar disk by many tens of Kelvin, resulting in efficient thermal desorption of molecular species that are otherwise locally frozen out. Furthermore, the heating is deposited over large regions of the disk, $\pm5$ AU radially and spanning $\lesssim60^\circ$ azimuthally. From the 3D chemical models, we compute rotational line emission models and full ALMA simulations, and find that the chemical signatures of the young planet are detectable as chemical asymmetries in $\sim10h$ observations. HCN and its isotopologues are particularly clear tracers of planetary heating for the models considered here, and emission from multiple transitions of the same species is detectable, which encodes temperature information in addition to possible velocity information from the spectra itself. We find submillimeter molecular emission will be a useful tool to study gas giant planet formation in situ, especially beyond $R\gtrsim10$ AU.Comment: 14 pages, 14 figures, accepted for publication in Ap

The trajectory to diagnosis with pulmonary arterial hypertension: a qualitative study

Objectives To investigate the patient's experience of the trajectory to receiving a diagnosis of pulmonary arterial hypertension (PAH) and inform the provision of care for this patient group. Design Qualitative study using in-depth one-to-one interviews and pictorial representations. Data were analysed using thematic analysis. Setting Participants were interviewed in their own homes across England. Participants 30 patients with a diagnosis of pulmonary hypertension (18 participants were women, mean age 56 and range 26-80 02years and time since diagnosis ranged from a few months to more than 12 02years) participated. Results All participants, regardless of the time since diagnosis, vividly described the process from manifestation of symptoms to receiving a confirmed diagnosis. The authors present data using three major themes: (i) making sense of symptoms, (ii) process of elimination and (iii) being diagnosed with PAH. Making sense of symptoms represented an early period of perseverance 14people tried to carry-on as usual despite 18unexplained breathlessness 19. As time progressed, this period was punctuated by critical events that triggered seeking medical advice. Once medical contact had been made, patients described a period of 18elimination 19 and convoluted contact with the medical profession. Dyspnoea misdiagnosis was a key factor that delayed the PAH diagnosis. Diagnosis disclosure by some medical professionals was also viewed as lacking empathy. More positive experiences were relayed when the medical team disclosing the diagnosis acknowledged previous limitations. Conclusions A lack of awareness of this illness from both the sufferer themselves and the medical profession emerged as a central theme and led to prolonged periods of being misdiagnosed. The application of a diagnostic pathway for unexplained dyspnoea that alerts practitioners to rare conditions could expedite the process of correct diagnosis

Radiation-hydrodynamical simulations of massive star formation using Monte Carlo radiative transfer - I. Algorithms and numerical methods

Copyright © 2015 The Author Published by Oxford University Press on behalf of the Royal Astronomical SocietyWe present a set of new numerical methods that are relevant to calculating radiation pressure terms in hydrodynamics calculations, with a particular focus on massive star formation. The radiation force is determined from a Monte Carlo estimator and enables a complete treatment of the detailed microphysics, including polychromatic radiation and anisotropic scattering, in both the free-streaming and optically thick limits. Since the new method is computationally demanding we have developed two new methods that speed up the algorithm. The first is a photon packet splitting algorithm that enables efficient treatment of the Monte Carlo process in very optically thick regions. The second is a parallelization method that distributes the Monte Carlo workload over many instances of the hydrodynamic domain, resulting in excellent scaling of the radiation step. We also describe the implementation of a sink particle method that enables us to follow the accretion on to, and the growth of, the protostars. We detail the results of extensive testing and benchmarking of the new algorithms.Science & Technology Facilities Council (STFC