A survey for redshifted molecular and atomic absorption lines - II. Associated HI, OH and millimetre lines in the z >~ 3 Parkes quarter-Jansky flat-spectrum sample

We present the results of a z>2.9 survey for HI 21-cm and molecular absorption in the hosts of radio quasars using the GMRT and the Tidbinbilla 70-m telescope. Previously published searches, which are overwhelmingly at redshifts of z<1, exhibit a 42% detection rate (31 out of 73 sources), and the inclusion of our survey yields a 17% detection rate (2 out of 12 sources) at z>2.5. We therefore believe that our high redshift selection is responsible for our exclusive non-detections, and find that at ultra-violet luminosities of >10e23 W/Hz, 21-cm absorption has never been detected. We also find this to not only apply to our targets, but also those at low redshift exhibiting similar luminosities, giving zero detections out of a total of 16 sources over z=0.24 to 3.8. This is in contrast to the < 10e23 W/Hz sources where there is a near 50% detection rate of 21-cm absorption. The mix of 21-cm detections and non-detections is currently attributed to orientation effects, where according to unified schemes of active galactic nuclei, 21-cm absorption is more likely to occur in sources designated as radio galaxies (type-2 objects, where the nucleus is viewed through dense obscuring circumnuclear gas) than in quasars(type-1 objects, where we have a direct view to the nucleus). However, due to the exclusively high ultra-violet luminosities of our targets it is not clear whether orientation effects alone can wholly account for the distribution, although there exists the possibility that the large luminosities are indicative of a changing demographic of galaxy types. We also find that below luminosities of ~10e23 W/Hz, both type-1 and type-2 objects have a 50% likelihood of exhibiting 21-cm absorption.Comment: 21 pages, accepted by MNRA

Researching Bradford: A review of social research on Bradford District

A synthesis of findings from social research on the District of Bradford. This report synthesises the findings from a wide range of social research undertaken on the District of Bradford, primarily between 1995 and 2005. The researchers reviewed almost 200 pieces of work. The key results are summarised under thematic headings: - The social, economic and institutional context - Community cohesion - Housing, neighbourhoods and regeneration - Business and enterprise - Health, disability and social care - Children and young people - Education, skills and the labour market - Crime and community safety It also identifies a future research agenda. The main purpose of the review was to provide the Joseph Rowntree Foundation and local organisations in Bradford with a firm basis upon which to build future work in the District

The molecular environment of massive star forming cores associated with Class II methanol maser emission

Methanol maser emission has proven to be an excellent signpost of regions undergoing massive star formation (MSF). To investigate their role as an evolutionary tracer, we have recently completed a large observing program with the ATCA to derive the dynamical and physical properties of molecular/ionised gas towards a sample of MSF regions traced by 6.7 GHz methanol maser emission. We find that the molecular gas in many of these regions breaks up into multiple sub-clumps which we separate into groups based on their association with/without methanol maser and cm continuum emission. The temperature and dynamic state of the molecular gas is markedly different between the groups. Based on these differences, we attempt to assess the evolutionary state of the cores in the groups and thus investigate the role of class II methanol masers as a tracer of MSF.Comment: 5 pages, 1 figure, IAU Symposium 242 Conference Proceeding

Evaluation of different internal standards for precious metals quantification

The current study involved the evaluation of five different internal standards (Sc, Co, Y, In and La) as well as normal external or direct calibration methods in the simultaneous quantification of all six platinum group metals (PGMs) and gold (precious metals). The use of Sc as internal standard in the quantitative determination of precious metals in a liquid reference material (RM) and the geological Pyroxenite CRM was shown to yield excellent recoveries (&gt; 99%) compared to the other metals used as internal standard in this study and the direct calibration method (&gt; 91 %).Os recovered only 89% of the expected metal content. The evaluation of different proposed models (wavelength combinations, ionization and/or excitation energy) did not succeed in identifying or discriminating between the unsuccessful and successful internal standards. The robustness of the Sc internal standard addition method was evaluated with the variation in solution matrix (addition of HCl and NaCl). The analytical method (total metal recovery) proved to be very sensitive to elevated unmatched HCl matrix levels (above 1.0 mL of HCl (32% v/v) added) and Na+ addition larger than 4 ppm sodium using ICP-OES. KEY WORDS: Internal standard, Scandium, Precious metals, Spectrometric techniques, ICP-OES Bull. Chem. Soc. Ethiop. 2016, 30(1), 55-70.DOI: http://dx.doi.org/10.4314/bcse.v30i1.

Resonant Metalenses for Breaking the Diffraction Barrier

We introduce the resonant metalens, a cluster of coupled subwavelength resonators. Dispersion allows the conversion of subwavelength wavefields into temporal signatures while the Purcell effect permits an efficient radiation of this information in the far-field. The study of an array of resonant wires using microwaves provides a physical understanding of the underlying mechanism. We experimentally demonstrate imaging and focusing from the far-field with resolutions far below the diffraction limit. This concept is realizable at any frequency where subwavelength resonators can be designed.Comment: 4 pages, 3 figure

Interacting Large-Scale Magnetic Fields and Ionised Gas in the W50/SS433 System

The W50/SS433 system is an unusual Galactic outflow-driven object of debatable origin. We have used the Australia Telescope Compact Array (ATCA) to observe a new 198 pointing mosaic, covering $3^\circ \times 2^\circ$, and present the highest-sensitivity full-Stokes data of W50 to date using wide-field, wide-band imaging over a 2 GHz bandwidth centred at 2.1 GHz. We also present a complementary H$\alpha$ mosaic created using the Isaac Newton Telescope Photometric H$\alpha$ Survey of the Northern Galactic Plane (IPHAS). The magnetic structure of W50 is found to be consistent with the prevailing hypothesis that the nebula is a reanimated shell-like supernova remnant (SNR), that has been re-energised by the jets from SS433. We observe strong depolarization effects that correlate with diffuse H$\alpha$ emission, likely due to spatially-varying Faraday rotation measure (RM) fluctuations of $\ge48$ to 61 rad m$^{-2}$ on scales $\le4.5$ to 6 pc. We also report the discovery of numerous, faint, H$\alpha$ filaments that are unambiguously associated with the central region of W50. These thin filaments are suggestive of a SNR's shock emission, and almost all have a radio counterpart. Furthermore, an RM-gradient is detected across the central region of W50, which we interpret as a loop magnetic field with a symmetry axis offset by $\approx90^{\circ}$ to the east-west jet-alignment axis, and implying that the evolutionary processes of both the jets and the SNR must be coupled. A separate RM-gradient is associated with the termination shock in the Eastern ear, which we interpret as a ring-like field located where the shock of the jet interacts with the circumstellar medium. Future optical observations will be able to use the new H$\alpha$ filaments to probe the kinematics of the shell of W50, potentially allowing for a definitive experiment on W50's formation history.Comment: Submitted to MNRA

Resonance between Noise and Delay

We propose here a stochastic binary element whose transition rate depends on its state at a fixed interval in the past. With this delayed stochastic transition this is one of the simplest dynamical models under the influence of ``noise'' and ``delay''. We demonstrate numerically and analytically that we can observe resonant phenomena between the oscillatory behavior due to noise and that due to delay.Comment: 4 pages, 5 figures, submitted to Phys.Rev.Lett Expanded and Added Reference

Carbon­yl(N-nitroso-N-oxido-1-naphtylamine-κ2 O,O′)(triphenyl­phosphine-κP)rhodium(I) acetone solvate

The title compound, [Rh(C10H7N2O2)(C18H15P)(CO)]·(CH3)2CO, is the second structural report of a metal complex formed with the O,O′-C10H7N2O2 (neocupferrate) ligand. In the crystal structure, the metal centre is surrounded by one carbonyl ligand, one triphenyl­phosphine ligand and the bidentate neocupferrate ligand, forming a distorted square-planar RhCO2P coordination set which is best illustrated by the small O—Rh—O bite angle of 77.74 (10)°. There are no classical hydrogen-bond inter­actions observed for this complex

Interpretable Machine Learning for Materials Design

Fueled by the widespread adoption of Machine Learning (ML) and the high-throughput screening of materials, the data-centric approach to materials design has asserted itself as a robust and powerful tool for the in-silico prediction of materials properties. When training models to predict material properties, researchers often face a difficult choice between a model's interpretability or its performance. We study this trade-off by leveraging four different state-of-the-art ML techniques: XGBoost, SISSO, Roost, and TPOT for the prediction of structural and electronic properties of perovskites and 2D materials. We then assess the future outlook of the continued integration of ML into materials discovery and identify key problems that will continue to challenge researchers as the size of the literature's datasets and complexity of models increases. Finally, we offer several possible solutions to these challenges with a focus on retaining interpretability and share our thoughts on magnifying the impact of ML on materials design

Spectral properties and magneto-optical excitations in semiconductor double-rings under Rashba spin-orbit interaction

We have numerically solved the Hamiltonian of an electron in a semiconductor double ring subjected to the magnetic flux and Rashba spin-orbit interaction. It is found that the Aharonov-Bohm energy spectrum reveals multi-zigzag periodic structures. The investigations of spin-dependent electron dynamics via Rabi oscillations in two-level and three-level systems demonstrate the possibility of manipulating quantum states. Our results show that the optimal control of photon-assisted inter-ring transitions can be achieved by employing cascade-type and $\Lambda$-type transition mechanisms. Under chirped pulse impulsions, a robust and complete transfer of an electron to the final state is shown to coincide with the estimation of the Landau-Zener formula.Comment: RevTex, 9 pages, 5 figure