Development and performance analysis of a saturated core high temperature superconducting fault current limiter

Recent international activity in the field of high voltage Fault Current Limiters (FCLs) has intensified since the North American blackout of 2003. A number of national and international peak body groups in the USA, Europe and Japan have been established to assess the need for FCLs and the issues associated with their design, specification, operation, protection and integration into the electricity grids. This paper details the development of a prototype 3-phase saturated core High Temperature Superconducting (HTS) FCL in Australia. Through experimental analysis, the performance of this device is characterised in terms of DC saturation, steady state performance, and fault current limiting ability

Fine and hyperfine resolved empirical energy levels of VO

A MARVEL (measured active rotational-vibrational energy levels) analysis of the spectra of vanadium oxide (VO) is performed, involving thirteen electronic states (6 quartets and 7 doublets). VO data from 14 sources are used to form three networks: hyperfine-resolved quartets, hyperfine-unresolved quartets and hyperfine-unresolved doublets. A single quartet network is formed by deperturbing the hyperfine lines and 191 lines are assigned to an intercombination 2 –X band system in the visible region previously recorded by Hopkins et al. (J. Chem. Phys. 130 (2009) 144308), allowing the doublet and quartet networks to be merged. As a result 6 603/4 402 validated transitions/final energies were obtained from analysis of the hyperfine-resolved network and 9 087/4 712 from the unresolved. energy values and other molecular constants are determined for all doublet states within the networks

Observational constraints on Cosmic Reionization

Recent observations have set the first constraints on the epoch of reionization (EoR), corresponding to the formation epoch of the first luminous objects. Studies of Gunn-Peterson (GP) absorption, and related phenomena, suggest a qualitative change in the state of the intergalactic medium (IGM) at $z \sim 6$, indicating a rapid increase in the neutral fraction of the IGM, from $x_{HI} 10^{-3}$, perhaps up to 0.1, at $z \ge 6$. Conversely, transmission spikes in the GP trough, and the evolution of the \lya galaxy luminosity function indicate $x_{HI} < 0.5$ at $z\sim 6.5$, while the large scale polarization of the cosmic microwave background (CMB) implies a significant ionization fraction extending to higher redshifts, $z \sim 11 \pm 3$. The results suggest that reionization is less an event than a process, with the process beginning as early as $z \sim 14$, and with the 'percolation', or 'overlap' phase ending at $z \sim 6$. The data are consistent with low luminosity star forming galaxies as being the dominant sources of reionizing photons. Low frequency radio telescopes currently under construction should be able to make the first direct measurements of HI 21cm emission from the neutral IGM during the EoR, and upcoming measurements of secondary CMB temperature anisotropy will provide fine details of the dynamics of the reionized IGM.Comment: to appear in ARAA 2006, vol 44, page 415-462; latex. 84 pages. 15 fi

The physical scale of the far-infrared emission in the most luminous submillimetre galaxies II: evidence for merger-driven star formation

We present high-resolution 345 GHz interferometric observations of two extreme luminous (L_{IR}>10^{13} L_sun), submillimetre-selected galaxies (SMGs) in the COSMOS field with the Submillimeter Array (SMA). Both targets were previously detected as unresolved point-sources by the SMA in its compact configuration, also at 345 GHz. These new data, which provide a factor of ~3 improvement in resolution, allow us to measure the physical scale of the far-infrared in the submillimetre directly. The visibility functions of both targets show significant evidence for structure on 0.5-1 arcsec scales, which at z=1.5 translates into a physical scale of 5-8 kpc. Our results are consistent with the angular and physical scales of two comparably luminous objects with high-resolution SMA followup, as well as radio continuum and CO sizes. These relatively compact sizes (<5-10 kpc) argue strongly for merger-driven starbursts, rather than extended gas-rich disks, as the preferred channel for forming SMGs. For the most luminous objects, the derived sizes may also have important physical consequences; under a series of simplifying assumptions, we find that these two objects in particular are forming stars close to or at the Eddington limit for a starburst.Comment: 9 pages, 3 Figures, submitted to MNRA

A parallelized molecular collision cross section package with optimized accuracy and efficiency

Ion mobility-based separation prior to mass spectrometry has become an invaluable tool in the structural elucidation of gas-phase ions and in the characterization of complex mixtures. Application of ion mobility to structural studies requires an accurate methodology to bridge theoretical modelling of chemical structure with experimental determination of an ion's collision cross section (CCS). Herein, we present a refined methodology for calculating ion CCS using parallel computing architectures that makes use of atom specific parameters, which we have called MobCal-MPI. Tuning of ion-nitrogen van der Waals potentials on a diverse calibration set of 162 molecules returned a RMSE of 2.60% in CCS calculations of molecules containing the elements C, H, O, N, F, P, S, Cl, Br, and I. External validation of the ion-nitrogen potential was performed on an additional 50 compounds not present in the validation set, returning a RMSE of 2.31% for the CCSs of these compounds. Owing to the use of parameters from the MMFF94 forcefield, the calibration of the van der Waals potential can be extended to additional atoms defined in the MMFF94 forcefield (i.e., Li, Na, K, Si, Mg, Ca, Fe, Cu, Zn). We expect that the work presented here will serve as a foundation for facile determination of molecular CCSs, as MobCal-MPI boasts up to 64-fold speedups over traditional calculation packages.The authors would like to acknowledge the financial support provided by the Natural Sciences and Engineering Research Council (NSERC) of Canada

Janus face aspect of all-cis 1,2,3,4,5,6-hexafluorocyclohexane dictates remarkable anion and cation interactions in the gas phase

The authors acknowledge support in the form of NSERC (Canada) Discovery Grants to EF, WSH, and TBM and an EPSRC (UK) responsive mode grant to DO’H and NSK is gratefully acknowledged.Experiments have been carried out in which electrospray ionization has been used to generate ionic complexes of all-cis 1,2,3,4,5,6 hexafluorocyclohexane. These complexes were subsequently mass isolated in a quadrupole ion trap mass spectrometer and then irradiated by the tunable infrared output of a free electron laser in the 800-1600 cm−1 range. From the frequency dependence of the fragmentation of the complexes, vibrational signatures of the complexes were obtained. Computational work carried out in parallel reveals that the complexes formed are very strongly bound and are among the most strongly bound complexes of Na+ and Cl− ever observed with molecular species. The dipole moment calculated for the heaxafluorocyclohexane is very large (~7 D) and it appears that the bonding in each of the complexes has a significant electrostatic contribution.PostprintPeer reviewe

Resolving the Radio Source Background: Deeper Understanding Through Confusion

We used the Karl G. Jansky Very Large Array (VLA) to image one primary beam area at 3 GHz with 8 arcsec FWHM resolution and 1.0 microJy/beam rms noise near the pointing center. The P(D) distribution from the central 10 arcmin of this confusion-limited image constrains the count of discrete sources in the 1 < S(microJy/beam) < 10 range. At this level the brightness-weighted differential count S^2 n(S) is converging rapidly, as predicted by evolutionary models in which the faintest radio sources are star-forming galaxies; and ~96$% of the background originating in galaxies has been resolved into discrete sources. About 63% of the radio background is produced by AGNs, and the remaining 37% comes from star-forming galaxies that obey the far-infrared (FIR) / radio correlation and account for most of the FIR background at lambda = 160 microns. Our new data confirm that radio sources powered by AGNs and star formation evolve at about the same rate, a result consistent with AGN feedback and the rough correlation of black hole and bulge stellar masses. The confusion at centimeter wavelengths is low enough that neither the planned SKA nor its pathfinder ASKAP EMU survey should be confusion limited, and the ultimate source detection limit imposed by "natural" confusion is < 0.01 microJy at 1.4 GHz. If discrete sources dominate the bright extragalactic background reported by ARCADE2 at 3.3 GHz, they cannot be located in or near galaxies and most are < 0.03 microJy at 1.4 GHz.Comment: 28 pages including 16 figures. ApJ accepted for publicatio

Ligand Specificity and Affinity in the Sulforhodamine B Binding RNA Aptamer

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.bbrc.2020.06.056. © 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Binding affinity and selectivity are critical properties of aptamers that must be optimized for any application. The sulforhodamine B binding RNA aptamer (SRB‐2) is a somewhat promiscuous aptamer that can bind ligands that vary markedly in shape, size and charge. Here we categorize potential ligands based on their binding mode and structural characteristics required for high affinity and selectivity. Several known and potential ligands of SRB‐2 were screened for binding affinity using LSPR, ITC and NMR spectroscopy. The study shows that rhodamine B has the ideal structural and electrostatic properties for selective and high‐affinity binding of the SRB‐2 aptamer.NSERC Discovery Grant 30345