Adaptive AoA estimation and beamforming with hybrid antenna arrays

A new type of hybrid antenna array consisting of analogue subarrays followed by a digital beamformer is proposed for practical implementation of long range high data rate millimetre wave communications systems. An adaptive algorithm, referred to as the differential beam search (DBS), is proposed for the angle of arrival (AoA) estimation to control the phase shifters in the analogue subarrays and to perform digital beamforming. This algorithm does not need the knowledge of a reference signal and effectively solves the phase ambiguity problem in AoA estimation inherent to the practical subarray configuration. The performance of the proposed DBS algorithms is demonstrated by simulations. © 2009 IEEE

Extrapolations of Lattice Meson Form Factors

We use chiral perturbation theory to study the extrapolations necessary to make physical predictions from lattice QCD data for the electromagnetic form factors of pseudoscalar mesons. We focus on the quark mass, momentum, lattice spacing, and volume dependence and apply our results to simulations employing mixed actions of Ginsparg-Wilson valence quarks and staggered sea quarks. To determine charge radii at quark masses on the lattices currently used, we find that all extrapolations except the one to infinite volume make significant contributions to the systematic error.Comment: 14pp, discussion and Ref. added for disconnected diagram

PKSB1740-517: An ALMA view of the cold gas feeding a distant interacting young radio galaxy

Cold neutral gas is a key ingredient for growing the stellar and central black hole mass in galaxies throughout cosmic history. We have used the Atacama Large Millimetre Array (ALMA) to detect a rare example of redshifted $^{12}$CO(2-1) absorption in PKS B1740-517, a young ($t \sim 1.6 \times 10^{3}$ yr) and luminous ($L_{\rm 5 GHz} \sim 6.6 \times 10^{43}$ erg s$^{-1}$ ) radio galaxy at $z = 0.44$ that is undergoing a tidal interaction with at least one lower-mass companion. The coincident HI 21-cm and molecular absorption have very similar line profiles and reveal a reservoir of cold gas ($M_{\rm gas} \sim 10^{7} - 10^{8}$ M$_{\odot}$), likely distributed in a disc or ring within a few kiloparsecs of the nucleus. A separate HI component is kinematically distinct and has a very narrow line width ($\Delta{v}_{\rm FWHM} \lesssim 5$ km s$^{-1}$), consistent with a single diffuse cloud of cold ($T_{\rm k} \sim 100$ K) atomic gas. The $^{12}$CO(2-1) absorption is not associated with this component, which suggests that the cloud is either much smaller than 100 pc along our sight-line and/or located in low-metallicity gas that was possibly tidally stripped from the companion. We argue that the gas reservoir in PKS B1740-517 may have accreted onto the host galaxy $\sim$50 Myr before the young radio AGN was triggered, but has only recently reached the nucleus. This is consistent with the paradigm that powerful luminous radio galaxies are triggered by minor mergers and interactions with low-mass satellites and represent a brief, possibly recurrent, active phase in the life cycle of massive early type galaxies.Comment: 15 pages, 7 figures, accepted for publication in MNRA

Multi-Gigabit Wireless Link Development

CSIRO ICT Centre is developing millimetre wave point-to-point links suitable for multi-gigabit wireless connectivity. Suitable spectrum for this purpose is allocated at the 60 GHz band and above. This paper reports a new point-to-point link that will be installed at Marsfield site to demonstrate multi-gigabit operation and performance of its key components. The link will operate at the 81-86 GHz band incorporating CSIRO designed millimetre wave MMICs and multi-gigabit modems

Pion mass dependence of the Kl3K_{l3} semileptonic scalar form factor within finite volume

We calculate the scalar semileptonic kaon decay in finite volume at the momentum transfer $t_{m} = (m_{K} - m_{\pi})^2$, using chiral perturbation theory. At first we obtain the hadronic matrix element to be calculated in finite volume. We then evaluate the finite size effects for two volumes with $L = 1.83 fm$ and $L= 2.73 fm$ and find that the difference between the finite volume corrections of the two volumes are larger than the difference as quoted in \cite{Boyle2007a}. It appears then that the pion masses used for the scalar form factor in ChPT are large which result in large finite volume corrections. If appropriate values for pion mass are used, we believe that the finite size effects estimated in this paper can be useful for Lattice data to extrapolate at large lattice size.Comment: 19 pages, 5 figures, accepted for publication in EPJ

Molecular profiling of multiplexed gene markers to assess viability of ex vivo human colon explant cultures

© Janice E. Drew et al. 2015; Published by Mary Ann Liebert, Inc. This Open Access article is distributed under the terms of the Creative Commons License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. Acknowledgments The authors would like to thank the patients who kindly donated tissue samples, Sally Chalmers of the Tayside Tissue Bank for her help with collecting of the tissue donor samples, Emma Moss for advice on human colon dissection and explant culture, and Claus Dieter Mayer, Biomathematics and Statistics Scotland, for advice on statistical analysis. This work was supported by the Scottish Government (GT403), Scottish Universities Life Science Alliance, and TENOVUS Scotland.Peer reviewedPublisher PD

A Giant Outburst at Millimeter Wavelengths in the Orion Nebula

BIMA observations of the Orion nebula discovered a giant flare from a young star previously undetected at millimeter wavelengths. The star briefly became the brightest compact object in the nebula at 86 GHz. Its flux density increased by more than a factor of 5 on a timescale of hours, to a peak of 160 mJy. This is one of the most luminous stellar radio flares ever observed. Remarkably, the Chandra X-ray observatory was in the midst of a deep integration of the Orion nebula at the time of the BIMA discovery; the source's X-ray flux increased by a factor of 10 approximately 2 days before the radio detection. Follow-up radio observations with the VLA and BIMA showed that the source decayed on a timescale of days, then flared again several times over the next 70 days, although never as brightly as during the discovery. Circular polarization was detected at 15, 22, and 43 GHz, indicating that the emission mechanism was cyclotron. VLBA observations 9 days after the initial flare yield a brightness temperature Tb > 5 x 10^7 K at 15 GHz. Infrared spectroscopy indicates the source is a K5V star with faint Br gamma emission, suggesting that it is a weak-line T Tauri object. Zeeman splitting measurements in the infrared spectrum find B ~ 2.6 +/- 1.0 kG. The flare is an extreme example of magnetic activity associated with a young stellar object. These data suggest that short observations obtained with ALMA will uncover hundreds of flaring young stellar objects in the Orion region.Comment: 29 pages, 7 figures, accepted for publication in Ap