Asteroseismic Signatures of Stellar Magnetic Activity Cycles

Observations of stellar activity cycles provide an opportunity to study magnetic dynamos under many different physical conditions. Space-based asteroseismology missions will soon yield useful constraints on the interior conditions that nurture such magnetic cycles, and will be sensitive enough to detect shifts in the oscillation frequencies due to the magnetic variations. We derive a method for predicting these shifts from changes in the Mg II activity index by scaling from solar data. We demonstrate this technique on the solar-type subgiant beta Hyi, using archival International Ultraviolet Explorer spectra and two epochs of ground-based asteroseismic observations. We find qualitative evidence of the expected frequency shifts and predict the optimal timing for future asteroseismic observations of this star.Comment: 5 pages including 3 figures and 1 table, MNRAS Letters accepte

Times, life and thought of Patrick Forbes, Bishop of Aberdeen 1618 - 1635

There has only been one attempt to construct anything like a full account of the life of Patrick Forbes. This was by G.P.Shand in his introduction to the funeral orations and pieces offered in honour of the Bishop and published by the Spottiswoode Society in 1845. Shand's Memoir is valuable but enters into no detailed analysis of Forbes's thought, nor of the movements of the time which formed the background of his life and in which he played a notable part. The author is content to follow the brief references of Garden to the Bishops work as Chancellor of Aberdeen University and does not attempt to assess the extent of his influence upon seventeenth century religious life and thought. Besides Shand did not have before him the printed editions of the Register of the Privy Council of Scotland which throw additional and interesting light upon Forbes as a statesman and a diocesan.A recent valuable addition to a fuller understanding of the life and influence of Patrick Forbes is contained in Professor G. D. Henderson's Religious Life in Seventeenth Century Scotland. The most useful parts of Henderson's essay on Forbes are those which deal with his work in connection with King's College, Aberdeen and his influence throughout the remainder of the seventeenth century. Henderson helps us to fill in the gaps left by Shand and I gladly acknowledge my indebtedness to these two scholars.A recent valuable addition to a fuller understanding of the life and influence of Patrick Forbes is contained in Professor G. D. Henderson's Religious Life in Seventeenth Century Scotland. The most useful parts of Henderson's essay on Forbes are those which deal with his work in connection with King's College, Aberdeen and his influence throughout the remainder of the seventeenth century. Henderson helps us to fill in the gaps left by Shand and I gladly acknowledge my indebtedness to these two scholars.It has been said that when God appoints a man to some special work or witness His preparatory action is to be seen in the circumstances of hereditary descent. Forbes's ancestry has been fully explored in Chapter 1 with such comment as appeared necessary and his degree of kinship with Andrew Melville, usually left vague, indicated. From time to time suggestions which seemed historically reasonable have been offered and erroneous or misleading statements challenged. Material not previously used by those who have written of Patrick Forbes, from Registers of the Privy Council of Scotland and from the Ecclesiastical Records of Aberdeen, has been used, while the closest attention has been given to Forbes's own writings.It has not been easy to keep Forbes continually in the picture, but I have tried, chiefly by use of Appendices, to avoid Russell Lowell's criticism of Masson's Life of Milton - that Milton was sometimes only an incident in his own biography. Opportunity has been taken to explain the principles governing Episcopal Elections during the First Scottish Episcopate and to elucidate other points frequently omitted or glossed over in text books. Particularly have I tried to stress the decisive nature of the economic and political motives which underlay the national Covenant of 1638, for these nave not been correctly guaged by Episcopalian historians who have too frequently tended to represent the issue as a clear-cut one between Episcopacy and Presbyterianism

The rate of mass loss and variations in the wind from the Be star delta Centauri

Copernicus ultraviolet scans of the Be star delta Centauri obtained in 1976 and 1979, show a significant variation in the Si III lambda 1206 profile, The strong asymmetry that was present in 1976 had disappeared by 1979. The Si IV lambda 1400 doublet was also asymmetric in 1976, but was not observed in 1979. A quantitative fit of the line shapes to theoretical wind profiles shows that the mass-loss rate in 1976 was 2 x 10 to the minus 8th power/yr, and that the rate of mass loss in Si III was at least one order of magnitude less in 1979. It is not possible to determine whether the variation represented an overall change in the lass-loss rate, or whether it was due to a change in the ionization balance. The profile fitting procedure resulted in the adoption of assumed underlying photospheric Si III and Si IV profiles, and the equivalent widths measured from these profiles are most consistent with T sub eff between 30,000 and 35,000 K, somewhat hotter than implied by the spectral classification normally assigned to this star. The ultraviolet photospheric line widths, coupled wit published theoretical analyses of rotational gravitational darkening, imply an intrinsic equatorial velocity of about 310 km/sec and an angle of inclination of the rotational axis to the line of sight of i is less than or equal to 44 deg

Si nanostructures fabricated by anodic oxidation with an atomic force microscope and etching with an electron cyclotron resonance source

Nanometer‐scale Si structures have been fabricated by anodic oxidation with an atomic force microscope (AFM) and dry etching using an electron cyclotron resonance (ECR) source. The AFM is used to anodically oxidize a thin surface layer on a H‐passivated (100) Si surface. This oxide is used as a mask for etching in a Cl2 plasma generated by the ECR source. An etch selectivity ≳20 was obtained by adding 20% O2 to the Cl2 plasma. The AFM‐defined mask withstands a 70 nm deep etch, and linewidths∼10 nm have been obtained with a 30 nm etch depth. © 1995 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70639/2/APPLAB-66-14-1729-1.pd

Precision determination of absolute neutron flux

A technique for establishing the total neutron rate of a highly-collimated monochromatic cold neutron beam was demonstrated using a method of an alpha-gamma counter. The method involves only the counting of measured rates and is independent of neutron cross sections, decay chain branching ratios, and neutron beam energy. For the measurement, a target of 10B-enriched boron carbide totally absorbed the neutrons in a monochromatic beam, and the rate of absorbed neutrons was determined by counting 478keV gamma rays from neutron capture on 10B with calibrated high-purity germanium detectors. A second measurement based on Bragg diffraction from a perfect silicon crystal was performed to determine the mean de Broglie wavelength of the beam to a precision of 0.024 %. With these measurements, the detection efficiency of a neutron monitor based on neutron absorption on 6Li was determined to an overall uncertainty of 0.058 %. We discuss the principle of the alpha-gamma method and present details of how the measurement was performed including the systematic effects. We also describe how this method may be used for applications in neutron dosimetry and metrology, fundamental neutron physics, and neutron cross section measurements.Comment: 44 page

ICONA: Inter Cluster ONOS Network Application

Several Network Operating Systems (NOS) have been proposed in the last few years for Software Defined Networks; however, a few of them are currently offering the resiliency, scalability and high availability required for production environments. Open Networking Operating System (ONOS) is an open source NOS, designed to be reliable and to scale up to thousands of managed devices. It supports multiple concurrent instances (a cluster of controllers) with distributed data stores. A tight requirement of ONOS is that all instances must be close enough to have negligible communication delays, which means they are typically installed within a single datacenter or a LAN network. However in certain wide area network scenarios, this constraint may limit the speed of responsiveness of the controller toward network events like failures or congested links, an important requirement from the point of view of a Service Provider. This paper presents ICONA, a tool developed on top of ONOS and designed in order to extend ONOS capability in network scenarios where there are stringent requirements in term of control plane responsiveness. In particular the paper describes the architecture behind ICONA and provides some initial evaluation obtained on a preliminary version of the tool.Comment: Paper submitted to a conferenc