Interstellar Mg II and C IV absorption by 1 1/2 galaxies along the sightline to MrK 205

The first results of our HST survey designed to search for Mg 2 and C 4 absorption lines from the disks and halos of low-redshift galaxies using background QSO's and supernovae as probes are presented. Our survey utilizes the high resolution of the Goddard High Resolution Spectrograph enabling us to calculate the column densities and doppler parameters of individual components within an absorption complex, and hence determine the physical conditions of the absorbing gas. Observing the complexity of the absorption line profiles i.e., the velocity distribution and total velocity extent of the constituent components, offers an important description of the kinematics of the absorbing gas, and hence an understanding of its origin. Focus is on one sight line in particular, that towards Mrk 205, which passes 3-5 kpc from the intervening galaxy NGC 4319. Mg 2 and C 4 absorption from both local Milky Way halo gas and from NGC 4319 is detected

The Detection of Lyman-alpha Absorption from Nine Nearby Galaxies

We have used STIS aboard HST to search for Lyman-alpha (Lya) absorption in the outer regions of nine nearby (cz<6000 km/s) galaxies using background QSOs and AGN as probes. The foreground galaxies are intercepted between 26 and 199 h-1 kpc from their centers, and in all cases we detect Lya within +/-500 km/s of the galaxies' systemic velocities. The intervening galaxies have a wide range of luminosities, from M_B = -17.1 to -20.0, and reside in various environments: half the galaxies are relatively isolated, the remainder form parts of groups or clusters of varying richness. The equivalent widths of the Lya lines range from 0.08 - 0.68 A and, with the notable exception of absorption from one pair, crudely correlate with sightline separation in a way consistent with previously published data, though the column densities derived from the lines do not. The lack of correlation between line strength and galaxy luminosity or, in particular, the environment of the galaxy, suggests that the absorption is not related to any individual galaxy, but arises in gas which follows the same dark-matter structures that the galaxies inhabit.Comment: 8 pages, invited review to appear in the proceedings of the Yale Cosmology Workshop on `The Shapes of Galaxies & their Halos", P. Natarajan, ed. Best figures found in (17Mb) PS file at http://astro.princeton.edu/~dvb/yale.p

Physical insight into reduced surface roughness scattering in strained silicon inversion layers

A seemingly anomalous enhancement of electron mobility in strained silicon inversion layers at high sheet densities has exposed a conspicuous gap between device physics theory and experiment in recent years. We show that the root of this discrepancy is due to a bulging effect in the electron \Delta 4 wavefunction at the silicon surface. This renders \Delta 4 electrons more susceptible to perturbations in surface structure thereby increasing surface roughness scattering for these states. Strain engineering utilized by the CMOS industry reduces the relative occupancy of the \Delta 4 states resulting in less overall surface roughness scattering in the channel. We show that the origin of this effect can be explained by moving beyond the effective mass approximation and contrasting the properties of the \Delta 2 and \Delta 4 wavefunctions in a representation that comprehends full crystal and Bloch state symmetry.Comment: 5 pages, 6 figures. Submitted to Applied Physics Letters on 4 April 2012. Update

Acquisition, representation and rule generation for procedural knowledge

Current research into the design and continuing development of a system for the acquisition of procedural knowledge, its representation in useful forms, and proposed methods for automated C Language Integrated Production System (CLIPS) rule generation is discussed. The Task Analysis and Rule Generation Tool (TARGET) is intended to permit experts, individually or collectively, to visually describe and refine procedural tasks. The system is designed to represent the acquired knowledge in the form of graphical objects with the capacity for generating production rules in CLIPS. The generated rules can then be integrated into applications such as NASA's Intelligent Computer Aided Training (ICAT) architecture. Also described are proposed methods for use in translating the graphical and intermediate knowledge representations into CLIPS rules

Redshifts of galaxies close to bright QSO lines of sight

To expand the known number of low-redshift galaxies which lie close to bright ($V < 17.2$) QSO lines of sight, we have identified 24 galaxies within 11 arcmins of nine QSOs which have been observed with the Hubble Space Telescope (HST). Galaxies are found between redshifts of $0.0114-0.145$ and lie between $39-749$ $h^{-1}$ kpc from QSO sightlines. Knowing the redshifts of these galaxies has already proved important in understanding results from HST programmes designed to search for UV absorption lines from low-redshift galaxies, and will enable future observations to probe the halos of these galaxies in detail.Comment: MNRAS in press. 9 pages LaTeX using MNRAS sty. Postscript figures are excluded due to large size. Paper with figures can be obtained from http://www.roe.ac.uk/research/bowen1.ps.