Radio Cores in Low-Luminosity AGN: ADAFs or Jets?

We have surveyed two large samples of nearby low-luminosity AGN with the VLA to search for flat-spectrum radio cores, similar to Sgr A* in the Galactic Center. Roughly one third of all galaxies are detected (roughly one half if HII transition objects are excluded from the sample), many of which have compact radio cores. Follow-up observations with the VLBA have confirmed that these cores are non-thermal in origin, with lower limits for the brightness temperatures around ~10^8 K. The brightest of these are resolved into linear structures. The radio spectral indices of the cores are quite flat (alpha~0), with no evidence for the highly inverted radio cores predicted in the ADAF model. Spectrum and morphology of the compact radio emission is typical for radio jets seen also in more luminous AGN. The emission-line luminosity seems to be correlated with the radio core flux. Together with the VLBI observations this suggests that optical and radio emission in at least half the low-luminosity Seyferts and LINERs are black hole powered. We find only a weak correlation between bulge luminosity and radio flux and an apparently different efficiency between elliptical and spiral galaxies for producing radio emission at a given optical luminosity.Comment: 5 pages, 2 figures, (ESO) LaTex, to appear in ``Black Holes in Binaries and Galactic Nuclei'', ESO workshop, eds. L. Kaper, E.P.J. van den Heuvel, P.A. Woudt, Springer Verlag; also available at http://www.mpifr-bonn.mpg.de/staff/hfalcke/publications.html#eso9

Cognitive Mechanisms in Chronic Tinnitus: Psychological Markers of a Failure to Switch Attention

The cognitive mechanisms underpinning chronic tinnitus (CT; phantom auditory perceptions) are underexplored but may reflect a failure to switch attention away from a tinnitus sound. Here, we investigated a range of components that influence the ability to switch attention, including cognitive control, inhibition, working memory and mood, on the presence and severity of CT. Our participants with tinnitus showed significant impairments in cognitive control and inhibition as well as lower levels of emotional well-being, compared to healthy-hearing participants. Moreover, the subjective cognitive complaints of tinnitus participants correlated with their emotional well-being whereas complaints in healthy participants correlated with objective cognitive functioning. Combined, cognitive control and depressive symptoms correctly classified 67% of participants. These results demonstrate the core role of cognition in CT. They also provide the foundations for a neurocognitive account of the maintenance of tinnitus, involving impaired interactions between the neurocognitive networks underpinning attention-switching and mood

The Murmur of the Sleeping Black Hole: Detection of Nuclear Ultraviolet Variability in LINER Galaxies

LINER nuclei, which are present in many nearby galactic bulges, may be the manifestation of low-rate or low-radiative-efficiency accretion onto supermassive central black holes. However, it has been unclear whether the compact UV nuclear sources present in many LINERs are clusters of massive stars, rather than being directly related to the accretion process. We have used HST to monitor the UV variability of a sample of 17 galaxies with LINER nuclei and compact nuclear UV sources. Fifteen of the 17 galaxies were observed more than once, with two to five epochs per galaxy, spanning up to a year. We detect significant variability in most of the sample, with peak-to-peak amplitudes from a few percent to 50%. In most cases, correlated variations are seen in two independent bands (F250W and F330W). Comparison to previous UV measurements indicates, for many objects, long-term variations by factors of a few over decade timescales. Variability is detected in LINERs with and without detected compact radio cores, in LINERs that have broad H-alpha wings detected in their optical spectra (``LINER 1's''), and in those that do not (``LINER 2s''). This variability demonstrates the existence of a non-stellar component in the UV continuum of all types, and sets a lower limit to the luminosity of this component. We note a trend in the UV color (F250W/F330W) with spectral type - LINER 1s tend to be bluer than LINER 2s. This trend may indicate a link between the shape of the nonstellar continuum and the presence or the visibility of a broad-line region. In one target, the post-starburst galaxy NGC 4736, we detect variability in a previously noted UV source that is offset by 2.5" (60 pc in projection) from the nucleus. This may be the nearest example of a binary active nucleus, and of the process leading to black hole merging.Comment: accepted to Ap

Reducing long distance truck driver’s intention to leave: An analysis of professional drivers and owner operators using importance/performance methods

Since it is widely known that turnover is highest among unsatisfied employees, the authors argue that long haul professional drivers (PDs) and owner operators (OOs) can be retained by using a yearly importance/performance analysis of company drivers. Because qualified drivers are becoming more scarce and difficult to recruit/retain, carriers need to focus on increasing driver retention. In this article, we suggest an Importance/Performance (IP) model which uses an “if then” perspective, relating intention to leave as a function of the PD/OO: IP structure. This model is used to explain the managerial changes that could be made to retain professional drivers and owner operators

Using Spatial Manipulation to Examine Interactions between Visual and Auditory Encoding of Pitch and Time

Music notations use both symbolic and spatial representation systems. Novice musicians do not have the training to associate symbolic information with musical identities, such as chords or rhythmic and melodic patterns. They provide an opportunity to explore the mechanisms underpinning multimodal learning when spatial encoding strategies of feature dimensions might be expected to dominate. In this study, we applied a range of transformations (such as time reversal) to short melodies and rhythms and asked novice musicians to identify them with or without the aid of notation. Performance using a purely spatial (graphic) notation was contrasted with the more symbolic, traditional western notation over a series of weekly sessions. The results showed learning effects for both notation types, but performance improved more for graphic notation. This points to greater compatibility of auditory and visual neural codes for novice musicians when using spatial notation, suggesting that pitch and time may be spatially encoded in multimodal associative memory. The findings also point to new strategies for training novice musicians