2,247 research outputs found

    Internal Kinematics of Distant Field Galaxies: I. Emission Line Widths for a Complete Sample of Faint Blue Galaxies at <z>=0.25

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    We present measurements of the OII(3727) emission line width for a complete sample of 24 blue field galaxies (21.25=0.25, obtained with the AUTOFIB fibre spectrograph on the Anglo-Australian Telescope. Most emission lines are spectrally resolved, yet all have dispersions sigma<100km/s. Five of the 24 sample members have OII doublet line flux ratios which imply gas densities in excess of 100 cm^-3. The line emission in these galaxies may be dominated by an active nucleus and the galaxies have been eliminated from the subsequent analysis. The remaining 19 linewidths are too large by a factor of two (7sigma significance) to be attributed to turbulent motions within an individual star forming region, and therefore most likely reflect the orbital motion of ionized gas in the galaxy. We use Fabry--Perot observations of nearby galaxies to construct simulated datasets that mimic our observational setup at z=0.25; these allow us to compute the expected distribution of (observable) linewidths sigma_v for a galaxy of a given ``true'' (optical) rotation speed v_c. These simulations include the effects of random viewing angles, clumpy line emission, finite fibre aperture, and internal dust extinction on the emission line profile. We assume a linewidth--luminosity--colour relation: ln[ v_c(M_B,B-R) ] = ln[v_c(-19,1)] - eta*(M_B+10) + zeta*[(B-R)-1] and determine the range of parameters consistent with our data. We find a mean rotation speed of v_c(-19,1)=66+-8km/s (68% confidence limits) for the distant galaxies with M_B=-19 and B-R=1, with a magnitude dependence for v_c of eta=0.07+-0.08, and a colour dependence of zeta =0.28+-0.25. Through comparison with several local samples we show that this value of v_c(-19,1) is significantly lower than the optical rotation speed of present-day galaxies with the same absolute magnitudeComment: TeX Text and Tables, no Figures. Compressed and uuencoded PS file of the complete paper (43 pages including 9 figures) available at http://zwicky.as.arizona.edu/~rix/; submitted to MNRA

    Cultivation and analysis of anthocyanins containing-, blue potatoes

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    Anthocyanins, as secondary plant substance in different agricultural crops such as potatoes and cereals have positive effects on health due to their antioxidant capacity. Therefore food industry, nutritional medicine and consumers have an increasing interest in these crops. The objectives of the interdisciplinary research project (AGIP) starting in march 2006 are ascertainment and assessment of the impact of different agricultural production processes and production intensities. Furthermore, the impact of different ways of food preparation concerning anthocyanin content and antioxidative capacity in selected cultivated plants will be tested. Main focus will be on potatoes due to the fact that potatoes as a staple food are consumed in large quantities. Therefore potatoes can be an important quantitative source for anthocyanins

    Investigation of a Second Exhaust Valve Lift to Improve Combustion in a Methane - Diesel Dual-Fuel Engine

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    In recent years, the utilization of dual-fuel combustion has gained popularity in order to improve engine efficiency and emissions. With its high knock resistance, methane allows operation in high compression diesel engines with lower risk of knocking. With the use of diesel fuel as an ignition source, it is possible to exploit the advantages of lean combustion without facing problems to provide the high amount of ignition energy necessary to burn methane under such operating conditions. Another advantage is the variety of sources from which the primary fuel can be obtained. In addition to fossil sources, methane can also be produced from biomass or electrical energy. As the rate of substitution of diesel by methane increases, the trade- off between nitrogen oxide and soot is mitigated. However, emissions of carbon monoxide and unburned methane increase. Since carbon monoxide is toxic and methane has 25 times the global warming potential of carbon dioxide, these emission components pose a problem. Because of the stability of the molecule, methane catalysts require an exhaust gas temperature of over 500 °C in order to work effectively. In this work, the effect of conventional cooled external exhaust gas recirculation (EGR) and additional hot internal EGR are investigated for different substitution rates in a nonroad tractor engine converted to dual-fuel operation. The internal EGR rate is controlled by a variable second exhaust valve lift during the intake stroke – an approach which promises to benefit dual-fuel engines by increasing the in-cylinder gas temperature, thus favoring more complete combustion. A simulation model of the engine is used to determine the internal EGR rates and in-cylinder temperatures based on the experimental data. When internal EGR is used in combination with external EGR, the resulting emissions show additional reductions in nitrogen oxide (up to -51 %), carbon monoxide (up to -18 %) and methane (up to -28 %) with increasing internal EGR, while still maintaining low soot levels due to the substitution of diesel fuel for methane

    Consolidation of complex events via reinstatement in posterior cingulate cortex

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    It is well-established that active rehearsal increases the efficacy of memory consolidation. It is also known that complex events are interpreted with reference to prior knowledge. However, comparatively little attention has been given to the neural underpinnings of these effects. In healthy adult humans, we investigated the impact of effortful, active rehearsal on memory for events by showing people several short video clips and then asking them to recall these clips, either aloud (Experiment 1) or silently while in an MRI scanner (Experiment 2). In both experiments, actively rehearsed clips were remembered in far greater detail than unrehearsed clips when tested a week later. In Experiment 1, highly similar descriptions of events were produced across retrieval trials, suggesting a degree of semanticization of the memories had taken place. In Experiment 2, spatial patterns of BOLD signal in medial temporal and posterior midline regions were correlated when encoding and rehearsing the same video. Moreover, the strength of this correlation in the posterior cingulate predicted the amount of information subsequently recalled. This is likely to reflect a strengthening of the representation of the video's content. We argue that these representations combine both new episodic information and stored semantic knowledge (or "schemas"). We therefore suggest that posterior midline structures aid consolidation by reinstating and strengthening the associations between episodic details and more generic schematic information. This leads to the creation of coherent memory representations of lifelike, complex events that are resistant to forgetting, but somewhat inflexible and semantic-like in nature

    KREMLAS: Entwicklung einer kreativen evolutionĂ€ren Entwurfsmethode fĂŒr Layoutprobleme in Architektur und StĂ€dtebau

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    Die im vorliegenden Buch dokumentierten Untersuchungen befassen sich mit der Entwicklung von Methoden zur algorithmischen Lösung von Layoutaufgaben im architektonischen Kontext. Layout bezeichnet hier die gestalterisch und funktional sinnvolle Anordnung rĂ€umlicher Elemente, z.B. von Parzellen, GebĂ€uden, RĂ€umen auf bestimmten Maßstabsebenen. Die vorliegenden Untersuchungen sind im Rahmen eines von der Deutschen Forschungsgemeinschaft geförderten Forschungsprojekts entstanden
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