1,182 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
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
Consolidation of complex events via reinstatement in posterior cingulate cortex
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
Bloch-Redfield equations for modeling light-harvesting complexes
We challenge the misconception that Bloch-Redfield equations are a less
powerful tool than phenomenological Lindblad equations for modeling exciton
transport in photosynthetic complexes. This view predominantly originates from
an indiscriminate use of the secular approximation. We provide a detailed
description of how to model both coherent oscillations and several types of
noise, giving explicit examples. All issues with non-positivity are overcome by
a consistent straightforward physical noise model. Herein also lies the
strength of the Bloch-Redfield approach because it facilitates the analysis of
noise-effects by linking them back to physical parameters of the noise
environment. This includes temporal and spatial correlations and the strength
and type of interaction between the noise and the system of interest. Finally
we analyze a prototypical dimer system as well as a 7-site Fenna-Matthews-Olson
(FMO) complex in regards to spatial correlation length of the noise, noise
strength, temperature and their connection to the transfer time and transfer
Use of Gas Emulsion in Blasting Project for Clearing in a Copper Mine in Southern Peru
The gasifiable emulsion is a technological and productive response to the need to reduce operating costs in the mining project, among the improvements with respect to ANFO are a higher detonation velocity (VOD), better fragmentation and reduction of nitrous fumes. In the test mining operation, a commercial explosive mixture called "Q "73 (70% emulsion and 30% ANFO) is used, where the ANFO is composed of 97% ammonium nitrate and 3% diesel, and the explosive mixture "Q "82 (80% emulsion and 20% ANFO) is also used, 7 blasting processes were carried out with a diameter of 12.25 in. in a waste area, the most characteristic rocks found in the blasting project in the copper mine in southern Peru are Toba Cristal (TC), Andesite Basaltic Propylitic (BA-PRO), Andesite Basaltic Argillic (BA-ARG). The results obtained show a reduction of the Power Factor by 1.32%, with respect to the commercial mixtures "Q "73 and "Q "82 an optimum increase in the detonation velocity of 9.92% and 0.59% was obtained, also the high-resolution images of the fumes after blasting indicate a low presence of orange fumes taking a great relevance in the mining sector on a large scale, achieving better results in the blasting phase
Pengaruh Pengunaan Katalis Terhadap Laju Dan Efisiensi Pembentukan Hidrogen
Hydrogen was produced by steam reforming of kapok seed oil. CuZn as catalyst helps accelerate separation and increase production of hydrogen gas. This catalyst is viable and has high stability. Hydrogen gas was produced through 3 steps of catalyzing by mixed kapok seed oil and water with ratio of 1:1, 1:3 and 3:1. Heating temperature of catalyst at 250 C was selected. The rate and efficiency in forming of hydrogen gas were evaluated. From present investigation show that the more steps of catalyzing resulted in higher products, production rate, and efficiency in forming of hydrogen gas. Using 3 steps of catalyzing has promoted higher products, production rate, and efficiency in forming of hydrogen gas compared to 1 step and 2 step of catalyzing
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