766 research outputs found
Star formation and the interstellar medium in z>6 UV-luminous Lyman-break galaxies
We present Atacama Large Millimeter Array (ALMA) detections of atomic carbon
line and dust continuum emission in two UV-luminous galaxies at redshift 6. The
far-infrared (FIR) luminosities of these galaxies are substantially lower than
similar starbursts at later cosmic epochs, indicating an evolution in the dust
properties with redshift, in agreement with the evolution seen in ultraviolet
(UV) attenuation by dust. The [CII] to FIR ratios are found to be higher than
at low redshift showing that [CII] should be readily detectable by ALMA within
the reionization epoch. One of the two galaxies shows a complex merger nature
with the less massive component dominating the UV emission and the more massive
component dominating the FIR line and continuum. Using the interstellar atomic
carbon line to derive the systemic redshifts we investigate the velocity of
Lyman alpha emission emerging from high-z galaxies. In contrast to previous
work, we find no evidence for decreasing Lyman alpha velocity shifts at
high-redshift. We observe an increase in velocity shifts from z2 to
z6, consistent with the effects of increased IGM absorption.Comment: 10 pages, 9 figures, submitted to ApJ, revised after referees
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Using a damper amplification factor to increase energy dissipation in structures
AbstractFluid dampers are an important tool for dissipating unwanted vibrations in a range of engineering structures. This paper examines the effects of amplifying the displacements transferred to a non-linear damper, to increase the effectiveness of the damper in a range of situations commonly encountered in civil engineering structures. These include, (i) the ability to āfine tuneā the required damping for a particular size damper, (ii) the ability to have a set of the same size dampers, but with different amplification factors to achieve a specific damping task, and (iii) to increase the sensitivity of the damper to small movements which effectively extends the range over which the damper works. Through numerical simulations and experimental tests conducted on a non-linear damper, we quantify the potential advantages of adding an amplification factor and the range of parameters where the benefit to this device is significant. The example of a two-storey structure is used as a test case and real-time dynamic substructuring tests are used to assess the complete system performance using a range of different amplification factors. The results show that the structural performance is most improved for frequencies close to resonance and that the amplification factor has an effective limit that for the case considered in this study is of approximately 3. The effects of the mechanism compliance are also assessed
Supporting brace sizing in structures with added linear viscous fluid dampers: A filter design solution
Viscous fluid dampers have proved to be effective in suppressing unwanted vibrations in a range of engineering structures. When dampers are fitted in a structure, a brace is typically used to attach them to the main structure. The stiffness of this brace can significantly alter the effectiveness of the damper, and in structures with multiple dampers, this can be a complex scenario to model. In this paper, we demonstrate that the effects of the brace compliance on the damper performance can be modelled by way of a first-order filter. We use this result to formulate a procedure that calculates the stiffness required by the supporting brace to provide a specified effectiveness of the damping action. The proposed procedure assumes that viscous dampers have been sized in a previous design step based on any optimal methodology in which, as is usually the case, the presence of supporting braces and their dynamic effects were neglected. Firstly considering a one degree-of-freedom system, we show that the proposed method ensures a desired level of damper efficiency for all frequencies within a selected bandwidth. Then the analysis is extended to the case of multi-degree-of-freedom systems to show that the design criteria can be applied in a straightforward and successful manner to more complex structures
Work and society: Places, spaces and identities
The table of contents and introduction are included with kind permission of University of Chester Press.The original theoretical and empirical studies in this new edited volume, Work and Society: Places, Spaces and Identities, present a re-imagining of what work is, how it is undertaken, and the impact of work on people who engage in it. While traditional examinations of work are synonymous with discussions of labour markets, organisational functions and industrial relations, the eight contributions published here for the first time extend our conceptualisation of work to take in less commonly scrutinised activities such as care-giving, soldiering, gambling and career criminality. This intriguing approach opens up space for an exciting reconsideration of the relationships between work and society, focussing on illegitimate and unvalued occupations, the places where personal and professional identities intersect in risky or rewarding ways, and the ideological imperative on all of us ā no matter our employment status ā to perform as resilient, productive neoliberal subjects with the capacity for work. This innovative, interdisciplinary volume brings together established and new voices in the fields of sociology, criminology, victimology and political economy to present an accessible intervention in current debates about work in the twenty-first century
Galaxy Formation Through Filamentary Accretion at z=6.1
We present ALMA observations of the dust continuum and [C II] 158um line
emission from the z=6.0695 Lyman Break Galaxy WMH5. These observations at 0.3"
spatial resolution show a compact (~3kpc) main galaxy in dust and [C II]
emission, with a 'tail' of emission extending to the east by about 5kpc (in
projection). The [C II] tail is comprised predominantly of two distinct
sub-components in velocity, separated from the core by ~100 and 250km/s, with
narrow intrinsic widths of about 80km/s, which we call 'sub-galaxies'. The
sub-galaxies themselves are extended east-west by about 3kpc in individual
channel images. The [C II] tail joins smoothly into the main galaxy velocity
field. The [C II] line to continuum ratios are comparable for the main and
sub-galaxy positions, within a factor 2. In addition, these ratios are
comparable to z~5.5 LBGs. We conjecture that the WMH5 system represents the
early formation of a galaxy through the accretion of smaller satellite
galaxies, embedded in a smoother gas distribution, along a possibly filamentary
structure. The results are consistent with current cosmological simulations of
early galaxy formation, and support the idea of very early enrichment with dust
and heavy elements of the accreting material.Comment: 10 pages, 9 figures, Accepted for publication in Ap
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