5,623 research outputs found
Inter-cluster Filaments of Galaxies Programme: Abundance and Distribution of Filaments in the 2dFGRS Catalogue
Filaments of galaxies are known to stretch between galaxy clusters at all
redshifts in a complex manner. In this Letter, we present an analysis of the
frequency and distribution of inter-cluster galaxy filaments selected from the
2dF Galaxy Redshift Survey. Out of 805 cluster-cluster pairs, we find at least
40 per cent have bone-fide filaments. We introduce a filament classification
scheme and cast the filaments into several types according to their visual
morphology: straight (lying on the cluster-cluster axis; 37 per cent), warped
or curved (lying off the cluster-cluster axis; 33 per cent), sheets (planar
configurations of galaxies; 3 per cent), uniform (1 per cent) and irregular (26
per cent). We find that straight filaments are more likely to reside between
close cluster pairs and they become more curved with increasing cluster
separation. This curving is toward a larger mass concentration in general. We
also show that the more massive a cluster is, the more likely it is to have a
larger number of filaments. Our results are found to be consistent with a
Lambda cold dark matter cosmology.Comment: 6 pages, 3 figures, accepted for publication in MNRAS letter
Informal Caring and Labour Market Outcomes Within England and Wales
This paper focuses on the links between informal care provision and labour market activity at the sub-national level. Within-country analysis of this issue has been very limited to date despite the wide regional variations in informal care provision that often exist. This issue is important in the context of policy decisions in Wales and other parts of the UK because of relatively high levels of informal caring in certain areas, especially in the South Wales Valleys. In particular, given that these areas typically have the lowest economic activity and employment rates, labour market differences can be exacerbated by the provision of informal caring by people of working age. Despite the wide variations in informal care provision, it is found that labour market outcomes do not differ markedly by different care categories across spatial areas within England and Wales. However, the analysis reveals that labour market outcomes for males as well as females are heavily influenced for those who provide high levels of caring, especially in the South Wales Valleys. For example, the largest impact of caring on the probability of not working for males and for part-time work for females is seen in this area.labour market outcomes, informal care provision, area variations
Go West? Assessing the willingness to move from Central and Eastern European Countries
This paper uses cross national survey data to examine the willingness to move of residents from several Central and Eastern European Countries (CEECs). This is of particular relevance given that some of these countries will be part of the forthcoming enlargement of the EU, and hence individuals from these countries will eventually be allowed to move freely between member states. Whereas most previous studies have used aggregate data to forecast flows from the East following enlargement, the emphasis in this paper is on the reasons why individuals may not want to move and it is argued that these factors may outweigh the possible high rewards in the West for many individuals. It is found that although individuals in some of the CEECs display a relatively high willingness to move, overall, the willingness to move country is lower in the CEECs than it is in the EU. Furthermore, the availability of microdata enables the characteristics of those individuals who are most willing to move to be established and the evidence suggests that the most qualified individuals have the highest willingness to move.Migration, EU enlargement, Labour immobility
Operating limits for acoustic measurement of rolling bearing oil film thickness
An ultrasonic pulse striking a thin layer of liquid trapped between solid bodies will be partially reflected. The proportion reflected is a function of the layer stiffness, which in turn depends on the film thickness and its bulk modulus. In this work, measurements of reflection have been used to determine the thickness of oil films in elastohydrodynamic lubricated (EHL) contacts. A very thin liquid layer behaves like a spring when struck by an ultrasonic pulse. A simple quasi-static spring model can be used to determine the proportion of the ultrasonic waves reflected. Experiments have been performed on a model EHL contact between a ball and a flat surface. A transducer is mounted above the contact such that the ultrasonic wave is focused onto the oil film. The reflected signals are captured and passed to a PC for processing. Fourier analysis gives the reflection spectrum that is then used to determine the stiffness of the liquid layer and hence its thickness. In further testing, an ultrasonic transducer has been mounted in the housing of a deep-groove ball bearing to measure the film generated at the outer raceway as each ball passes. Results from both the ball-flat and ball bearing measurements agree well with steady-state theoretical EHL predictions. The limits of the measuring technique, in terms of the measurable rolling bearing size and operating parameters, have been investigated
Welfare Participation by Immigrants in the UK
Welfare participation is an important indicator of how successfully immigrants perform in the host country. This paper examines this issue for the UK, which has experienced a large growth in its immigrant flows and population levels in recent years, especially following EU enlargement in 2004. The analysis focuses in particular on the types of benefits that immigrants tend to claim as well as examining differences by area of origin. It also examines the factors that determine social benefit claims, including an investigation of the impact of education ethnicity and years since migration. Social welfare claims vary considerably by immigrant group as well as by the type of benefit claimed in the UK. There is also some variation by gender within the migrant groups
2MASS Galaxies in the Fornax Cluster Spectroscopic Survey
The Fornax Cluster Spectroscopic Survey (FCSS) is an all-object survey of a
region around the Fornax Cluster of galaxies undertaken using the 2dF
multi-object spectrograph on the Anglo-Australian Telescope. Its aim was to
obtain spectra for a complete sample of all objects with 16.5 < b_j < 19.7
irrespective of their morphology (i.e. including `stars', `galaxies' and
`merged' images). We explore the extent to which (nearby) cluster galaxies are
present in 2MASS. We consider the reasons for the omission of 2MASS galaxies
from the FCSS and vice versa. We consider the intersection (2.9 square degrees
on the sky) of our data set with the infra-red 2 Micron All-Sky Survey (2MASS),
using both the 2MASS Extended Source Catalogue (XSC) and the Point Source
Catalogue (PSC). We match all the XSC objects to FCSS counterparts by position
and also extract a sample of galaxies, selected by their FCSS redshifts, from
the PSC. We confirm that all 114 XSC objects in the overlap sample are
galaxies, on the basis of their FCSS velocities. A total of 23 Fornax Cluster
galaxies appear in the matched data, while, as expected, the remainder of the
sample lie at redshifts out to z = 0.2 (the spectra show that 61% are early
type galaxies, 18% are intermediate types and 21% are strongly star
forming).The PSC sample turns out to contain twice as many galaxies as does the
XSC. However, only one of these 225 galaxies is a (dwarf) cluster member. On
the other hand, galaxies which are unresolved in the 2MASS data (though almost
all are resolved in the optical) amount to 71% of the non-cluster galaxies with
2MASS detections and have redshifts out to z=0.32.Comment: 5 pages, accepted by A&A, resubmitted due to missing reference
Galaxy threshing and the formation of ultra-compact dwarf galaxies
Recent spectroscopic and morphological observational studies of galaxies
around NGC 1399 in the Fornax Cluster (Drinkwater et al. 2000b) have discovered
several `ultra-compact dwarf' galaxies with intrinsic sizes of 100 pc
and absolute band magnitudes ranging from -13 to -11 mag. In order to
elucidate the origin of these enigmatic objects, we perform numerical
simulations on the dynamical evolution of nucleated dwarf galaxies orbiting NGC
1399 and suffering from its strong tidal gravitational field. Adopting a
plausible scaling relation for dwarf galaxies, we find that the outer stellar
components of a nucleated dwarf are totally removed. This is due to them being
tidally stripped over the course of several passages past the central region of
NGC 1399. The nucleus, however, manages to survive. We also find that the size
and luminosity of the remnant are similar to those observed for ultra-compact
dwarf galaxies, if the simulated precursor nucleated dwarf has a mass of
. These results suggest that ultra-compact dwarf galaxies
could have previously been more luminous dwarf spheroidal or elliptical
galaxies with rather compact nuclei.Comment: 9 pages 4 figures,2001, ApJL, 552, 10
Metamaterials: -classical dynamic homogenization
Metamaterials are artificial composite structures designed for controlling
waves or fields, and exhibit interaction phenomena that are unexpected on the
basis of their chemical constituents. These phenomena are encoded in effective
material parameters that can be electronic, magnetic, acoustic, or elastic, and
must adequately represent the wave interaction behaviour in the composite
within desired frequency ranges. In some cases -- for example, the low
frequency regime -- there exist various efficient ways by which effective
material parameters for wave propagation in metamaterials may be found.
However, the general problem of predicting frequency-dependent dynamic
effective constants has remained unsolved. Here, we obtain novel mathematical
expressions for the effective parameters of two-dimensional metamaterial
systems valid at higher frequencies and wavelengths than previously possible.
By way of an example, random configurations of cylindrical scatterers are
considered, in various physical contexts: sound waves in a compressible fluid,
anti-plane elastic waves, and electromagnetic waves. Our results point towards
a paradigm shift in our understanding of these effective properties, and
metamaterial designs with functionalities beyond the low-frequency regime are
now open for innovation.Comment: 14 pages (including 4 figures and 1 table) in New Journal of Physics,
201
Fornax compact object survey FCOS: On the nature of Ultra Compact Dwarf galaxies
The results of the Fornax Compact Object Survey (FCOS) are presented. The
FCOS aims at investigating the nature of the Ultra Compact Dwarf galaxies
(UCDs) recently discovered in the center of the Fornax cluster (Drinkwater et
al. 2000). 280 unresolved objects in the magnitude space covering UCDs and
bright globular clusters (18<V<21 mag) were observed spectroscopically. 54 new
Fornax members were discovered, plus five of the seven already known UCDs.
Their distribution in radial velocity, colour, magnitude and space was
investigated. It is found that bright compact objects (V<20 or M_V<-11.4 mag),
including the UCDs, have a higher mean velocity than faint compact objects
(V>20 mag) at 96% confidence. The mean velocity of the bright compact objects
is consistent with that of the dwarf galaxy population in Fornax, but
inconsistent with that of NGC 1399's globular cluster system at 93.5%
confidence. The compact objects follow a colour magnitude relation with a slope
very similar to that of normal dEs, but shifted about 0.2 mag redwards. The
magnitude distribution of compact objects shows a fluent transition between
UCDs and GCs with an overpopulation of 8 +/- 4 objects for V<20 mag with
respect to the extrapolation of NGC 1399's GC luminosity function. The spatial
distribution of bright compact objects is in comparison to the faint ones more
extended at 88% confidence. All our findings are consistent with the threshing
scenario (Bekki et al. 2003), suggesting that a substantial fraction of compact
Fornax members brighter than V~20 mag could be created by threshing dE,Ns.
Fainter than V~20 mag, the majority of the objects seem to be genuine GCs. Our
results are also consistent with merged stellar super-clusters (Fellhauer &
Kroupa 2002) as an alternative explanation for the bright compact objects.Comment: 15 pages, 11 figures, accepted for publication in A&
Some aspects of electro-chemical grid-marking
Introduction
The value of fine grids, electromarked (1) on to metal sheets
before pressing, so that the type and magnitude of the strain developed
in the critical region of the pressing can be assessed, is undisputed.
Keeler (2), Meyer and Newby (3), and Goodwin (4), have all discussed
practical applications of this technique and Palmer (5) has reviewed
the field and introduced the concept of a relative safety factor (MSF).
However it may be useful to see what this 'mark' consists of, how the
marking affects the subsequent metal performance, what the limitations
of the process are and other peripherical issues. It is these aspects
of the process which is the concern of this paper
- âŠ