587 research outputs found
Overcoming the Challenge of a Visible Facial Difference at Interview: Pre-Familiarisation can be Effective
Previous studies have shown that a candidate with a visible facial difference (VFD) may experience discrimination during recruitment. This study investigated whether a VFD imposes a disadvantage in a simulated job interview and whether pre-familiarisation to the candidate’s appearance can reduce the disadvantage. Participants (n = 128) observed a video of a job interview in one of three conditions: a short audio pre-familiarisation and no VFD at interview (Control); audio pre-familiarisation and VFD at interview (Unexpected); and video pre-familiarisation then VFD at interview (Familiarised). Participants subsequently evaluated the candidate on personal and professional traits. Results revealed higher evaluations in the Unexpected compared to Control condition for Professional Skills, Emotional Stability, and especially strongly for Warmth, attributed to positive discrimination. In the Familiarised condition, the evaluations lay between Control and Unexpected, the only significant difference being lower Warmth in Familiarised than Unexpected. Of particular interest, different traits were associated with the key variable of Role Suitability in the three conditions: in Control, Role Suitability correlated with the job-relevant traits of Emotional Stability and Professional Skills; in Unexpected, the association with Professional Skills was weaker, and there was a significant association with Warmth; in Familiarised, there were no significant associations. In the Familiarised condition, compared to Unexpected, participants found the candidate’s appearance less distracting, and believed the pre-familiarisation would help the interviewer. These results were interpreted as suggesting that a VFD may harm the candidate’s chances of being evaluated fairly on their merits, but this disadvantage may be partially overcome by pre-familiarisation
Ring Star Formation Rates in Barred and Nonbarred Galaxies
Nonbarred ringed galaxies are relatively normal galaxies showing bright rings
of star formation in spite of lacking a strong bar. This morphology is
interesting because it is generally accepted that a typical ring forms when
material collects near a resonance, set up by the pattern speed of a bar or
bar-like perturbation. Our goal in this paper is to examine whether the ring
star formation properties are related to the non-axisymmetric gravity potential
in general. For this purpose, we obtained H{\alpha} emission line images and
calculated the line fluxes and star formation rates (SFRs) for 16 nonbarred SA
galaxies and four weakly barred SAB galaxies with rings. For comparison, we
combine our observations with a re-analysis of previously published data on
five SA, seven SAB, and 15 SB galaxies with rings, three of which are
duplicates from our sample. With these data, we examine what role a bar may
play in the star formation process in rings. Compared to barred ringed
galaxies, we find that the inner ring SFRs and H{\alpha}+[N ii] equivalent
widths in nonbarred ringed galaxies show a similar range and trend with
absolute blue magnitude, revised Hubble type, and other parameters. On the
whole, the star formation properties of inner rings, excluding the distribution
of H ii regions, are independent of the ring shapes and the bar strength in our
small samples. We confirm that the deprojected axis ratios of inner rings
correlate with maximum relative gravitational force Q_g; however, if we
consider all rings, a better correlation is found when local bar forcing at the
radius of the ring, Q_r, is used. Individual cases are described and other
correlations are discussed. By studying the physical properties of these
galaxies, we hope to gain a better understanding of their placement in the
scheme of the Hubble sequence and how they formed rings without the driving
force of a bar.Comment: 55 pages; 21 figures and 9 tables. Article has been accepted for
publication in the Astronomical Journa
Trace element incorporation in silicate melts and glasses at high pressure
Trace elements are highly fractionated during large-scale melting associated with
planetary differentiation events. The resulting partition coefficients are used
to constrain a range of geological processes and are known to be influenced
by pressure, temperature, and compositional changes in crystalline structures.
Although recent studies have shown that melt compositional changes affect the
partitioning of trace elements, the degree to which these ratios are influenced
by alterations in the melt structure, especially with increasing pressure, is
poorly constrained due to the difficulty of collecting structural information on
bonding environments in situ. A basic understanding of how these elements
are incorporated in silicate melts is critical to interpreting early planetary
differentiation and crust forming events. This thesis presents results from both
x-ray diffraction and absorption techniques on trace element (Y, Zr, Lu and Nd)
incorporation in silicate melt structures. The structure of two rare Earth element
doped model end member silicate liquids, a highly polymerised haplogranite (Si-
Al-Na-K-O) and a less polymerised anorthite-diopside (Si-Al-Mg-Ca-O), have
been studied. The results are the first to identify trace rare Earth element (REE)
incorporation in silicate melts at high pressure using x-ray diffraction techniques.
The local melt structure around Y and Zr in a highly polymerised haplogranite
has been studied using x-ray absorption spectroscopy up to 8GPa and 1650 K.
Both elements appear to adopt 8-fold coordination within the melt structure
with no variation over the pressure range studied. This was also found for the Lu
bonding environment in the same composition where the coordination number of
Lu-O was found to be 8, with a bond distance rLu-O = 2:36A in the haplogranite
melt. At low pressures, < 5GPa, the bonding environment of Lu-O was found
to be dependent on composition with coordination decreasing to CNLu-O = 6
and rLu-O = 2:29A in the anorthite-diopside melt. This compositional variance
in coordination number at low pressure is consistent with observations made for
Y-O in glasses at ambient conditions and is coincident with a dramatic increase
in the partition coefficients previously observed for rare Earth elements (REE)
with increasing melt polymerisation. However, an abrupt change in both Lu-O
coordination and bond distance is observed at 5GPa in the anorthite-diopside
melt, with CNLu-O increasing from 6 to 8-fold and rLu-O from 2.29 to 2.39A.
This occurs over a similar pressure range where a reduction in the reported heavy
REE partition coefficients is observed.
X-ray diffraction experiments up to 60GPa and 2000K have also been performed
on the incorporation of the larger light REE, Nd, in basaltic-like melts.
The results presented show that incorporation within the anorthite-diopside
composition is dependent on the size of the REE. Nd-O initially shows the
same 6-fold coordination as Lu-O at ambient conditions, although the change
to 8-fold coordination appears to occur at considerably lower pressure between
1-2GPa. Coordination change in both cases can be attributed to collapse of
the silicate network and an increase in the average number of available 'crystal
like' sites in the liquid, with ionic radius of the REE controlling at which
pressure the preference for these sites in the melt occurs. Published mineral-melt
partition coefficients for Nd, with major mineral phases such as garnet, show
very little variation with pressure, in contrast to Lu. The difference in structural
incorporation of Lu and Nd in the melts presented in this thesis could explain
this partitioning behaviour.
Overall this thesis highlights that important structural changes of the trace
element bonding environment in silicate melts occur with both compositional
variation and pressure. Melt structural changes with pressure cannot be
neglected in predictive models of trace element behaviour, and using a single
melt term to normalise the effects of melt on trace element partitioning will not
accurately predict partitioning behaviour at depth during magma formation or
differentiation
Experimental Studies of the Interaction of Radiatively Cooled Supersonic Plasma Jets with Ambient Plasma
We present the design, development and characterisation of an experimental platform for studying astrophysically relevant plasma jet interactions with ambient plasma. Jet and ambient plasmas are formed during the z-pinch discharge of a 1.4MA, 240ns current pulse delivered by Imperial College London's MAGPIE generator. Jets are of centimetre length and microsecond lifetime but have sufficiently large Reynolds and Péclet numbers (> 10,000) to permit well-scaled comparison with non-magnetised astrophysical jets, including the bipolar outflows of protostars. Jet densities are of order 10e19 particles per cubic centimetre, and density ratios (jet density/ambient density) between 1 and 10, are demonstrated. Jets are formed by ablation of micrometer thickness aluminium (Al) or tungsten (W) wires arranged in the conical or radial wire array z-pinch geometries. Ambient plasmas are formed during the same current pulse by ablation of wires in the cylindrical wire array geometry, or the surface of a 14 micrometre thickness, 40mm diameter aluminium foil. Leading shock features launched by conical wire array jet material into foil-driven plasmas demonstrate effective adiabatic indices of 1.4 and 1.2 for Al/Al and W/Al interactions respectively. Radial wire arrays are observed to drive higher Mach number interactions than those of conical wire arrays, with upstream Mach numbers M > 3.5 and M > 1.7 respectively. Instability growth is observed during radial wire array jet experiments along the leading shocks and jet edges, on timescales typical of Rayleigh-Taylor and Kelvin-Helmholtz instabilities under our experimental conditions. This work complements and extends current numerical modelling of non-magnetised astrophysical jet propagation, and offers a body of controlled, repeatable experimental data for future code validation work.Open Acces
Molecular cytotaxonomy of primates by chromosomal in situ suppression hybridization
A new strategy for analyzing chromosomal evolution in primates is presented using chromosomal in situ suppression (CISS) hybridization. Biotin-labeled DNA libraries from flow-sorted human chromosomes are hybridized to chromosome preparations of catarrhines, platyrrhines, and prosimians. By this approach rearrangements of chromosomes that occurred during hominoid evolution are visualized directly at the level of DNA sequences, even in primate species with pronounced chromosomal shuffles
Numerical study of jets produced by conical wire arrays on the Magpie pulsed power generator
The aim of this work is to model the jets produced by conical wire arrays on
the MAGPIE generator, and to design and test new setups to strengthen the link
between laboratory and astrophysical jets. We performed the modelling with
direct three-dimensional magneto-hydro-dynamic numerical simulations using the
code GORGON. We applied our code to the typical MAGPIE setup and we
successfully reproduced the experiments. We found that a minimum resolution of
approximately 100 is required to retrieve the unstable character of the jet. We
investigated the effect of changing the number of wires and found that arrays
with less wires produce more unstable jets, and that this effect has magnetic
origin. Finally, we studied the behaviour of the conical array together with a
conical shield on top of it to reduce the presence of unwanted low density
plasma flows. The resulting jet is shorter and less dense.Comment: Accepted for publication in Astrophysics & Space Science. HEDLA 2010
conference procedings. Final pubblication will be available on Springe
Concurrence of Ring 21 and Trisomy 21 in Children of Normal Parents
We present a case of two siblings with different chromosome 21 abnormalities that are both de novo [r(21)/i(21p13) mosaicism and rob(14;21)]. Molecular studies using polymorphic markers have shown that these two aberrations had a common maternal origin. However, the parents were cytogenetically and phenotypically normal. This unusual association has not been reported and is considered to be a unique case that should be addressed
Near-IR Atlas of S0-Sa galaxies (NIRS0S)
An atlas of Ks-band images of 206 early-type galaxies is presented, including
160 S0-S0/a galaxies, 12 ellipticals, and 33 Sa galaxies. A majority of the
Atlas galaxies belong to a magnitude-limited (mB<12.5 mag) sample of 185 NIRS0S
(Near-IR S0 galaxy Survey) galaxies. To assure that mis-classified S0s are not
omitted, 25 ellipticals from RC3 classified as S0s in the Carnegie Atlas were
included in the sample. The images are 2-3 mag deeper than 2MASS images. Both
visual and photometric classifications are made. Special attention is paid to
the classification of lenses, coded in a systematic manner. A new lens-type,
called a 'barlens', is introduced. Also, boxy/peanut/x-shaped structures are
identified in many barred galaxies, even-though the galaxies are not seen in
edge-on view, indicating that vertical thickening is not enough to explain
them. Multiple lenses appear in 25% of the Atlas galaxies, which is a challenge
to the hierarchical evolutionary picture of galaxies. Such models need to
explain how the lenses were formed and survived in multiple merger events that
galaxies may have suffered during their lifetimes. Following the early
suggestion by van den Bergh, candidates of S0c galaxies are shown, which
galaxies are expected to be former Sc-type spirals stripped out of gas.Comment: 67 pages (include 16 figures and 6 tables). Accepted to MNRAS 2011
June 1
Lutetium incorporation in magmas at depth:changes in melt local environment and the influence on partitioning behaviour
International audienceThe structure of two Lu doped (4000 ppm) model end member silicate liquids, a highly polymerised haplogranite (Si-Al-Na-K-O) and a less polymerised anorthite-diopside (Si-Al-Mg-Ca-O), have been studied up to 8 GPa using in situ x-ray diffraction techniques. The results are the first to identify trace rare Earth element incorporation in silicate melts at high pressure. At pressures below 5 GPa, the bonding environment of Lu-O was found to be dependent on composition with coordination number CN Lu−O = 8 and bond distance r Lu−O = 2.36Å36Å in the haplogranite melt, decreasing to CN Lu−O = 6 and r Lu−O = 2.29Å29Å in the anorthite-diopside melt. This compositional variance in coordination number at low pressure is consistent with observations made for Y-O in glasses at ambient conditions and is coincident with a dramatic increase in the partition coefficients previously observed for rare Earth elements with increasing melt polymerisation. With increasing pressure we find that CN Lu−O and r Lu−O remain constant in the haplo-granite melt. However, an abrupt change in both Lu-O coordination and bond distance is observed at 5 GPa in the anorthite-diopside melt, with CN Lu−O increasing from 6 to 8-fold and r Lu−O from 2.29 to 2.39Å39Å. This occurs over a similar pressure range where a change in the P-dependence in the reported rare Earth element partition coefficients is observed for garnet-, clinopyroxene-, and olivine-melt systems. This work shows that standard models for predicting trace elements at depth must incorporate the effect of pressure-induced structural transformations in the melt in order to realistically predict partitioning behaviour
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