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The effect of pitch span on intonational plateaux
Previous research has indicated that the H (high) of a nuclear accent may be realized as a flat stretch of contour rather than as a single turning point. Both the duration of this plateau and its alignment within the accented syllable are affected by the segmental and prosodic structure of the utterance. The present work investigates whether a non-structural variable, namely pitch span, also affects the realization of the plateau. Speakers replicated all-sonorant utterances in different pitch spans. Results show that both the duration and alignment of the plateau vary with pitch span but in ways different from the way they vary with prosodic structure. Importantly, results also indicate that, when using a proportional measure of alignment, the end of the plateau is anchored within the syllable for each speaker and may be a marker of linguistic structure
Generating Macroscopic Superpositions with Interacting Bose-Einstein Condensates: Multi-Mode Speed-Ups and Speed Limits
We theoretically investigate the effect of multi-mode dynamics on the
creation of macroscopic superposition states (spin-cat states) in Bose-Einstein
condensates via one-axis twisting. A two-component Bose-Einstein condensate
naturally realises an effective one-axis twisting interaction, under which an
initially separable state will evolve toward a spin-cat state. However, the
large evolution times necessary to realise these states is beyond the scope of
current experiments. This evolution time is proportional to the degree of
asymmetry in the relative scattering lengths of the system, which results in
the following trade-off; faster evolution times are associated with an increase
in multi-mode dynamics, and we find that generally multi-mode dynamics reduce
the degree of entanglement present in the final state. However, we find that
highly entangled cat-like states are still possible in the presence of
significant multi-mode dynamics, and that these dynamics impose a speed-limit
on the evolution such states
Glycosylphosphatidylinositols: More than just an anchor?
There is increasing interest in the role of glycosylphosphatidylinositol (GPI) anchors that attach some proteins to cell membranes. Far from being biologically inert, GPIs influence the targeting, intracellular trafficking and function of the attached protein. Our recent paper demonstrated the role of sialic acid on the GPI of the cellular prion protein (PrPC). The âprion diseasesâ arise following the conversion of PrPC to a disease-associated isoform called PrPSc or âprionâ. Our paper showed that desialylated PrPC inhibited PrPSc formation. Aggregated PrPSc creates a signaling platform in the cell membrane incorporating and activating cytoplasmic phospholipase A2 (cPLA2), an enzyme that regulates PrPC trafficking and hence PrPSc formation. The presence of desialylated PrPC caused the dissociation of cPLA2 from PrP-containing platforms, reduced the activation of cPLA2 and inhibited PrPSc production. We concluded that sialic acid contained within the GPI attached to PrPC modifies local membrane microenvironments that are important in PrP-mediated cell signaling and PrPSc formation
Finding Young Stellar Populations in Elliptical Galaxies from Independent Components of Optical Spectra
Elliptical galaxies are believed to consist of a single population of old
stars formed together at an early epoch in the Universe, yet recent analyses of
galaxy spectra seem to indicate the presence of significant younger populations
of stars in them. The detailed physical modelling of such populations is
computationally expensive, inhibiting the detailed analysis of the several
million galaxy spectra becoming available over the next few years. Here we
present a data mining application aimed at decomposing the spectra of
elliptical galaxies into several coeval stellar populations, without the use of
detailed physical models. This is achieved by performing a linear independent
basis transformation that essentially decouples the initial problem of joint
processing of a set of correlated spectral measurements into that of the
independent processing of a small set of prototypical spectra. Two methods are
investigated: (1) A fast projection approach is derived by exploiting the
correlation structure of neighboring wavelength bins within the spectral data.
(2) A factorisation method that takes advantage of the positivity of the
spectra is also investigated. The preliminary results show that typical
features observed in stellar population spectra of different evolutionary
histories can be convincingly disentangled by these methods, despite the
absence of input physics. The success of this basis transformation analysis in
recovering physically interpretable representations indicates that this
technique is a potentially powerful tool for astronomical data mining.Comment: 12 Pages, 7 figures; accepted in SIAM 2005 International Conference
on Data Mining, Newport Beach, CA, April 200
Relative Income, Redistribution and Well-being
In a model with heterogeneous workers and both intensive and extensive margins of employment, we consider two systems of redistribution: a universal basic income, and a categorical unemployment benefit. Well-being depends on own-consumption relative to average employed workersâ consumption, and concern for relativity is a parameter that affects model outcomes. While labour supply incurs positive marginal disutility, we allow negative welfare effects of unemployment. We also compare Rawlsian and utilitarian welfare in general equilibrium under the polar opposite transfer systems, with varying concern for relativity. Basic income Pareto dominates categorical benefits with moderate concern for relativity in both cases.relative income, redistribution, basic income, unemployment benefits, happiness, well-being
The Sun, stellar-population models, and the age estimation of high-redshift galaxies
Given sufficiently deep optical spectroscopy, the age estimation of
high-redshif t () galaxies has been claimed to be a relatively robust
process (e.g. Dunlop et al. 1996) due to the fact that, for ages Gyr, the
near-ultraviolet light of a stellar population is expected to be dominated by
`well-understood' main-sequence (MS) stars. Recently, however, the reliability
of this process has been called into question by Yi et al (2000), who claim to
have developed models in which the spectrum produced by the main sequence
reddens much more rapidly than in the models of Jimenez et al (2000a), leading
to much younger age estimates for the reddest known high-redshift ellipticals.
In support of their revised age estimates, Yi et al cite the fact that their
models can reproduce the spectrum of the Sun at an age of 5 Gyr, whereas the
solar spectrum is not reproduced by the Jimenez et al models until
Gyr. Here we confirm this discrepancy, but point out that this is in fact a
{\it strength} of the Jimenez et al models and indicative of some flaw in the
models of Yi et al (which, in effect, imply that the Sun will turn into a red
giant any minute now). We have also explored the models of Worthey (1994)
(which are known to differ greatly from those of Jimenez et al in the treatment
of post-MS evolution) and find that the main-sequence component of Worthey's
models also cannot reproduce the solar spectrum until an age of 9-10 Gyr. We
conclude that either the models of Yi et al are not as main-sequence dominated
at 4-5 Gyr as claimed, or that the stellar evolutionary timescale in these
models is in error by a factor possibly as high as two. (abridged)Comment: Submitted to MNRAS, final versio
A New Feature in the Spectrum of the Superluminous LMC Supergiant HDE 269896
We have found strong selective emission of the N II 5000A complex in the
spectrum of the LMC hypergiant HDE 269896, ON9.7 Ia. Since this object also
has anomalously strong He II 4686 emission for its spectral type, an
unusually wide range of ionization in its extended atmosphere is indicated. The
published model of this spectrum does not reproduce these emission features,
but we show that increased nitrogen and helium abundances, together with small
changes in other model parameters, can do so. The morphological and possible
evolutionary relationships of HDE 269896, as illuminated by the new spectral
features, to other denizens of the OB Zoo are discussed. This object may be in
an immediate pre-WNVL (Very Late WN) state, which is in turn the quiescent
state of at least some Luminous Blue Variables.
More generally, the N II spectrum in HDE 269896 provides a striking
demonstration of the occurrence of two distinctly different kinds of line
behavior in O-type spectra: normal absorption lines that develop P Cygni
profiles at high wind densities, and selective emission lines from the same
ions that do not. Further analysis of these features will advance understanding
of both atomic physics and extreme stellar atmospheres.Comment: 12 pages, 2 tables, 4 figures (quality downgraded due to size
constraints); to appear in PASP January 200
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