On the role of pressure anisotropy for relativistic stars admitting conformal motion

We investigate the spacetime of anisotropic stars admitting conformal motion. The Einstein field equations are solved using different ansatz of the surface tension. In this investigation, we study two cases in details with the anisotropy as: [1] $p_t = n p_r$ [2] $p_t - p_r = \frac{1}{8 \pi}(\frac{c_1}{r^2} + c_2)$ where, n, $c_1$ and $c_2$ are arbitrary constants. The solutions yield expressions of the physical quantities like pressure gradients and the mass.Comment: 21 pages, accepted for publication in 'Astrophysics and Space Science

Galactic Gamma Halo by Heavy Neutrino annihilations?

The diffused gamma halo around our Galaxy recently discovered by EGRET could be produced by annihilations of relic neutrinos N (of fourth generation), whose mass is within a narrow range (Mz /2 < M < Mz). Neutrino annihilations in the halo may lead to either ultrarelativistic electron pairs whose inverse Compton Scattering on infrared or optical galactic photons could be the source of the observed GeV gamma rays, or to prompt 100 MeV- 1 GeV photons (due to neutral pion secondaries) born by N - anti N --> Z--> quark pairs reactions. The consequent gamma flux (10 ^(-7)- 10^(-6) cm ^(-2) s^(-1) sr^(-1)) is well comparable to the EGRET observed one and it is also compatible with the narrow window of neutrino mass : 45 GeV < M < 50 GeV recently required to explain the underground DAMA signals. The presence of heavy neutrinos of fourth generation do not contribute much to solve the dark matter problem of the Universe, but it may be easily detectable by outcoming LEP II data.Comment: 16 pages, Latex text,in press in Astroparticle Physics 199

Supersymmetric dark matter in M31: can one see neutralino annihilation with CELESTE?

It is widely believed that dark matter exists within galaxies and clusters of galaxies. Under the assumption that this dark matter is composed of the lightest, stable supersymmetric particle, assumed to be the neutralino, the feasibility of its indirect detection via observations of a diffuse gamma-ray signal due to neutralino annihilations within M31 is examined. To this end, first the dark matter halo of the close spiral galaxy M31 is modeled from observations, then the resultant gamma-ray flux is estimated within supersymmetric model configurations. We conclude that under favorable conditions such as the rapid accretion of neutralinos on the central black hole in M31 and/or the presence of many clumps inside its halo with $r^{-3/2}$ inner profiles, a neutralino annihilation gamma-ray signal is marginally detectable by the ongoing collaboration CELESTE.Comment: Latex, 32 pages, 12 figures, 5 table

What Paves the Way to Conventional Language? The Predictive Value of Babble, Pointing, and Socioeconomic Status

A child's first words mark the emergence of a uniquely human ability. Theories of the developmental steps that pave the way for word production have proposed that either vocal or gestural precursors are key. These accounts were tested by assessing the developmental synchrony in the onset of babbling, pointing, and word production for 46 infants observed monthly between the ages of 9 and 18 months. Babbling and pointing did not develop in tight synchrony and babble onset alone predicted first words. Pointing and maternal education emerged as predictors of lexical knowledge only in relation to a measure taken at 18 months. This suggests a far more important role for early phonological development in the creation of the lexicon than previously thought

The Role of Vocal Practice in Constructing Phonological Working Memory

Purpose: In this study, the authors looked for effects of vocal practice on phonological working memory. Method: A longitudinal design was used, combining both naturalistic observations and a nonword repetition test. Fifteen 26-month-olds (12 of whom were followed from age 11 months) were administered a nonword test including real words, "standard" nonwords (identical for all children), and nonwords based on individual children's production inventory (IN and OUT words). Results: A strong relationship was found between (a) length of experience with consonant production and (b) nonword repetition and between (a) differential experience with specific consonants through production and (b) performance on the IN versus OUT words. Conclusions: Performance depended on familiarity with words or their subunits and was strongest for real words, weaker for IN words, and weakest for OUT words. The results demonstrate the important role of speech production in the construction of phonological working memory

The influence of babbling patterns on the processing of speech

This study compared the preference of 27 British English- and 26 Welsh-learning infants for nonwords featuring consonants that occur with equal frequency in the input but that are produced either with equal frequency (Welsh) or with differing frequency (British English) in infant vocalizations. For the English infants a significant difference in looking times was related to the extent of production of the nonword consonants. The Welsh infants, who showed no production preference for either consonant, exhibited no such influence of production patterns on their response to the nonwords. The results are consistent with a previous study that suggested that pre-linguistic babbling helps shape the processing of input speech, serving as an articulatory filter that selectively makes production patterns more salient in the input. 2013 Elsevier Inc.casl36pub3229pub

In the search for stroke genes: a long and winding road

In spite of a significant improvement in control of numerous predisposing risk factors, stroke remains a major health problem and a common cause of death and disability in our societies. Genetic predisposition to stroke development exists and has been documented in both animal models and in humans. However, a precise definition of genetic factors responsible for common forms of stroke is still lacking, mainly due to its complex nature, the confounding presence of other predisposing risk factors, and the genetic heterogeneity of human populations. In contrast, important breakthroughs have been reached for monogenic forms of stroke, such as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). An animal model of stroke, the stroke-prone spontaneously hypertensive rat, has provided valuable information on genetic factors involved in stroke predisposition. Among them, the gene-encoding atrial natriuretic peptide has been identified as a stroke gene in both the stroke-prone spontaneously hypertensive rat and, subsequently, in two different human populations. In particular, structural alterations of the gene are consistently present in diseased individuals, suggesting an important role of mutation-dependent mechanisms in stroke predisposition. Finally, the recent use of intermediate disease phenotypes provides a reductionist approach that may contribute to important accumulating information on genes contributing to cerebrovascular accidents. (C) 2004 American Journal of Hypertension, Ltd

The role of accentual pattern in early lexical representation

Period of award Jun 1997 - Sep 1999Available from British Library Document Supply Centre-DSC:3739.0605(000222266) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo