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Past studies have reported memory differences between monolingual and bilingual infants (Brito & Barr, 2012; Singh, Fu, Rahman, Hameed, Sanmugam, Agarwal, Jiang, Chong, Meaney & Rifkin-Graboi, 2015). A common critique within the bilingualism literature is the absence of socioeconomic indicators and/or a lack of socioeconomic diversity among participants. Previous research has demonstrated robust bilingual differences in memory generalization from 6- to 24-months of age. The goal of the current study was to examine if these findings would replicate in a sample of 18-month-old monolingual and bilingual infants from a range of socioeconomic backgrounds (N = 92). Results indicate no differences between language groups on working memory or cued recall, but significant differences for memory generalization, with bilingual infants outperforming monolingual infants regardless of socioeconomic status (SES). These findings replicate and extend results from past studies (Brito & Barr, 2012; Brito, Sebastián-Gallés & Barr, 2015) and suggest possible differential learning patterns dependent on linguistic experience.
Dysregulated physiological stress reactivity has been suggested to impact the development of children and adolescents with important health consequences throughout the life span. Both environmental adversity and genetic predispositions can lead to physiological imbalances in stress systems, which in turn lead to developmental differences. We investigated genetic and environmental contributions to autonomic nervous system reactivity to a psychosocial stressor. Furthermore, we tested whether these effects were consistent with the differential susceptibility framework. Composite measures of adverse life events combined with socioeconomic status were constructed. Effects of these adversity scores in interaction with a polygenic score summarizing six genetic variants, which were hypothesized to work as susceptibility factors, were tested on autonomic nervous system measures as indexed by heart rate and heart rate variability. Results showed that carriers of more genetic variants and exposed to high adversity manifested enhanced heart rate variability reactivity to a psychosocial stressor compared to carriers of fewer genetic variants. Conversely, the stress procedure elicited a more moderate response in these individuals compared to carriers of fewer variants when adversity was low.
In-situ ion irradiation and transmission electron microscopy has been used to examine the effects of the He appm to DPA ratio, temperature and dose on the damage structure of tungsten (W). Irradiations were performed with 15 or 60 keV He+ ions, achieving He-appm/displacements per atom (DPA) ratios of ∼40,000 and ∼2000, respectively, at temperatures between 500 and 1000°C to a dose of ∼3 DPA. A high number of small dislocation loops with sizes around 5–20 nm and a He bubble lattice were observed for both He-appm/DPA ratios at 500°C with a bubble size ∼1.5 nm. Using the g.b=0 criterion the loops were characterised as b = ±1/2<111> type. At 750°C bubbles do not form an ordered array and are larger in size compared to the irradiations at 500°C, with a diameter of ∼3 nm. Fewer dislocation loops were observed at this temperature and were also characterised to be b = ±1/2<111> type. At 1000°C, no dislocation loops were observed and bubbles grew as a function of fluence attributed to vacancy mobility being higher and vacancy clusters becoming mobile.
The MIAMI* facility at the University of Huddersfield is one of a number of facilities worldwide that permit the ion irradiation of thin foils in-situ in a transmission electron microscope. MIAMI has been developed with a particular focus on enabling the in-situ implantation of helium and hydrogen into thin electron transparent foils, necessitating ion energies in the range 1 – 10 keV. In addition, however, ions of a variety of species can be provided at energies of up to 100 keV (for singly charged ions), enabling studies to focus on the build up of radiation damage in the absence or presence of implanted gas.
This paper reports on a number of ongoing studies being carried out at MIAMI, and also at JANNuS (Orsay, France) and the IVEM / Ion Accelerator Facility (Argonne National Lab, US). This includes recent work on He bubbles in SiC and Cu; the former work concerned with modification to bubble populations by ion and electron beams and the latter project concerned with the formation of bubble super-lattices in metals.
A study is also presented consisting of experiments aimed at shedding light on the origins of the dimensional changes known to occur in nuclear graphite under irradiation with either neutrons or ions. Single crystal graphite foils have been irradiated with 60 keV Xe ions in order to create a non-uniform damage profile throughout the foil thickness. This gives rise to varying basal-plane contraction throughout the foil resulting in almost macroscopic (micron scale) deformation of the graphite. These observations are presented and discussed with a view to reconciling them with current understanding of point defect behavior in graphite.
*Microscope and Ion Accelerator for Materials Investigations
For over a decade, the structure of the inner “hole” in the transition disk around TW Hydrae has been a subject of debate. To probe the innermost regions of the protoplanetary disk, observations at the highest possible spatial resolution are required. We present new interferometric data of TW Hya from near-infrared to millimeter wavelengths. We confront existing models of the disk structure with the complete data set and develop a new, detailed radiative-transfer model. This model is characterized by: 1) a spatial separation of the largest grains from the small disk grains; and 2) a smooth inner rim structure, rather than a sharp disk edge.
The western tussock moth, Orgyia vetusta Boisduval (Lepidoptera: Lymantriidae), formerly known as Hemerocampa vetusta (Boisduval), occurs primarily in coastal areas of central California and south into Mexico, with occasional records east of the central Sacramento and San Joaquin valleys (Ferguson 1978). Two biotypes, feeding on perennial yellow bush lupine, Lupinus arboreus Sims (Fabaceae), or silver dune lupine, Lupinus chamissonis Eschsch. (this study), and on California live oak, Quercus agrifolia Née (Fagaceae), respectively, have been recognized and were originally considered two separate species (Edwards 1881; Ferguson 1978). Various fruit and nut trees have also been reported as host plants (Atkins 1958)
A brief review is given of the ways in which the local structure in glass can influence the microstructure that supports ionic transport. This in turn contributes to the co-operative nature of ion dynamics and ways in which this underpins the ‘mixed alkali effect’ are discussed. Glass microstructure too is expected to affect glass fracture as well as the chemistry of glass surfaces. In melts, though, these restrictions appear to vanish as the rigidity of intermediate range order is lost.
Between the 17th and the 21st of July, 1995 a group of about fifty mathematicians gathered in Cardiff for the Symposium on Sieve Methods, Exponential Sums and their Applications in Number Theory. They exchanged lectures and informal discussions and posed problems in the broad subject area defined by the title of the Symposium. This volume of papers gives an account of work described at the Symposium. Certain articles include a description of work done after the Symposium closed, some of this being prompted by questions posed during the Symposium.
Many of the contributions involve connections between the additive and multiplicative sides of analytic number theory, an interplay which the Symposium had been planned both to reflect and to promote. The reader will find represented here most of the branches of this subject which, as this volume demonstrates, has its roots in antiquity with the Sieve of Eratosthenes, yet is currently vibrant and receiving fresh stimulus from such diverse topics as trace formulae and elliptic curves.
Many of the participants at the Symposium were supported by the Engineering and Physical Sciences Research Council of the U.K. Others were able to bring their own support with them. The administrative costs were underwritten by the London Mathematical Society. The organisers, who are also the editors of this volume, are grateful to all the sources of support which made the Symposium possible.
The papers in this volume have been refereed to the standards required by leading journals; we take this opportunity to thank the referees for their work.
This volume comprises the proceedings of the 1995 Cardiff symposium on sieve methods, exponential sums, and their applications in number theory. Included are contributions from many leading international figures in this area which encompasses the main branches of analytic number theory. In particular, many of the papers reflect the interaction between the different fields of sieve theory, Dirichlet series (including the Riemann Zeta-function), and exponential sums, whilst displaying the subtle interplay between the additive and multiplicative aspects of the subjects. The fundamental problems discussed include recent work on Waring's problem, primes in arithmetical progressions, Goldbach numbers in short intervals, the ABC conjecture, and the moments of the Riemann Zeta-function.