133 research outputs found
Electron-ion recombination of Si IV forming Si III: Storage-ring measurement and multiconfiguration Dirac-Fock calculations
The electron-ion recombination rate coefficient for Si IV forming Si III was
measured at the heavy-ion storage-ring TSR. The experimental electron-ion
collision energy range of 0-186 eV encompassed the 2p(6) nl n'l' dielectronic
recombination (DR) resonances associated with 3s to nl core excitations, 2s
2p(6) 3s nl n'l' resonances associated with 2s to nl (n=3,4) core excitations,
and 2p(5) 3s nl n'l' resonances associated with 2p to nl (n=3,...,infinity)
core excitations. The experimental DR results are compared with theoretical
calculations using the multiconfiguration Dirac-Fock (MCDF) method for DR via
the 3s to 3p n'l' and 3s to 3d n'l' (both n'=3,...,6) and 2p(5) 3s 3l n'l'
(n'=3,4) capture channels. Finally, the experimental and theoretical plasma DR
rate coefficients for Si IV forming Si III are derived and compared with
previously available results.Comment: 13 pages, 9 figures, 3 tables. Accepted for publication in Physical
Review
7th Biennial Employment Law Institute
Materials from the 7th Biennial Employment Law Institute held by UK/CLE in June 2000
Astrophysical Relevance of Storage-Ring Electron-Ion Recombination Experiments
The relevance of storage-ring electron-ion recombination experiments for
astrophysics is outlined. In particular, the role of low-energy
dielectronic-recombination resonances is discussed. A bibliographic compilation
of electron-ion recombination measurements with cosmically abundant ions is
provided.Comment: 8 pages, 3 figures, 1 table, 77 references, Proceedings of the 14th
International Conference on the Physics of Highly Charged Ions, Cofu, Tokyo,
Septmber 1-5, 2008, to be published in J. Phys. Conf. Se
Experimental N V and Ne VIII low-temperature dielectronic recombination rate coefficients
The dielectronic recombination rate coefficients of N V and Ne VIII ions have
been measured at a heavy-ion storage ring. The investigated energy ranges
covered all dielectronic recombination resonances attached to 2s -> 2p (Delta
n=0) core excitations. The rate coefficients in a plasma are derived and
parameterized by using a convenient fit formula. The experimentally derived
rate coefficients are compared with theoretical data by Colgan et al. (2004,
A&A, 417, 1183) and Nahar & Pradhan (1997, ApJ, 111, 339) as well as with the
recommended rate coefficients by Mazzotta et al. (1998, A&A, 133, 403). The
data of Colgan et al. and Nahar & Pradhan reproduce the experiment very well
over the temperature ranges where N V and Ne VIII are expected to exist in
photoionized as well as in collisionally ionized plasmas. In contrast, the
recommendation of Mazzotta et al. agrees with the experimental rate coefficient
only in the temperature range of collisional ionization. At lower temperatures
it deviates from the measured rate coefficient by orders of magnitude. In
addition the influence of external electric fields with field strengths up to
1300 V/cm on the dielectronic recombination rate coefficient has been
investigated.Comment: 9 pages, 9 figures, to be published in Astronomy & Astrophysic
Investigation of the Role of Arg301 Identified in the X-ray Structure of Phosphite Dehydrogenase
“No, no Maama! Say ‘Shaatir ya Ouledee Shaatir’!” Children’s agency in language use and socialisation
Aims and objectives: This paper investigates how children in multilingual and transnational families mobilise their multiple and developing linguistic repertoires creatively to assert their agency in language use and socialisation, and why these acts of agency are conducive to successful maintenance of the so-called “home”, “community” or “minority” language.
Methodology: Close, qualitative analysis of mealtime multiparty conversations is carried out to examine children’s agency in language use and socialisation.
Data and analysis: Twelve hours of mealtime conversations within one Arabic and English speaking multilingual family in the UK were recorded over a period of eight months. The excerpts selected for analysis in this paper illustrate how agency is enacted in interaction.
Findings: The data analyses of the family’s language practices reveal both their flexible language policy and the importance the family attaches to Arabic. The children in this family are fully aware of the language preferences of their parents and are capable of manipulating that knowledge and asserting their agency through their linguistic choices to achieve their interactional goals.
Originality: This paper explores how Arabic is maintained as a minority language by second and third generations of Arabic-speaking immigrants in the UK through close analysis of conversations.
Significance: The findings contribute to the current discussions of family language policy and maintenance by demonstrating children’s agentive and creative roles in language use and socialisation. Three factors are identified as the reason for the successful language learning, use and maintenance of Arabic: firstly, a family language policy that has a positive multilingual outlook; secondly, family relationship dynamics that connect and bond family members; and thirdly, the children’s highly developed ability to understand their parents’ language preferences
The Properties of Adaptive Walks in Evolving Populations of Fungus
A novel method to infer the number and fitness effect of beneficial mutations reveals that the bulk of adaptive evolution is attributable to a few mutations with variable effects on fitness
Analysis of large versus small dogs reveals three genes on the canine X chromosome associated with body weight, muscling and back fat thickness
International audienceDomestic dog breeds display significant diversity in both body mass and skeletal size, resulting from intensive selective pressure during the formation and maintenance of modern breeds. While previous studies focused on the identification of alleles that contribute to small skeletal size, little is known about the underlying genetics controlling large size. We first performed a genome-wide association study (GWAS) using the Illumina Canine HD 170,000 single nucleotide polymorphism (SNP) array which compared 165 large-breed dogs from 19 breeds (defined as having a Standard Breed Weight (SBW) >41 kg [90 lb]) to 690 dogs from 69 small breeds (SBW ≤41 kg). We identified two loci on the canine X chromosome that were strongly associated with large body size at 82–84 megabases (Mb) and 101–104 Mb. Analyses of whole genome sequencing (WGS) data from 163 dogs revealed two indels in the Insulin Receptor Substrate 4 (IRS4) gene at 82.2 Mb and two additional mutations, one SNP and one deletion of a single codon, in Immunoglobulin Superfamily member 1 gene (IGSF1) at 102.3 Mb. IRS4 and IGSF1 are members of the GH/IGF1 and thyroid pathways whose roles include determination of body size. We also found one highly associated SNP in the 5’UTR of Acyl-CoA Synthetase Long-chain family member 4 (ACSL4) at 82.9 Mb, a gene which controls the traits of muscling and back fat thickness. We show by analysis of sequencing data from 26 wolves and 959 dogs representing 102 domestic dog breeds that skeletal size and body mass in large dog breeds are strongly associated with variants within IRS4, ACSL4 and IGSF1
Prior mucosal exposure to heterologous cells alters the pathogenesis of cell-associated mucosal feline immunodeficiency virus challenge
<p>Abstract</p> <p>Background</p> <p>Several lines of research suggest that exposure to cellular material can alter the susceptibility to infection by HIV-1. Because sexual contact often includes exposure to cellular material, we hypothesized that repeated mucosal exposure to heterologous cells would induce an immune response that would alter the susceptibility to mucosal infection. Using the feline immunodeficiency virus (FIV) model of HIV-1 mucosal transmission, the cervicovaginal mucosa was exposed once weekly for 12 weeks to 5,000 heterologous cells or media (control) and then cats were vaginally challenged with cell-associated or cell-free FIV.</p> <p>Results</p> <p>Exposure to heterologous cells decreased the percentage of lymphocytes in the mucosal and systemic lymph nodes (LN) expressing L-selectin as well as the percentage of CD4+ CD25+ T cells. These shifts were associated with enhanced ex-vivo proliferative responses to heterologous cells. Following mucosal challenge with cell-associated, but not cell-free, FIV, proviral burden was reduced by 64% in cats previously exposed to heterologous cells as compared to media exposed controls.</p> <p>Conclusions</p> <p>The pathogenesis and/or the threshold for mucosal infection by infected cells (but not cell-free virus) can be modulated by mucosal exposure to uninfected heterologous cells.</p
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