An enduring problem in North American archaeology concerns the nature of the transition between the Clovis and Folsom Paleoindian complexes in the West. Traditional models indicate a temporal hiatus between the two complexes implying that Folsom was a population replacement for Clovis. Alternatively, if Folsom was an innovation that occurred within Clovis populations and subsequently spread, we would expect to see a temporal overlap. Here, we test these hypotheses using high-quality radiocarbon dates and Bayesian statistics to infer the temporal boundaries of the complexes. We show that the Folsom complex initially appears between 12,900 and 12,740 cal BP, whereas Clovis disappears between 12,720 and12,490 cal BP. Therefore, Folsom may have appeared about 200 years before Clovis disappeared, and so the two complexes likely co-occurred in the West for nearly eight generations. This finding suggests that Folsom was a successful adaptive innovation that diffused through the western Clovis population, eventually going to fixation over multiple generations.

The literature of recent UK policy toward Syria focuses on the 2013 chemical weapons crisis. We examine policy discourses leading up to that. The government supported the removal of Assad but faced the challenge of explaining how that would be realised. Given its unwillingness and inability to mobilise support for military intervention, or to tailor policy goals to match available means, government strategy arguably lacked credibility. Our purpose is to examine how the government tried to close this ends means gap and how, having failed to do that, its ‘discursive strategy’ legitimised its approach. We argue the resources for the government’s discursive strategy on Syria can be found in the earlier articulation of ‘liberal conservatism’. A policy that from an ideal-liberal or ideal-conservative position might have been criticised as half-baked was maintained by a strategy that gave consideration to, but did not completely follow through on, either archetype. Drawing on an analysis of 2,152 sources and supplemented by elite interviews, we illustrate how this strategy managed the interplay of two basic discourses: a liberal insistence that the UK should support ‘the Arab Spring’ and a conservative insistence that military intervention was imprudent because ‘Syria was not Libya’.

Objective: Individuals in the helping professions are subject to unique stressors that may lead to burnout, and research has shown that those who work with dying or bereaved individuals might be particularly at-risk. This study explores how factors such as spirituality and level of training might buffer the stress of working with terminally ill clients and their families.

Method: A total of 80 medical and mental health practitioners attending palliative care seminars were surveyed, with each completing validated measures of daily spiritual experiences and caregiver burnout, as well as assessments of demographic factors, their general education and training experiences specific to working in end-of-life care and bereavement settings.

Results: Findings indicate that daily spiritual experiences might mitigate physical, cognitive, and emotional forms of burnout in the workplace. In addition, a negative correlation was found between the amount of end-of-life training received and burnout in the physical and cognitive domains. However, training was not related to professionals' level of emotional exhaustion.

Significance of the research: Results reinforce a growing literature on the salutary effects of spirituality, and underscore its relevance as one possible form of constructive coping for professionals attending to the needs of the dying and bereaved. The study carries further implications for how the stresses of such work might be ameliorated by enhanced training efforts, as well as creative facilitation of diverse spiritual expressions (e.g., inclusive forms of ritual recognition of loss) in the workplace.

RNA helices that recapitulate sequences of the tRNA acceptor stem, including the 3′ NCCA nucleotides, can be substrates for aminoacyl–tRNA synthetases (Frugier et al., 1994; Hamann & Hou, 1995; Martinis & Schimmel, 1995; Quinn et al., 1995). Although the catalytic efficiency of aminoacylation of RNA helices is reduced from that of the full-length parent tRNA, the specificity is maintained. The specific aminoacylation lies in the ability of aminoacyl–tRNA synthetases to recognize functional groups within the RNA helices. Analysis of tRNA–synthetase structures has suggested a general principle (Rould et al., 1989; Ruff et al., 1991; Arnez & Moras, 1997). The class I synthetases, which attach an amino acid initially to the 2′-OH of the terminal ribose, approach the acceptor and NCCA end from the minor groove side. The class II synthetases, which attach an amino acid to the terminal 3′-OH, approach from the major groove side (Arnez & Moras, 1997). The class-specific approach leads to tRNA–synthetase complexes that are near mirror images of each other and provides a structural rationale for the stereochemistries of aminoacylation. We report here the identification of a functional group in the acceptor end of Escherichia coli tRNACys that is important for the class I cysteine–tRNA synthetase. This functional group makes one of the largest energetic contributions to aminoacylation. However, it is located on the major groove side of the acceptor stem. Kinetic analysis of the contribution of this functional group to aminoacylation suggests new features that are not anticipated from the class-specific approach of synthetases.

The RNA pseudoknot located at the 5′ end of the gene 32 messenger RNA of bacteriophage T2 contains two A-form helical stems connected by two loops, in an H-type pseudoknot topology. A combination of multidimensional NMR methods and isotope labeling were used to investigate the pseudoknot structure, resulting in a more detailed structural model than provided by earlier homonuclear NMR studies. Of particular significance, the interface between the stacked helical stems within the pseudoknot motif is described in detail. The two stems are stacked in a coaxial manner, with an approximately 18° rotation of stem1 relative to stem2 about an axis that is parallel to the helical axis. This rotation serves to relieve what would otherwise be a relatively close phosphate–phosphate contact at the junction of the two stems, while preserving the stabilizing effects of base stacking. The ability of the NMR data to determine pseudoknot bending was critically assessed. The data were found to be a modestly precise indicator of pseudoknot bending, with the angle between the helical axes of stem1 and stem2 being in the range of 15 ± 15°. Pseudoknot models with bend angles within this range are equally consistent with the data, since they differ by only small amounts in the relatively short-range interproton distances from which the structure was derived. The gene 32 messenger RNA pseudoknot was compared with other RNA structures with coaxial or near-coaxial stacked helical stems.