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Sub-Doppler two-photon-excitation Rydberg spectroscopy of atomic xenon : mass-selective studies of isotopic and hyperfine structure
No full textMass-selective sub-Doppler two-photon excitation (TPE) spectroscopy is employed to resolve isotopic contributions for transitions to high-energy Rydberg levels of xenon in an atomic beam, using narrowband pulses of coherent ultraviolet light at 205–213 nm generated by nonlinear-optical conversion processes. Previous research (Kono et al 2013 J. Phys. B: At. Mol. Opt. Phys. 46 35401), has determined isotope energy shifts and hyperfine structure for 33 high-energy Rydberg levels of gas-phase xenon and accessed Rydberg levels at TPE energies in the range of 94 100–97 300 cm⁻¹ with unprecedented spectroscopic resolution. The new isotopic-mass-resolved results were obtained by adding a pulsed free-jet atomic-beam source and a mass-selective time-of-flight detector to the apparatus in order to discern individual xenon isotopes and extract previously unresolved spectroscopic information. Resulting isotope energy shifts and hyperfine-coupling parameters are examined with regard to trends in principal quantum number n and in atomic angular-momentum quantum numbers, together with empirical and theoretical precedents for such trends.15 page(s
Assessing fuel spill risks in polar waters : temporal dynamics and behaviour of hydrocarbons from Antarctic diesel, marine gas oil and residual fuel oil
No full textAs part of risk assessment of fuel oil spills in Antarctic and subantarctic waters, this study describes partitioning of hydrocarbons from three fuels (Special Antarctic Blend diesel, SAB; marine gas oil, MGO; and intermediate grade fuel oil, IFO 180) into seawater at 0 and 5 °C and subsequent depletion over 7 days. Initial total hydrocarbon content (THC) of water accommodated fraction (WAF) in seawater was highest for SAB. Rates of THC loss and proportions in equivalent carbon number fractions differed between fuels and over time. THC was most persistent in IFO 180 WAFs and most rapidly depleted in MGO WAF, with depletion for SAB WAF strongly affected by temperature. Concentration and composition remained proportionate in dilution series over time. This study significantly enhances our understanding of fuel behaviour in Antarctic and subantarctic waters, enabling improved predictions for estimates of sensitivities of marine organisms to toxic contaminants from fuels in the region.11 page(s
Physiology of reproductive worker honey bees (Apis mellifera) : insights for the development of the worker caste
No full textReproductive and behavioural specialisations characterise advanced social insect societies. Typically, the honey bee (Apis mellifera) shows a pronounced reproductive division of labour between worker and queen castes, and a clear division of colony roles among workers. In a queenless condition, however, both of these aspects of social organisation break down. Queenless workers reproduce, forage and maintain their colony operating in a manner similar to communal bees, rather than as an advanced eusocial group. This plasticity in social organisation provides a natural experiment for exploring physiological mechanisms of division of labour. We measured brain biogenic amine (BA) levels and abdominal fat body vitellogenin gene expression levels of workers in queenright and queenless colonies. Age, ovary activation and social environment influenced brain BA levels in honey bees. BA levels were most influenced by ovary activation state in queenless bees. Vitellogenin expression levels were higher in queenless workers than queenright workers, but in both colony environments vitellogenin expression was lower in foragers than non-foragers. We propose this plasticity in the interacting signalling systems that influence both reproductive and behavioural development allows queenless workers to deviate significantly from the typical worker bee reaction norm and develop as reproductively active behavioural generalists.12 page(s
Exploring how Korean teacher's attitudes and self-efficacy for using inquiry and language based teaching practices impacts learning for culturally and linguistically diverse students : implications for science teacher education
No full textDemographic trends in Korea indicate that the student population is becoming more diverse with regards to culture, ethnicity and language. These changes have implications for science classrooms where inquiry-based, student-centered activities require culturally and linguistically diverse (CLD) students to connect with their peers and successfully navigate both everyday and content specific language. This study introduces the K-TASILT (Korean Teachers' Attitudes and Self-efficacy for Inquiry and Language based Teaching) questionnaire, which we designed to investigate Korean teachers' conceptions of diversity, inquiry teaching, and language education to help explore attitudes and self-efficacy towards teaching inquiry and language skills to CLD students. An analysis of 144 primary and secondary schools teachers' responses revealed that they have fairly positive attitudes towards CLD students and positive self-efficacy for teaching inquiry, but they also have limited self-efficacy for implementing effective language teaching supports for using inquiry teaching with CLD students. We raise questions about the ways in which teachers' attitudes and beliefs about inquiry teaching and language acquisition could shape teaching practices that limit or afford opportunities for CLD students to participate in school science. We offer implications for science teacher education programs in Korea focused on enhancing diversity and content specific strategies for supporting language learning.43 page(s
Hydrodynamic simulations of the interaction between an AGB star and a main-sequence companion in eccentric orbits
No full textThe Rotten Egg Nebula has at its core a binary composed of a Mira star and an A-type companion at a separation >10 au. It has been hypothesized to have formed by strong binary interactions between the Mira and a companion in an eccentric orbit during periastron passage ~800 yr ago. We have performed hydrodynamic simulations of an asymptotic giant branch (AGB) star interacting with companions with a range of masses in orbits with a range of initial eccentricities and periastron separations. For reasonable values of the eccentricity, we find that Roche lobe overflow can take place only if the periods are ≪100 yr. Moreover, mass transfer causes the system to enter a common envelope phase within several orbits. Since the central star of the Rotten Egg nebula is an AGB star, we conclude that such a common envelope phase must have lead to a merger, so the observed companion must have been a tertiary companion of a binary that merged at the time of nebula ejection. Based on the mass and time-scale of the simulated disc formed around the companion before the common envelope phase, we analytically estimate the properties of jets that could be launched. Allowing for super-Eddington accretion rates, we find that jets similar to those observed are plausible, provided that the putative lost companion was relatively massive.15 page(s
Progressive vascular remodelling, endothelial dysfunction and stiffness in mesenteric resistance arteries in a rodent model of chronic kidney disease
No full textChronic kidney disease (CKD) and hypertension are co-morbid conditions both associated with altered resistance artery structure, biomechanics and function. We examined these characteristics in mesenteric artery together with renal function and systolic blood pressure (SBP) changes in the Lewis polycystic kidney (LPK) rat model of CKD. Animals were studied at early (6-weeks), intermediate (12-weeks), and late (18-weeks) time-points (n = 21), relative to age-matched Lewis controls (n = 29). At 12 and 18-weeks, LPK arteries exhibited eutrophic and hypertrophic inward remodelling characterised by thickened medial smooth muscle, decreased lumen diameter, and unchanged or increased media cross-sectional area, respectively. At these later time points, endothelium-dependent vasorelaxation was also compromised, associated with impaired endothelium-dependent hyperpolarisation and reduced nitric oxide synthase activity. Stiffness, elastic-modulus/stress slopes and collagen/elastin ratios were increased in 6 and 18-week-old-LPK, in contrast to greater arterial compliance at 12 weeks. Multiple linear regression analysis highlighted SBP as the main predictor of wall–lumen ratio (r = 0.536, P < 0.001 n = 46 pairs). Concentration–response curves revealed increased sensitivity to phenylephrine but not potassium chloride in 18-week-LPK. Our results indicate that impairment in LPK resistance vasculature is evident at 6 weeks, and worsens with hypertension and progression of renal disease.11 page(s
ICTs in climate change communication in the Pacific Islands
No full textCommunity participation is essential to effectively address communities' needs in relation to climate change. Conventional media forms that are easily accessible in the Pacific Islands region, including digital media, require strategic integration of both message creation and dissemination with stakeholder inclusion. This article argues that use of information and communication technologies (ICTs) not only enables information dissemination, but also invites local participation in communicative processes. Greater citizen engagement in content creation improves community understanding of the issues around climate change by including local perspectives, cultural knowledge, and concerns specific to the area. Recording, sharing, and discussing these changes in community settings will inform new thinking, with the potential to change perceptions and attitudes toward this urgent problem.12 page(s
Emerging roles of protein mannosylation in inflammation and infection
No full textProteins are frequently modified by complex carbohydrates (glycans) that play central roles in maintaining the structural and functional integrity of cells and tissues in humans and lower organisms. Mannose forms an essential building block of protein glycosylation, and its functional involvement as components of larger and diverse α-mannosidic glycoepitopes in important intra- and intercellular glycoimmunological processes is gaining recognition. With a focus on the mannose-rich asparagine (N-linked) glycosylation type, this review summarises the increasing volume of literature covering human and non-human protein mannosylation, including their structures, biosynthesis and spatiotemporal expression. The review also covers their known interactions with specialised host and microbial mannose-recognising C-type lectin receptors (mrCLRs) and antibodies (mrAbs) during inflammation and pathogen infection. Advances in molecular mapping technologies have recently revealed novel immuno-centric mannose-terminating truncated N-glycans, termed paucimannosylation, on human proteins. The cellular presentation of α-mannosidic glycoepitopes on N-glycoproteins appears tightly regulated; α-mannose determinants are relative rare glycoepitopes in physiological extracellular environments, but may be actively secreted or leaked from cells to transmit potent signals when required. Simultaneously, our understanding of the molecular basis on the recognition of mannosidic epitopes by mrCLRs including DC-SIGN, mannose receptor, mannose binding lectin and mrAb is rapidly advancing, together with the functional implications of these interactions in facilitating an effective immune response during physiological and pathophysiological conditions. Ultimately, deciphering these complex mannose-based receptor-ligand interactions at the detailed molecular level will significantly advance our understanding of immunological disorders and infectious diseases, promoting the development of future therapeutics to improve patient clinical outcomes.25 page(s
Low incident light combined with partial waterlogging impairs photosynthesis and imposes a yield penalty in cotton
No full textThrough field studies, cotton responses to dual stresses – waterlogging and low light (shade) were investigated. The hypothesis was that shade would amplify yield losses in waterlogged (WL) cotton. Either early or late in the reproductive phase, the crop was WL (96 h and 120 h, in 2012–2013 and 2013–2014, respectively) and/or shaded (6 days or 9 days in 2012–2013 and 2013–2014, respectively). Waterlogging at early reproductive phase significantly reduced lint yield (17 % averaged across both years) of cotton, although shade-induced yield losses (18 %) were only significant in 2013–2014. Shade significantly exacerbated yield losses only when the impact of waterlogging damage was modest (2013–2014). More intense waterlogging impaired lint yield independently of the light levels. Yield reductions in these experiments were the consequence of both accelerated fruit abscission and fewer fruiting nodes produced. Plants had lower leaf nitrogen levels and photosynthetic rates after waterlogging and/or shade treatments and produced fewer fruiting nodes. Although long-term shade increased specific leaf area (30 %) and leaf N (20 %) immediately following 5 days of waterlogging, it did not restore shoot growth, node formation or lint yield because of suppressed photosynthetic performance (area basis) and carbohydrate supply.11 page(s