A novel application of velocity-map imaging (VMI) is demonstrated, whereby the momentum distribution of photoelectrons ejected from a tungsten nanoscale metal tip (< 50 nm radius) is recorded ...following illumination with an ultrafast laser pulse. The electrostatic conditions in the VMI instrument are optimized through finite element modelling, taking into account a physically realistic geometry including all conductive elements in the vicinity of the electron trajectories. The instrument is calibrated by observing above threshold ionization in krypton gas, and simultaneous electron emission from this gas and a tungsten nanotip is presented, illustrating that the velocity mapping condition is maintained. Realizing photoelectron VMI for femtosecond laser illuminated nanoscale objects will have a significant impact on the emerging field of ultrafast nanoplasmonics and will influence the development of such devices as a source of coherent pulses of electrons with applications in time-resolved microscopy, holography and diffractive imaging.
Review empirical research investigating the prevalence, experiences and management of hearing loss and ear disease in Aboriginal and Torres Strait Islander adults.
Scoping review.
Searches of four ...electronic databases, Advanced Google, and key webpages identified 16,373 studies − 21 met inclusion criteria: original research relating to hearing/ear health and Aboriginal and Torres Strait Islander adults.
Fourteen studies measured prevalence of hearing loss or middle-ear dysfunction, with a rate of hearing loss at an estimated 50% (reports ranging from 8% to 100%). Five studies reported views, attitudes, and experiences of hearing loss, with results showing hearing loss negatively impacted individual experiences in health and justice systems, and health professionals had limited understanding of the socioeconomic risk factors of middle ear disease. No articles directly reported on hearing loss management.
There is a lack of research into the hearing health of Aboriginal and Torres Strait Islander adults, despite its critical importance in addressing health and social inequities. Given the widely varying and imprecise estimated rates of hearing loss detected, urgent action is needed to obtain accurate prevalence estimates and, in partnership with Aboriginal and Torres Strait Islander communities, identify the best methods of screening and managing hearing loss.
Complex interventions, such as innovation platforms, pose challenges for evaluators. A variety of methodological approaches are often required to build a more complete and comprehensive understanding ...of how complex interventions work. In this paper, we outline and critically appraise a methodologically pluralist evaluation of an innovation platform to strengthen primary care for Aboriginal and Torres Strait Islander Australians. In doing so, we aim to identify lessons learned from the approach taken and add to existing literature on implementing evaluations in complex settings, such as innovation platforms. The pluralist design used four evaluation approaches-developmental evaluation, principles-focused evaluation, network analysis, and framework analysis-with differing strengths and challenges. Taken together, the multiple evaluation approaches yielded a detailed description and nuanced understanding of the formation, functioning and outcomes of the innovation platform that would be difficult to achieve with any single evaluation method. While a methodologically pluralist design may place additional pressure on logistical and analytic resources available, it enables a deeper understanding of the mechanisms that underlie complex interventions.
Polysialic acids are bioactive carbohydrates found in eukaryotes and some bacterial pathogens. The bacterial polysialyltransferases (PSTs), which catalyze the synthesis of polysialic acid capsules, ...have previously been identified in select strains of Escherichia coli and Neisseria meningitidis and are classified in the Carbohydrate-Active enZYmes Database as glycosyltransferase family GT-38. In this study using DNA sequence analysis and functional characterization we have identified a novel polysialyltransferase from the bovine/ovine pathogen Mannheimia haemolytica A2 (PSTMh). The enzyme was expressed in recombinant form as a soluble maltose-binding-protein fusion in parallel with the related PSTs from E. coli K1 and N. meningitidis group B in order to perform a side-by-side comparison. Biochemical properties including solubility, acceptor preference, reaction pH optima, thermostability, kinetics, and product chain length for the enzymes were compared using a synthetic fluorescent acceptor molecule. PSTMh exhibited biochemical properties that make it an attractive candidate for chemi-enzymatic synthesis applications of polysialic acid. The activity of PSTMh was examined on a model glycoprotein and the surface of a neuroprogenitor cell line where the results supported its development for use in applications to therapeutic protein modification and cell surface glycan remodelling to enable cell migration at implantation sites to promote wound healing. The three PSTs examined here demonstrated different properties that would each be useful to therapeutic applications.
Femtosecond vacuum ultraviolet pulses from a monochromated high harmonic generation source excite vibrational wavepackets in the state of D2. The wavepacket motion is measured through strong field ...ionization into bound and dissociative ion states yielding and D+ products. The time dependence of the and D+ ion signals provides a sensitive fingerprint of the quantum nuclear wavepacket, due to the different ionization rates for the two channels. The experiments are modelled with excitation and ionization processes included explicitly, with the results of the model showing a very good agreement with the experimental observations. The experiment demonstrates the level of detail attainable when studying ultrafast quantum nuclear dynamics using high harmonic sources.
The goal of preserving nature is often in conflict with economic development and the aspirations of the rural poor. Nowhere is this more striking than in native grasslands, which have been ...extensively converted until a mere fraction of their original extent remains. This is not surprising; grasslands flourish in places coveted by humans, primed for agriculture, plantations, and settlements that nearly always trump conservation efforts. The Umgano grassland conservation and poverty reduction project in KwaZulu-Natal Province, South Africa uses community-based spatial planning to balance the conversion of its lower-conservation value grasslands to a timber plantation, while conserving higher-value grasslands for heritage purposes and managed livestock grazing. Ten years after project launch, we measured the ecological and socioeconomic impacts of the project using Normalized Differential Vegetation Index remote sensing data and over 500 household interviews, as compared with similar non-conserved areas. Zoned management of the Umgano area had resulted in between 9% and 17% greater average peak production in the grassland areas compared to control sites. There was also a 21% gain in incomes for the roughly one hundred people employed by the forestry efforts, when compared to others in their village. Community-based spatial zoning is an overlooked tool for balancing conservation and development but may require, as we found in Umgano, certain critical factors including strong local leadership, an accountable financial management mechanism to distribute income, outside technical expertise for the zoning design, and community support.
Femtosecond electron microscopy produces real-space images of matter in a series of ultrafast snapshots. Pulses of electrons self-disperse under space-charge broadening, so without compression, the ...ideal operation mode is a single electron per pulse. Here, we demonstrate femtosecond single-electron point projection microscopy (fs-ePPM) in a laser-pump fs-e-probe configuration. The electrons have an energy of only 150 eV and take tens of picoseconds to propagate to the object under study. Nonetheless, we achieve a temporal resolution with a standard deviation of 114 fs (equivalent to a full-width at half-maximum of 269 ± 40 fs) combined with a spatial resolution of 100 nm, applied to a localized region of charge at the apex of a nanoscale metal tip induced by 30 fs 800 nm laser pulses at 50 kHz. These observations demonstrate real-space imaging of reversible processes, such as tracking charge distributions, is feasible whilst maintaining femtosecond resolution. Our findings could find application as a characterization method, which, depending on geometry, could resolve tens of femtoseconds and tens of nanometres. Dynamically imaging electric and magnetic fields and charge distributions on sub-micron length scales opens new avenues of ultrafast dynamics. Furthermore, through the use of active compression, such pulses are an ideal seed for few-femtosecond to attosecond imaging applications which will access sub-optical cycle processes in nanoplasmonics.
The evolution of pregnancy Bainbridge, David R.J
Early human development,
11/2014, Letnik:
90, Številka:
11
Journal Article
Recenzirano
Abstract Although viviparity has evolved many times in the animal kingdom, it remains relatively uncommon—scorpions and therian mammals being rare examples of entirely viviparous major taxa. ...Viviparity is a specialised form of intra-species parasitism which biases parental investment towards fertilised eggs, temporally spreads that investment, and also temporarily protects offspring from many selection pressures. Importantly, the mammalian viviparity appeared at a relatively late stage in the process of vertebrate evolution. Because of this, viviparity was ‘superimposed’ on complex pre-existing cardiovascular, respiratory, metabolic and immune systems, and has altered them dramatically. Also, pregnancy has exerted pervasive effects on gene expression in mammals, including genetic imprinting, X inactivation, sex determination, and the ectopic expression in the extra-embryonic membranes of many genes previously expressed in the gonads, brain, pituitary and immune system. Finally, although lactation probably pre-dated viviparity in mammalian evolution, the two have co-evolved as alternative strategies of offspring nutrition ever since.
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