412 research outputs found
Quantifying the stability of planktic foraminiferal physical niches between the Holocene and Last Glacial Maximum
Probing deeper into the risks of slips, trips and falls for an ageing rail passenger population: applying a systems approach
In this study, the authors report the findings from a study of the contributory factors leading to slips, trips and falls (STFs) amongst elderly passengers at train stations and how these are likely to change in the future over the medium to long term (the period 2035–2050). Their data draws on: stakeholder interviews with rail personnel and elderly passengers; a set of station observations carried out across the UK; and, a survey of the views of station managers. The findings point to a set of 22 contributory factors covering aspects of organisational, station environment and passenger (individual) influence on STFs. Amongst the factors which most concern station managers at the present and over the next few decades are: rushing behaviour on train platforms; the consumption of alcohol by passengers; aspects of station design (e.g. flooring); and, training for station staff as regard the risks of STFs. The authors summarise their findings in the form of a systems model which highlights priorities with regard to STFs in terms of all of the stakeholders taking part in the study. A final section discusses a set of issues which might form the basis for a future agenda for research and practice in this area
A Computational and Experimental Study on the Binding of Dithio Ligands to Sperrylite, Pentlandite, and Platinum
Antimalarial drug discovery - the path towards eradication
Malaria is a disease that still affects a significant proportion of the global human population. Whilst advances have been made in lowering the numbers of cases and deaths, it is clear that a strategy based solely on disease control year on year, without reducing transmission and ultimately eradicating the parasite, is unsustainable. This article highlights the current mainstay treatments alongside a selection of emerging new clinical molecules from the portfolio of Medicines for Malaria Venture (MMV) and our partners. In each case, the key highlights from each research phase are described to demonstrate how these new potential medicines were discovered. Given the increased focus of the community on eradicating the disease, the strategy for next generation combination medicines that will provide such potential is explaine
First-Principles Study on Ligand Binding and Positional Disorder in Pentlandite
Density
functional theory, in conjunction with a cluster expansion
model, has been used to study the structure and stability of the positionally
disordered iron–nickel sulfide mineral pentlandite (Pn), (Fe,Ni)<sub>9</sub>S<sub>8</sub>, with results indicating heterogeneous nearest
neighbor metal contacts are more energetically favorable than homogeneous
contacts. The virtual crystal approximation was also explored as a
means to address positional disorder, but while reliable results could
be obtained for the bulk model, the same was not true for the surface,
as local distortions which affected the surface model energies could
not be reproduced. We also address the binding of ethyl xanthate (CH<sub>3</sub>CH<sub>2</sub>OCS<sub>2</sub><sup>–</sup>), water,
and hydroxide to the [111] Pn surface to understand the mode of action
of industrial xanthate flotation agents better. In order to model
anionic ligands bound to a periodic boundary condition surface we
propose applying a correction derived from the surface work function
to remove the additional charge introduced by the ligand. The results
obtained from the ligand binding studies indicate that while ethyl
xanthate could readily displace up to a full monolayer of water per
unit cell it is likely that Fe-enriched surfaces will bind xanthate
in competition with the hydroxide anion, while a Ni-enriched surface
will preferentially bind hydroxide anions over xanthate
Sect and House in Syria: History, Architecture, and Bayt Amongst the Druze in Jaramana
This paper explores the connections between the architecture and materiality of houses and the social idiom of bayt (house, family). The ethnographic exploration is located in the Druze village of Jaramana, on the outskirts of the Syrian capital Damascus. It traces the histories, genealogies, and politics of two families, bayt Abud-Haddad and bayt Ouward, through their houses. By exploring the two families and the architecture of their houses, this paper provides a detailed ethnographic account of historical change in modern Syria, internal diversity, and stratification within the intimate social fabric of the Druze neighbourhood at a time of war, and contributes a relational approach to the anthropological understanding of houses
Polyolefin–polar block copolymers from versatile new macromonomers
A new metallocene-based polymerization mechanism is elucidated in which a zirconium hydride center inserts α-methylstyrene at the start of a polymer chain. The hydride is then regenerated by hydrogenation to release a polyolefin containing a single terminal α-methylstyrenyl group. Through the use of the difunctional monomer 1,3-diisopropenylbenzene, this catalytic hydride insertion polymerization is applied to the production of linear polyethylene and ethylene–hexene copolymers containing an isopropenylbenzene end group. Conducting simple radical polymerizations in the presence of this new type of macromonomer leads to diblock copolymers containing a polyolefin attached to an acrylate, methacrylate, vinyl ester, or styrenic segments. The new materials are readily available and exhibit interfacial phenomena, including the mediation of the mixing of immiscible polymer blends
100 million years of turtle paleoniche dynamics enable the prediction of latitudinal range shifts in a warming world
Past responses to environmental change provide vital baseline data for estimating the potential resilience of extant taxa to future change. Here, we investigate the latitudinal range contraction that terrestrial and freshwater turtles (Testudinata) experienced from the Late Cretaceous to the Paleogene (100.5-23.03 mya) in response to major climatic changes. We apply ecological niche modeling (ENM) to reconstruct turtle niches, using ancient and modern distribution data, paleogeographic reconstructions, and the HadCM3L climate model to quantify their range shifts in the Cretaceous and late Eocene. We then use the insights provided by these models to infer their probable ecological responses to future climate scenarios at different representative concentration pathways (RCPs 4.5 and 8.5 for 2100), which project globally increased temperatures and spreading arid biomes at lower to mid-latitudes. We show that turtle ranges are predicted to expand poleward in the Northern Hemisphere, with decreased habitat suitability at lower latitudes, inverting a trend of latitudinal range contraction that has been prevalent since the Eocene. Trionychids and freshwater turtles can more easily track their niches than Testudinidae and other terrestrial groups. However, habitat destruction and fragmentation at higher latitudes will probably reduce the capability of turtles and tortoises to cope with future climate changes
WSClean : an implementation of a fast, generic wide-field imager for radio astronomy
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.Astronomical widefield imaging of interferometric radio data is computationally expensive, especially for the large data volumes created by modern non-coplanar many-element arrays. We present a new widefield interferometric imager that uses the w-stacking algorithm and can make use of the w-snapshot algorithm. The performance dependencies of CASA's w-projection and our new imager are analysed and analytical functions are derived that describe the required computing cost for both imagers. On data from the Murchison Widefield Array, we find our new method to be an order of magnitude faster than w-projection, as well as being capable of full-sky imaging at full resolution and with correct polarisation correction. We predict the computing costs for several other arrays and estimate that our imager is a factor of 2-12 faster, depending on the array configuration. We estimate the computing cost for imaging the low-frequency Square-Kilometre Array observations to be 60 PetaFLOPS with current techniques. We find that combining w-stacking with the w-snapshot algorithm does not significantly improve computing requirements over pure w-stacking. The source code of our new imager is publicly released.Peer reviewedFinal Published versio
SN 2009kf : a UV bright type IIP supernova discovered with Pan-STARRS 1 and GALEX
We present photometric and spectroscopic observations of a luminous type IIP
Supernova 2009kf discovered by the Pan-STARRS 1 (PS1) survey and detected also
by GALEX. The SN shows a plateau in its optical and bolometric light curves,
lasting approximately 70 days in the rest frame, with absolute magnitude of M_V
= -18.4 mag. The P-Cygni profiles of hydrogen indicate expansion velocities of
9000km/s at 61 days after discovery which is extremely high for a type IIP SN.
SN 2009kf is also remarkably bright in the near-ultraviolet (NUV) and shows a
slow evolution 10-20 days after optical discovery. The NUV and optical
luminosity at these epochs can be modelled with a black-body with a hot
effective temperature (T ~16,000 K) and a large radius (R ~1x10^{15} cm). The
bright bolometric and NUV luminosity, the lightcurve peak and plateau duration,
the high velocities and temperatures suggest that 2009kf is a type IIP SN
powered by a larger than normal explosion energy. Recently discovered high-z
SNe (0.7 < z < 2.3) have been assumed to be IIn SNe, with the bright UV
luminosities due to the interaction of SN ejecta with a dense circumstellar
medium (CSM). UV bright SNe similar to SN 2009kf could also account for these
high-z events, and its absolute magnitude M_NUV = -21.5 +/- 0.5 mag suggests
such SNe could be discovered out to z ~2.5 in the PS1 survey.Comment: Accepted for publication in APJ
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