1,541 research outputs found
Spatially resolved electrochemistry in ionic liquids : surface structure effects on triiodide reduction at platinum electrodes
Understanding the relationship between electrochemical activity and electrode structure is vital for improving the efficiency of dye-sensitized solar cells. Here, the reduction of triiodide to iodide in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]) room temperature ionic liquid (RTIL) is investigated on polycrystalline platinum using scanning electrochemical cell microscopy (SECCM) and correlated to the crystallographic orientation from electron backscatter diffraction (EBSD). Although the rate determining step in all grains was the first electron transfer, significant grain-dependent variations in activity were revealed, with grains with a dominant (110) crystallographic character exhibiting higher catalytic activity compared to those with a major (100) orientation. The SECCM technique is demonstrated to resolve heterogeneity in activity, highlighting that methods incorporating polycrystalline electrodes miss vital details for understanding and optimizing electrocatalysts. An additional advantage of the SECCM over single-crystal techniques is its ability to probe high index facets
Radio Pulse Properties of the Millisecond Pulsar PSR J0437-4715. I. Observations at 20cm
We present a total of 48 minutes of observations of the nearby, bright
millisecond pulsar PSR J0437-4715 taken at the Parkes radio observatory in
Australia. The data were obtained at a central radio frequency of 1380 MHz
using a high-speed tape recorder that permitted coherent Nyquist sampling of 50
MHz of bandwidth in each of two polarizations. Using the high time resolution
available from this voltage recording technique, we have studied a variety of
single-pulse properties, most for the first time in a millisecond pulsar. We
find no evidence for "diffractive" quantization effects in the individual pulse
arrival times or amplitudes as have been reported for this pulsar at lower
radio frequency using coarser time resolution (Ables et al. 1997). Overall, we
find that the single pulse properties of PSR J0437-4715 are similar to those of
the common slow-rotating pulsars, even though this pulsar's magnetosphere and
surface magnetic field are several orders of magnitude smaller than those of
the general population. The pulsar radio emission mechanism must therefore be
insensitive to these fundamental neutron star properties.Comment: 24 Postscript pages, 11 eps figures. Accepted for publication in the
Astrophysical Journal. Abbreviated abstract follow
Causes of and alternatives to medication for behaviours that challenge in people with intellectual disabilities: direct care providers' perspectives
Behaviours that challenge (BtC), such as aggression and self-injury, are manifested by many people with intellectual disabilities (ID). National and international guidelines recommend non-pharmacological psychosocial intervention before considering medication to address BtC. Support staff play a pivotal role in the prescription process. Using coproduction, we developed a training programme for support staff, called SPECTROM, to give them knowledge and empower them to question inappropriate prescriptions and ask for the discontinuation of medication if appropriate and instead look for ways to help people with ID when they are distressed without relying on medication. We have presented data from two focus groups that we conducted during the development of SPECTROM: one that included support staff, and another that had service managers and trainers. In these focus groups, we explored participants’ views on the use of medication to address BtC with a particular emphasis on the causes of and alternatives to medication for BtC. Along with the participants’ views, we have also presented how we have addressed these issues in the SPECTROM resources
Space VLBI Observations of 3C 279 at 1.6 and 5 GHz
We present the first VLBI Space Observatory Programme (VSOP) observations of
the gamma-ray blazar 3C 279 at 1.6 and 5 GHz. The combination of the VSOP and
VLBA-only images at these two frequencies maps the jet structure on scales from
1 to 100 mas. On small angular scales the structure is dominated by the quasar
core and the bright secondary component `C4' located 3 milliarcseconds from the
core (at this epoch). On larger angular scales the structure is dominated by a
jet extending to the southwest, which at the largest scale seen in these images
connects with the smallest scale structure seen in VLA images. We have
exploited two of the main strengths of VSOP: the ability to obtain
matched-resolution images to ground-based images at higher frequencies and the
ability to measure high brightness temperatures. A spectral index map was made
by combining the VSOP 1.6 GHz image with a matched-resolution VLBA-only image
at 5 GHz from our VSOP observation on the following day. The spectral index map
shows the core to have a highly inverted spectrum, with some areas having a
spectral index approaching the limiting value for synchrotron self-absorbed
radiation of 2.5. Gaussian model fits to the VSOP visibilities revealed high
brightness temperatures (>10^{12} K) that are difficult to measure with
ground-only arrays. An extensive error analysis was performed on the brightness
temperature measurements. Most components did not have measurable brightness
temperature upper limits, but lower limits were measured as high as 5x10^{12}
K. This lower limit is significantly above both the nominal inverse Compton and
equipartition brightness temperature limits. The derived Doppler factor,
Lorentz factor, and angle to the line-of-sight in the case of the equipartition
limit are at the upper end of the range of expected values for EGRET blazars.Comment: 11 pages, 6 figures, emulateapj.sty, To be published in The
Astrophysical Journal, v537, Jul 1, 200
and the Higgs mass from high scale supersymmetry
In the framework in which supersymmetry is used for understanding fermion
masses rather than stabilizing the electroweak scale, we elaborate the
phenomenological analysis for the neutrino physics. A relatively large
is the natural result. The model further predicts
vanishingly small CP violation in neutrino oscillations. And is
not necessarily maximal. While the high scale supersymmetry generically results
in a Higgs mass of about 141 GeV, our model reduces this mass via introducing
SU(2) triplet fields which also contribute to neutrino masses.Comment: 13 pages, no figure, revtex4, revised versio
A Hydrophobic Gate in an Ion Channel: The Closed State of the Nicotinic Acetylcholine Receptor
The nicotinic acetylcholine receptor (nAChR) is the prototypic member of the
`Cys-loop' superfamily of ligand-gated ion channels which mediate synaptic
neurotransmission, and whose other members include receptors for glycine,
gamma-aminobutyric acid, and serotonin. Cryo-electron microscopy has yielded a
three dimensional structure of the nAChR in its closed state. However, the
exact nature and location of the channel gate remains uncertain. Although the
transmembrane pore is constricted close to its center, it is not completely
occluded. Rather, the pore has a central hydrophobic zone of radius about 3 A.
Model calculations suggest that such a constriction may form a hydrophobic
gate, preventing movement of ions through a channel. We present a detailed and
quantitative simulation study of the hydrophobic gating model of the nicotinic
receptor, in order to fully evaluate this hypothesis. We demonstrate that the
hydrophobic constriction of the nAChR pore indeed forms a closed gate.
Potential of mean force (PMF) calculations reveal that the constriction
presents a barrier of height ca. 10 kT to the permeation of sodium ions,
placing an upper bound on the closed channel conductance of 0.3 pS. Thus, a 3 A
radius hydrophobic pore can form a functional barrier to the permeation of a 1
A radius Na+ ion. Using a united atom force field for the protein instead of an
all atom one retains the qualitative features but results in differing
conductances, showing that the PMF is sensitive to the detailed molecular
interactions.Comment: Accepted by Physical Biology; includes a supplement and a
supplementary mpeg movie can be found at
http://sbcb.bioch.ox.ac.uk/oliver/download/Movies/watergate.mp
Monitoring the Bi-Directional Relativistic Jets of the Radio Galaxy 1946+708
We report on a multi-frequency, multi-epoch campaign of Very Long Baseline
Interferometry observations of the radio galaxy 1946+708 using the VLBA and a
Global VLBI array. From these high-resolution observations we deduce the
kinematic age of the radio source to be 4000 years, comparable with the
ages of other Compact Symmetric Objects (CSOs). Ejections of pairs of jet
components appears to take place on time scales of 10 years and these
components in the jet travel outward at intrinsic velocities between 0.6 and
0.9 c. From the constraint that jet components cannot have intrinsic velocities
faster than light, we derive H_0 > 57 km s^-1 Mpc^-1 from the fastest pair of
components launched from the core. We provide strong evidence for the ejection
of a new pair of components in ~1997. From the trajectories of the jet
components we deduce that the jet is most likely to be helically confined,
rather than purely ballistic in nature.Comment: 20 pages, 8 figures, accepted to Ap
Use of evidence to support healthy public policy: a policy effectiveness-feasibility loop
Public policy plays a key role in improving population health and in the control of diseases, including non-communicable diseases.
However, an evidence-based approach to formulating healthy public policy has been difficult to implement, partly on account of barriers
that hinder integrated work between researchers and policy-makers. This paper describes a “policy effectiveness–feasibility loop” (PEFL) that
brings together epidemiological modelling, local situation analysis and option appraisal to foster collaboration between researchers and
policy-makers. Epidemiological modelling explores the determinants of trends in disease and the potential health benefits of modifying
them. Situation analysis investigates the current conceptualization of policy, the level of policy awareness and commitment among key
stakeholders, and what actually happens in practice, thereby helping to identify policy gaps. Option appraisal integrates epidemiological
modelling and situation analysis to investigate the feasibility, costs and likely health benefits of various policy options. The authors illustrate
how PEFL was used in a project to inform public policy for the prevention of cardiovascular diseases and diabetes in four parts of the eastern
Mediterranean. They conclude that PEFL may offer a useful framework for researchers and policy-makers to successfully work together to
generate evidence-based policy, and they encourage further evaluation of this approach
The long-term response of lake nutrient and chlorophyll concentrations to changes in nutrient loading in Ireland's largest lake, Lough Neagh
The long-term response of chlorophyll-a (chl-a) to changing lake water nutrient concentrations and increasing water temperature was investigated in Lough Neagh, a large, hypereutrophic lake in Northern Ireland. Trends in external and internal nutrient loading and their relation to lake nutrient concentrations were also established. Lake water concentrations of total P (TP) have increased since the 1990s but were not correlated with catchment inputs, which showed no trend. The characteristics of internal loading of P have changed since the mid-1990s, with an earlier and larger mass of P released from the sediments each summer. Catchment inputs of total oxidised N (NOx) decreased from the peak value of 10,186T/yr in 1995 to 5,396T/yr in 2011, coinciding with a reduction in lake water concentrations. External inputs and lake concentrations of NOx were highly correlated (R=0.88). Water temperature increased approximately 1C and was a predictor of variation in chl-a from 1974 to 2012. After the peak chl-a concentration in 1993, dissolved inorganic N (DIN) also became an important predictor, accounting for almost half of the 44% variance explained by a hierarchical partition model. Decreasing log (DIN:TP) ratios suggest that N limitation of chl-a has become more important in the lake recently
A new small-bodied azhdarchoid pterosaur from the Lower Cretaceous of England and its implications for pterosaur anatomy, diversity and phylogeny
BACKGROUND: Pterosaurs have been known from the Cretaceous sediments of the Isle of Wight (southern England, United Kingdom) since 1870. We describe the three-dimensional pelvic girdle and associated vertebrae of a small near-adult pterodactyloid from the Atherfield Clay Formation (lower Aptian, Lower Cretaceous). Despite acknowledged variation in the pterosaur pelvis, previous studies have not adequately sampled or incorporated pelvic characters into phylogenetic analyses. METHODOLOGY/PRINCIPAL FINDINGS: The new specimen represents the new taxon Vectidraco daisymorrisae gen. et sp. nov., diagnosed by the presence of a concavity posterodorsal to the acetabulum and the form of its postacetabular process on the ilium. Several characters suggest that Vectidraco belongs to Azhdarchoidea. We constructed a pelvis-only phylogenetic analysis to test whether the pterosaur pelvis carries a useful phylogenetic signal. Resolution in recovered trees was poor, but they approximately matched trees recovered from analyses of total evidence. We also added Vectidraco and our pelvic characters to an existing total-evidence matrix for pterosaurs. Both analyses recovered Vectidraco within Azhdarchoidea. CONCLUSIONS/ SIGNIFICANCE: The Lower Cretaceous strata of western Europe have yielded members of several pterosaur lineages, but Aptian pterosaurs from western Europe are rare. With a pelvis length of 40 mm, the new animal would have had a total length of c. 350 mm, and a wingspan of c. 750 mm. Barremian and Aptian pterodactyloids from western Europe show that small-bodied azhdarchoids lived alongside ornithocheirids and istiodactylids. This assemblage is similar in terms of which lineages are represented to the coeval beds of Liaoning, China; however, the number of species and specimens present at Liaoning is much higher. While the general phylogenetic composition of western European and Chinese communities appear to have been approximately similar, the differences may be due to different palaeoenvironmental and depositional settings. The western Europe pterodactyloid record may therefore be artificially low in diversity due to preservational factors
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